Merge branch 'ollama:main' into main

2025-12-21 14:26:30 +00:00 · 2025-03-02 13:45:52 +08:00
parent 1f7de23036 21aa666a1e
commit 92731dfc6f
19 changed files with 665 additions and 273 deletions
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -122,9 +122,11 @@ if(CMAKE_HIP_COMPILER)
        add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/ml/backend/ggml/ggml/src/ggml-hip)

        if (WIN32)
-            target_compile_definitions(ggml-hip PRIVATE GGML_CUDA_NO_PEER_COPY=1)
+            target_compile_definitions(ggml-hip PRIVATE GGML_CUDA_NO_PEER_COPY)
        endif()

+        target_compile_definitions(ggml-hip PRIVATE GGML_HIP_NO_VMM)
+
        set(OLLAMA_HIP_INSTALL_DIR ${OLLAMA_INSTALL_DIR}/rocm)
        install(TARGETS ggml-hip
            RUNTIME_DEPENDENCIES
--- a/kvcache/cache.go
+++ b/kvcache/cache.go
@@ -29,6 +29,17 @@ type Cache interface {
 	// cache implementation used.
 	Put(ctx ml.Context, key, value ml.Tensor)

+	// SetConfig controls optimizations (mostly backend-specific) that may transform
+	// the output of the cache to work better with specific kernels. If not called,
+	// the backend settings will be used. This works well when calling Attention.
+	//
+	// The config can be overridden by models, especially if they require vanilla
+	// output when implementing their own version of attention. To do this, pass
+	// an empty ml.CacheConfig.
+	//
+	// Most models will not need to use this.
+	SetConfig(ml.CacheConfig)
+
 	// ** cache management **

 	// Init sets up runtime parameters
--- a/kvcache/causal.go
+++ b/kvcache/causal.go
@@ -22,6 +22,9 @@ type Causal struct {
 	Capacity   int32
 	windowSize int32

+	// config controls mostly backend-specific optimizations
+	config *ml.CacheConfig
+
 	// ** current forward pass **

 	// the active layer for Get and Put
@@ -75,14 +78,42 @@ func NewSWACache(windowSize int32, shift shiftFn) *Causal {
 }

 func (c *Causal) Init(backend ml.Backend, dtype ml.DType, capacity int32) {
+	if c.config == nil {
+		var config ml.CacheConfig
+		if cc, ok := backend.(ml.BackendCacheConfig); ok {
+			config = cc.CacheConfig()
+		}
+		c.config = &config
+	}
+
+	if c.config.CachePadding == 0 {
+		c.config.CachePadding = 1
+	}
+
+	if c.config.MaskBatchPadding == 0 {
+		c.config.MaskBatchPadding = 1
+	}
+
+	if c.config.MaskDType == ml.DTypeOther {
+		c.config.MaskDType = ml.DTypeF32
+	}
+
 	c.DType = dtype
-	c.Capacity = capacity
-	c.cells = make([]cacheCell, capacity)
+	c.Capacity = int32(roundUp(int(capacity), c.config.CachePadding))
+	c.cells = make([]cacheCell, c.Capacity)
 	c.cellRanges = make(map[int]cellRange)
 	c.backend = backend
 	c.cacheCtx = backend.NewContext()
 }

+func (c *Causal) SetConfig(config ml.CacheConfig) {
+	if c.config != nil {
+		panic("config cannot be changed after being previously set, either by the model or backend")
+	}
+
+	c.config = &config
+}
+
 func (c *Causal) Close() {
 	c.cacheCtx.Close()
 }
@@ -157,36 +188,91 @@ func (c *Causal) findStartLoc() (int, error) {
 	return 0, fmt.Errorf("%w (length: %v)", ErrKvCacheFull, c.Capacity)
 }

+func roundDown(length, pad int) int {
+	return (length / pad) * pad
+}
+
+func roundUp(length, pad int) int {
+	return ((length + pad - 1) / pad) * pad
+}
+
 // Builds a mask of history x batch indicating whether for each token in the batch the
 // token in the history should apply. This is based on both the sequence and causality (the
 // position of the history is not ahead of the token in the batch).
 func (c *Causal) buildMask(ctx ml.Context, positions []int32, seqs []int) (ml.Tensor, error) {
-	// TODO(jessegross): This does not do padding, which is required for flash attention
-	len := c.curCellRange.max - c.curCellRange.min + 1
-	mask := make([]float32, c.curBatchSize*len)
+	// Align and pad the two dimensions as required by the backend
+	batchSize := roundUp(c.curBatchSize, c.config.MaskBatchPadding)
+
+	c.curCellRange.min = roundDown(c.curCellRange.min, c.config.CachePadding)
+	c.curCellRange.max = roundUp(c.curCellRange.max+1, c.config.CachePadding) - 1
+
+	length := c.curCellRange.max - c.curCellRange.min + 1
+	mask := make([]float32, batchSize*length)

 	for i := range c.curBatchSize {
 		for j := c.curCellRange.min; j <= c.curCellRange.max; j++ {
 			if !slices.Contains(c.cells[j].sequences, seqs[i]) || c.cells[j].pos > positions[i] ||
 				c.cells[j].pos < positions[i]-c.windowSize {
-				mask[i*len+(j-c.curCellRange.min)] = float32(math.Inf(-1))
+				mask[i*length+(j-c.curCellRange.min)] = float32(math.Inf(-1))
 			}
 		}
 	}

-	return ctx.FromFloatSlice(mask, len, c.curBatchSize)
+	// Mask out any padding tokens we added. For padding that we added to the cache history, this
+	// has already been masked out because the sequence doesn't match.
+	for i := c.curBatchSize * length; i < len(mask); i++ {
+		mask[i] = float32(math.Inf(-1))
+	}
+
+	maskTensor, err := ctx.FromFloatSlice(mask, length, batchSize)
+	if err != nil {
+		return nil, err
+	}
+
+	if c.config.MaskDType != ml.DTypeF32 {
+		out := ctx.Empty(c.config.MaskDType, maskTensor.Shape()...)
+		ctx.Forward(maskTensor.Copy(ctx, out))
+		maskTensor = out
+	}
+
+	return maskTensor, nil
 }

-func moveCell(ctx ml.Context, objs []ml.Tensor, src, dst, len int) {
-	for _, obj := range objs {
-		if obj == nil {
+func (c *Causal) moveCells(ctx ml.Context, src, dst, len int) {
+	for i := range c.keys {
+		if c.keys[i] == nil {
 			continue
 		}

-		srcView := obj.View(ctx, obj.Stride(2)*src, obj.Dim(0)*obj.Dim(1)*len)
-		dstView := obj.View(ctx, obj.Stride(2)*dst, obj.Dim(0)*obj.Dim(1)*len)
+		key := c.keys[i]

-		ctx.Forward(srcView.Copy(ctx, dstView))
+		kHeadDim := key.Dim(0)
+		numKVHeads := key.Dim(1)
+		rowSize := key.Stride(2)
+
+		kSrcView := key.View(ctx, rowSize*src, kHeadDim*numKVHeads*len)
+		kDstView := key.View(ctx, rowSize*dst, kHeadDim*numKVHeads*len)
+
+		value := c.values[i]
+		var vSrcView, vDstView ml.Tensor
+		if c.config.PermutedV {
+			vHeadDim := value.Dim(1)
+			elemSize := value.Stride(0)
+
+			vSrcView = value.View(ctx, elemSize*src, len, int(c.Capacity)*elemSize, vHeadDim*numKVHeads)
+			vDstView = value.View(ctx, elemSize*dst, len, int(c.Capacity)*elemSize, vHeadDim*numKVHeads)
+		} else {
+			vHeadDim := value.Dim(0)
+			rowSize := value.Stride(2)
+
+			vSrcView = value.View(ctx, rowSize*src, vHeadDim*numKVHeads*len)
+			vDstView = value.View(ctx, rowSize*dst, vHeadDim*numKVHeads*len)
+		}
+
+		ctx.Forward(
+			kSrcView.Copy(ctx, kDstView),
+			vSrcView.Copy(ctx, vDstView),
+		)
 	}
 }

@@ -238,8 +324,7 @@ func (c *Causal) defrag() {
 							pendingLen++
 							break
 						} else {
-							moveCell(ctx, c.keys, pendingSrc, pendingDst, pendingLen)
-							moveCell(ctx, c.values, pendingSrc, pendingDst, pendingLen)
+							c.moveCells(ctx, pendingSrc, pendingDst, pendingLen)
 							moves++
 						}
 					}
@@ -263,8 +348,7 @@ func (c *Causal) defrag() {
 	}

 	if pendingLen > 0 {
-		moveCell(ctx, c.keys, pendingSrc, pendingDst, pendingLen)
-		moveCell(ctx, c.values, pendingSrc, pendingDst, pendingLen)
+		c.moveCells(ctx, pendingSrc, pendingDst, pendingLen)
 		moves++
 	}

@@ -305,35 +389,73 @@ func (c *Causal) Get(ctx ml.Context) (ml.Tensor, ml.Tensor, ml.Tensor) {
 	key := c.keys[c.curLayer]
 	value := c.values[c.curLayer]

-	key = key.View(ctx, key.Stride(2)*c.curCellRange.min,
-		key.Dim(0), key.Stride(1),
-		key.Dim(1), key.Stride(2),
-		c.curMask.Dim(0),
+	kHeadDim := key.Dim(0)
+	numKVHeads := key.Dim(1)
+	rowSize := key.Stride(2)
+	cachedSize := c.curMask.Dim(0)
+
+	key = key.View(ctx, rowSize*c.curCellRange.min,
+		kHeadDim, key.Stride(1),
+		numKVHeads, key.Stride(2),
+		cachedSize,
 	)

-	value = value.View(ctx, key.Stride(2)*c.curCellRange.min,
-		value.Dim(0), value.Stride(1),
-		value.Dim(1), value.Stride(2),
-		c.curMask.Dim(0),
-	)
+	if c.config.PermutedV {
+		vHeadDim := value.Dim(1)
+		elemSize := value.Stride(0)
+
+		value = value.View(ctx, elemSize*c.curCellRange.min,
+			cachedSize, value.Stride(1),
+			vHeadDim, value.Stride(2),
+			numKVHeads,
+		)
+	} else {
+		vHeadDim := value.Dim(0)
+		rowSize := value.Stride(2)
+
+		value = value.View(ctx, rowSize*c.curCellRange.min,
+			vHeadDim, value.Stride(1),
+			numKVHeads, value.Stride(2),
+			cachedSize,
+		)
+	}

 	return key, value, c.curMask
 }

 func (c *Causal) Put(ctx ml.Context, key, value ml.Tensor) {
-	if c.curBatchSize != key.Dim(2) {
-		panic(fmt.Errorf("inconsistent batch sizes (layer: %v, batch size: %v layer batch size: %v)", c.curLayer, c.curBatchSize, key.Dim(2)))
+	kHeadDim := key.Dim(0)
+	vHeadDim := value.Dim(0)
+	numKVHeads := key.Dim(1)
+	batchSize := key.Dim(2)
+
+	if c.curBatchSize != batchSize {
+		panic(fmt.Errorf("inconsistent batch sizes (layer: %v, batch size: %v layer batch size: %v)", c.curLayer, c.curBatchSize, batchSize))
 	}

 	if c.keys[c.curLayer] == nil || c.values[c.curLayer] == nil {
-		c.keys[c.curLayer] = c.cacheCtx.Zeros(c.DType, key.Dim(0), key.Dim(1), int(c.Capacity))
-		c.values[c.curLayer] = c.cacheCtx.Zeros(c.DType, value.Dim(0), value.Dim(1), int(c.Capacity))
+		c.keys[c.curLayer] = c.cacheCtx.Zeros(c.DType, kHeadDim, numKVHeads, int(c.Capacity))
+
+		if c.config.PermutedV {
+			c.values[c.curLayer] = c.cacheCtx.Zeros(c.DType, int(c.Capacity), vHeadDim, numKVHeads)
+		} else {
+			c.values[c.curLayer] = c.cacheCtx.Zeros(c.DType, vHeadDim, numKVHeads, int(c.Capacity))
+		}
 	}

-	ctx.Forward(
-		key.Copy(ctx, c.keys[c.curLayer].View(ctx, c.keys[c.curLayer].Stride(2)*c.curLoc, key.Dim(0)*key.Dim(1)*key.Dim(2))),
-		value.Copy(ctx, c.values[c.curLayer].View(ctx, c.values[c.curLayer].Stride(2)*c.curLoc, value.Dim(0)*value.Dim(1)*value.Dim(2))),
-	)
+	rowSize := c.keys[c.curLayer].Stride(2)
+	ctx.Forward(key.Copy(ctx, c.keys[c.curLayer].View(ctx, rowSize*c.curLoc, kHeadDim*numKVHeads*batchSize)))
+
+	if c.config.PermutedV {
+		elemSize := c.values[c.curLayer].Stride(0)
+
+		value = value.Permute(ctx, 1, 2, 0, 3)
+		ctx.Forward(value.Copy(ctx, c.values[c.curLayer].View(ctx, elemSize*c.curLoc, batchSize, int(c.Capacity)*elemSize, vHeadDim*numKVHeads)))
+	} else {
+		rowSize := c.values[c.curLayer].Stride(2)
+
+		ctx.Forward(value.Copy(ctx, c.values[c.curLayer].View(ctx, rowSize*c.curLoc, vHeadDim*numKVHeads*batchSize)))
+	}
 }

 func (c *Causal) CopyPrefix(srcSeq, dstSeq int, len int32) {
@@ -389,9 +511,13 @@ func (c *Causal) shift(seq int, beginIndex, offset int32) error {
 			continue
 		}

-		key = key.View(ctx, key.Stride(2)*seqRange.min,
-			key.Dim(0), key.Stride(1),
-			key.Dim(1), key.Stride(2),
+		kHeadDim := key.Dim(0)
+		numKVHeads := key.Dim(1)
+		rowSize := key.Stride(2)
+
+		key = key.View(ctx, rowSize*seqRange.min,
+			kHeadDim, key.Stride(1),
+			numKVHeads, key.Stride(2),
 			size,
 		)

--- a/kvcache/causal_test.go
+++ b/kvcache/causal_test.go
@@ -309,7 +309,7 @@ func (b *testBackend) SystemInfo() string {

 type testContext struct{}

-func (c *testContext) Zeros(dtype ml.DType, shape ...int) ml.Tensor {
+func (c *testContext) Empty(dtype ml.DType, shape ...int) ml.Tensor {
 	total := 0

 	if len(shape) > 0 {
@@ -322,8 +322,12 @@ func (c *testContext) Zeros(dtype ml.DType, shape ...int) ml.Tensor {
 	return &testTensor{dtype: dtype, elementSize: 4, data: make([]float32, total), shape: shape}
 }

+func (c *testContext) Zeros(dtype ml.DType, shape ...int) ml.Tensor {
+	return c.Empty(dtype, shape...)
+}
+
 func (c *testContext) FromFloatSlice(s []float32, shape ...int) (ml.Tensor, error) {
-	t := c.Zeros(ml.DTypeF32, shape...).(*testTensor)
+	t := c.Empty(ml.DTypeF32, shape...).(*testTensor)

 	copy(t.data, s)

@@ -391,7 +395,7 @@ func (t *testTensor) Floats() []float32 {
 }

 func (t *testTensor) Add(ctx ml.Context, t2 ml.Tensor) ml.Tensor {
-	out := ctx.Zeros(t.DType(), t.Shape()...).(*testTensor)
+	out := ctx.Empty(t.DType(), t.Shape()...).(*testTensor)

 	for i := range out.data {
 		out.data[i] = t.data[i] + t2.(*testTensor).data[i]
@@ -468,7 +472,7 @@ func (t *testTensor) View(ctx ml.Context, offset int, shape ...int) ml.Tensor {

 	context := &testContext{}

-	view := context.Zeros(t.dtype, s...).(*testTensor)
+	view := context.Empty(t.dtype, s...).(*testTensor)
 	view.data = t.data[offset : offset+len(view.data)]

 	return view
--- a/kvcache/encoder.go
+++ b/kvcache/encoder.go
@@ -1,6 +1,8 @@
 package kvcache

 import (
+	"fmt"
+
 	"github.com/ollama/ollama/ml"
 )

@@ -11,6 +13,9 @@ import (
 //
 // Not currently safe for multiple sequences
 type EncoderCache struct {
+	// config controls mostly backend-specific optimizations
+	config *ml.CacheConfig
+
 	// ** current forward pass **

 	// the active layer for Get and Put
@@ -40,9 +45,29 @@ func NewEncoderCache() *EncoderCache {
 }

 func (c *EncoderCache) Init(backend ml.Backend, dtype ml.DType, capacity int32) {
+	if c.config == nil {
+		var config ml.CacheConfig
+		if cc, ok := backend.(ml.BackendCacheConfig); ok {
+			config = cc.CacheConfig()
+		}
+		c.config = &config
+	}
+
+	if c.config.CachePadding != 0 && c.config.CachePadding != 1 {
+		panic(fmt.Errorf("encoder cache is unable to enforce requested CachePadding (%v)", c.config.CachePadding))
+	}
+
 	c.cacheCtx = backend.NewContext()
 }

+func (c *EncoderCache) SetConfig(config ml.CacheConfig) {
+	if c.config != nil {
+		panic("config cannot be changed after being previously set, either by the model or backend")
+	}
+
+	c.config = &config
+}
+
 func (c *EncoderCache) Close() {
 	c.cacheCtx.Close()
 }
@@ -75,9 +100,13 @@ func (c *EncoderCache) Put(ctx ml.Context, key, value ml.Tensor) {
 	c.encoderPos = c.curPos
 	c.encoderCached = true

+	if c.config.PermutedV {
+		value = value.Permute(ctx, 1, 2, 0, 3)
+	}
+
 	if c.keys[c.curLayer] == nil || c.values[c.curLayer] == nil {
-		c.keys[c.curLayer] = c.cacheCtx.Zeros(key.DType(), key.Shape()...)
-		c.values[c.curLayer] = c.cacheCtx.Zeros(value.DType(), value.Shape()...)
+		c.keys[c.curLayer] = c.cacheCtx.Empty(key.DType(), key.Shape()...)
+		c.values[c.curLayer] = c.cacheCtx.Empty(value.DType(), value.Shape()...)
 	}

 	ctx.Forward(
--- a/kvcache/wrapper.go
+++ b/kvcache/wrapper.go
@@ -28,6 +28,12 @@ func (c *WrapperCache) Init(backend ml.Backend, dtype ml.DType, capacity int32)
 	}
 }

+func (c *WrapperCache) SetConfig(config ml.CacheConfig) {
+	for _, cache := range c.caches {
+		cache.SetConfig(config)
+	}
+}
+
 func (c *WrapperCache) Close() {
 	for _, cache := range c.caches {
 		cache.Close()
--- a/ml/backend.go
+++ b/ml/backend.go
@@ -27,6 +27,35 @@ type Backend interface {
 	SystemInfo() string
 }

+// BackendCacheConfig should be implemented by backends that need special output
+// from the cache to meet specific requirements. It is frequently implemented in
+// conjunction with ScaledDotProductAttention.
+type BackendCacheConfig interface {
+	CacheConfig() CacheConfig
+}
+
+// CacheConfig controls optimizations (mostly backend-specific) that may transform
+// the output the cache to work better with specific kernels.
+type CacheConfig struct {
+	// CachePadding specifies the multiple for the number of tokens of cache history
+	// that will be returned from cache Get for k, v and mask. The capacity of the
+	// cache itself will also be increased to a multiple of this size if needed.
+	CachePadding int
+
+	// PermutedV performs Permute(ctx, 1, 2, 0, 3) on v tensors stored via Put
+	// and return the permuted version via Get. This uses the cache copy operation
+	// to avoid a Contiguous call on the permuted tensor.
+	PermutedV bool
+
+	// MaskDType specifies the data type for generating the mask. If unset it will
+	// default to DTypeF32.
+	MaskDType DType
+
+	// MaskBatchPadding specifies the multiple for the batch size dimension in the mask.
+	// Any position that does not correspond to an actual token will be filled with -Inf.
+	MaskBatchPadding int
+}
+
 // BackendParams controls how the backend loads and executes models
 type BackendParams struct {
 	// NumThreads sets the number of threads to use if running on the CPU
@@ -40,6 +69,9 @@ type BackendParams struct {

 	// TensorSplit is the fraction of the model to offload to each GPU
 	TensorSplit []float32
+
+	// FlashAttention indicates that we should use a fused flash attention kernel
+	FlashAttention bool
 }

 var backends = make(map[string]func(*os.File, BackendParams) (Backend, error))
@@ -61,6 +93,7 @@ func NewBackend(f *os.File, params BackendParams) (Backend, error) {
 }

 type Context interface {
+	Empty(dtype DType, shape ...int) Tensor
 	Zeros(dtype DType, shape ...int) Tensor
 	FromFloatSlice(s []float32, shape ...int) (Tensor, error)
 	FromIntSlice(s []int32, shape ...int) (Tensor, error)
@@ -116,6 +149,10 @@ type Tensor interface {
 // operation equivalent to following code on a tensor named
 // query:
 //
+// query = query.Permute(ctx, 0, 2, 1, 3)
+// key = key.Permute(ctx, 0, 2, 1, 3)
+// value = value.Permute(ctx, 1, 2, 0, 3).Contiguous(ctx)
+//
 // kq := key.MulmatFullPrec(ctx, query)
 //
 // kq = kq.Scale(ctx, scale)
@@ -170,7 +207,7 @@ func Dump(ctx Context, t Tensor, opts ...DumpOptions) string {
 			return strconv.FormatFloat(float64(f), 'f', opts[0].Precision, 32)
 		})
 	case DTypeF16:
-		f32 := ctx.Zeros(DTypeF32, t.Shape()...)
+		f32 := ctx.Empty(DTypeF32, t.Shape()...)
 		f32 = t.Copy(ctx, f32)
 		return dump[[]float32](ctx, f32, opts[0].Items, func(f float32) string {
 			return strconv.FormatFloat(float64(f), 'f', opts[0].Precision, 32)
--- a/ml/backend/ggml/ggml.go
+++ b/ml/backend/ggml/ggml.go
@@ -79,6 +79,8 @@ var devices = sync.OnceValue(func() []device {
 })

 type Backend struct {
+	flashAttention bool
+
 	meta       *fs.GGML
 	cpus, gpus []Context
 	tensors    map[string]*Context
@@ -192,9 +194,10 @@ func New(r *os.File, params ml.BackendParams) (ml.Backend, error) {
 	}

 	return &Backend{
-		meta: meta,
-		cpus: cpus,
-		gpus: gpus,
+		flashAttention: params.FlashAttention,
+		meta:           meta,
+		cpus:           cpus,
+		gpus:           gpus,
 		sched: C.ggml_backend_sched_new(
 			(*C.ggml_backend_t)(unsafe.Pointer(&backends[0])),
 			(*C.ggml_backend_buffer_type_t)(unsafe.Pointer(&bufts[0])),
@@ -219,7 +222,7 @@ func (b *Backend) Get(name string) ml.Tensor {

 	for _, c := range append(b.gpus, b.cpus...) {
 		if t := C.ggml_get_tensor(c.ctx, cname); t != nil {
-			return &Tensor{t: t}
+			return &Tensor{b: b, t: t}
 		}
 	}

@@ -247,6 +250,14 @@ func (b *Backend) NewContext() ml.Context {
 	}
 }

+func (b *Backend) CacheConfig() ml.CacheConfig {
+	if b.flashAttention {
+		return ml.CacheConfig{CachePadding: 256, MaskDType: ml.DTypeF16, MaskBatchPadding: C.GGML_KQ_MASK_PAD}
+	} else {
+		return ml.CacheConfig{CachePadding: 32, PermutedV: true}
+	}
+}
+
 type Context struct {
 	b       *Backend
 	ctx     *C.struct_ggml_context
@@ -300,7 +311,7 @@ func shapeToGGML(shape []int) *C.int64_t {
 	return &sh[0]
 }

-func (c Context) Zeros(dtype ml.DType, shape ...int) ml.Tensor {
+func newTensor(ctx Context, dtype ml.DType, zero bool, shape []int) ml.Tensor {
 	if len(shape) < 1 || len(shape) > 4 {
 		panic("unsupported number of dimensions")
 	}
@@ -314,19 +325,29 @@ func (c Context) Zeros(dtype ml.DType, shape ...int) ml.Tensor {
 	var t *C.struct_ggml_tensor
 	switch dtype {
 	case ml.DTypeF32:
-		t = C.ggml_new_tensor(c.ctx, C.GGML_TYPE_F32, C.int(len(shape)), shapeToGGML(shape))
+		t = C.ggml_new_tensor(ctx.ctx, C.GGML_TYPE_F32, C.int(len(shape)), shapeToGGML(shape))
 	case ml.DTypeF16:
-		t = C.ggml_new_tensor(c.ctx, C.GGML_TYPE_F16, C.int(len(shape)), shapeToGGML(shape))
+		t = C.ggml_new_tensor(ctx.ctx, C.GGML_TYPE_F16, C.int(len(shape)), shapeToGGML(shape))
 	case ml.DTypeI32:
-		t = C.ggml_new_tensor(c.ctx, C.GGML_TYPE_I32, C.int(len(shape)), shapeToGGML(shape))
+		t = C.ggml_new_tensor(ctx.ctx, C.GGML_TYPE_I32, C.int(len(shape)), shapeToGGML(shape))
 	default:
 		panic("unsupported dtype")
 	}

-	b := C.ggml_backend_alloc_buffer(c.backend, C.ggml_nbytes(t))
+	b := C.ggml_backend_alloc_buffer(ctx.backend, C.ggml_nbytes(t))
 	C.ggml_backend_tensor_alloc(b, t, C.ggml_backend_buffer_get_base(b))
-	C.ggml_set_zero(t)
-	return &Tensor{t: t}
+	if zero {
+		C.ggml_set_zero(t)
+	}
+	return &Tensor{b: ctx.b, t: t}
+}
+
+func (c Context) Empty(dtype ml.DType, shape ...int) ml.Tensor {
+	return newTensor(c, dtype, false, shape)
+}
+
+func (c Context) Zeros(dtype ml.DType, shape ...int) ml.Tensor {
+	return newTensor(c, dtype, true, shape)
 }

 func fromSlice[S ~[]E, E float32 | int32](ctx Context, s S, shape []int, dtype uint32) (ml.Tensor, error) {
@@ -335,7 +356,7 @@ func fromSlice[S ~[]E, E float32 | int32](ctx Context, s S, shape []int, dtype u
 	if n == 0 {
 		var shape C.int64_t = 0
 		t := C.ggml_new_tensor(ctx.ctx, dtype, 1, &shape)
-		return &Tensor{t: t}, nil
+		return &Tensor{b: ctx.b, t: t}, nil
 	}

 	for _, v := range shape {
@@ -350,7 +371,7 @@ func fromSlice[S ~[]E, E float32 | int32](ctx Context, s S, shape []int, dtype u
 	b := C.ggml_backend_alloc_buffer(ctx.backend, C.ggml_nbytes(t))
 	C.ggml_backend_tensor_alloc(b, t, C.ggml_backend_buffer_get_base(b))
 	C.ggml_backend_tensor_set(t, unsafe.Pointer(&s[0]), 0, C.ggml_nbytes(t))
-	return &Tensor{t: t}, nil
+	return &Tensor{b: ctx.b, t: t}, nil
 }

 func (c Context) FromFloatSlice(s []float32, shape ...int) (ml.Tensor, error) {
@@ -368,6 +389,7 @@ func (c *Context) Close() {
 }

 type Tensor struct {
+	b    *Backend
 	t    *C.struct_ggml_tensor
 	sync func()
 }
@@ -434,6 +456,7 @@ func (t *Tensor) DType() ml.DType {

 func (t *Tensor) Add(ctx ml.Context, t2 ml.Tensor) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_add(ctx.(*Context).ctx, t.t, t2.(*Tensor).t),
 	}
 }
@@ -448,24 +471,28 @@ func (t *Tensor) Stack(ctx ml.Context, dim int, s ...ml.Tensor) ml.Tensor {

 func (t *Tensor) Concat(ctx ml.Context, t2 ml.Tensor, dim int) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_concat(ctx.(*Context).ctx, t.t, t2.(*Tensor).t, C.int(dim)),
 	}
 }

 func (t *Tensor) Contiguous(ctx ml.Context) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_cont(ctx.(*Context).ctx, t.t),
 	}
 }

 func (t *Tensor) Mul(ctx ml.Context, t2 ml.Tensor) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_mul(ctx.(*Context).ctx, t.t, t2.(*Tensor).t),
 	}
 }

 func (t *Tensor) Mulmat(ctx ml.Context, t2 ml.Tensor) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_mul_mat(ctx.(*Context).ctx, t.t, t2.(*Tensor).t),
 	}
 }
@@ -475,12 +502,13 @@ func (t *Tensor) MulmatFullPrec(ctx ml.Context, t2 ml.Tensor) ml.Tensor {
 	C.ggml_mul_mat_set_prec(mul, C.GGML_PREC_F32)

 	return &Tensor{
+		b: t.b,
 		t: mul,
 	}
 }

 func (t *Tensor) LayerNorm(ctx ml.Context, w, b ml.Tensor, eps float32) ml.Tensor {
-	tt := (&Tensor{t: C.ggml_norm(ctx.(*Context).ctx, t.t, C.float(eps))}).Mul(ctx, w)
+	tt := (&Tensor{b: t.b, t: C.ggml_norm(ctx.(*Context).ctx, t.t, C.float(eps))}).Mul(ctx, w)
 	if b != nil {
 		tt = tt.Add(ctx, b)
 	}
@@ -489,7 +517,7 @@ func (t *Tensor) LayerNorm(ctx ml.Context, w, b ml.Tensor, eps float32) ml.Tenso
 }

 func (t *Tensor) RMSNorm(ctx ml.Context, w ml.Tensor, eps float32) ml.Tensor {
-	return (&Tensor{t: C.ggml_rms_norm(ctx.(*Context).ctx, t.t, C.float(eps))}).Mul(ctx, w)
+	return (&Tensor{b: t.b, t: C.ggml_rms_norm(ctx.(*Context).ctx, t.t, C.float(eps))}).Mul(ctx, w)
 }

 func (t *Tensor) Pad(ctx ml.Context, shape ...int) ml.Tensor {
@@ -498,6 +526,7 @@ func (t *Tensor) Pad(ctx ml.Context, shape ...int) ml.Tensor {
 	}

 	return &Tensor{
+		b: t.b,
 		t: C.ggml_pad(ctx.(*Context).ctx, t.t, C.int(shape[0]), C.int(shape[1]), C.int(shape[2]), C.int(shape[3])),
 	}
 }
@@ -508,18 +537,21 @@ func (t *Tensor) Permute(ctx ml.Context, shape ...int) ml.Tensor {
 	}

 	return &Tensor{
+		b: t.b,
 		t: C.ggml_permute(ctx.(*Context).ctx, t.t, C.int(shape[0]), C.int(shape[1]), C.int(shape[2]), C.int(shape[3])),
 	}
 }

 func (t *Tensor) Rows(ctx ml.Context, t2 ml.Tensor) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_get_rows(ctx.(*Context).ctx, t.t, t2.(*Tensor).t),
 	}
 }

 func (t *Tensor) Copy(ctx ml.Context, t2 ml.Tensor) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_cpy(ctx.(*Context).ctx, t.t, t2.(*Tensor).t),
 	}
 }
@@ -528,18 +560,22 @@ func (t *Tensor) Reshape(ctx ml.Context, shape ...int) ml.Tensor {
 	switch len(shape) {
 	case 1:
 		return &Tensor{
+			b: t.b,
 			t: C.ggml_reshape_1d(ctx.(*Context).ctx, t.t, C.int64_t(shape[0])),
 		}
 	case 2:
 		return &Tensor{
+			b: t.b,
 			t: C.ggml_reshape_2d(ctx.(*Context).ctx, t.t, C.int64_t(shape[0]), C.int64_t(shape[1])),
 		}
 	case 3:
 		return &Tensor{
+			b: t.b,
 			t: C.ggml_reshape_3d(ctx.(*Context).ctx, t.t, C.int64_t(shape[0]), C.int64_t(shape[1]), C.int64_t(shape[2])),
 		}
 	case 4:
 		return &Tensor{
+			b: t.b,
 			t: C.ggml_reshape_4d(ctx.(*Context).ctx, t.t, C.int64_t(shape[0]), C.int64_t(shape[1]), C.int64_t(shape[2]), C.int64_t(shape[3])),
 		}
 	default:
@@ -549,18 +585,21 @@ func (t *Tensor) Reshape(ctx ml.Context, shape ...int) ml.Tensor {

 func (t *Tensor) Scale(ctx ml.Context, s float64) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_scale(ctx.(*Context).ctx, t.t, (C.float)(s)),
 	}
 }

 func (t *Tensor) Softmax(ctx ml.Context) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_soft_max(ctx.(*Context).ctx, t.t),
 	}
 }

 func (t *Tensor) Tanh(ctx ml.Context) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_tanh_inplace(ctx.(*Context).ctx, t.t),
 	}
 }
@@ -571,6 +610,7 @@ func (t *Tensor) Unpad(ctx ml.Context, shape ...int) ml.Tensor {
 	}

 	return &Tensor{
+		b: t.b,
 		t: C.ggml_unpad(ctx.(*Context).ctx, t.t, C.int(shape[0]), C.int(shape[1]), C.int(shape[2]), C.int(shape[3])),
 	}
 }
@@ -579,10 +619,12 @@ func (t *Tensor) View(ctx ml.Context, offset int, shape ...int) ml.Tensor {
 	switch len(shape) {
 	case 1:
 		return &Tensor{
+			b: t.b,
 			t: C.ggml_view_1d(ctx.(*Context).ctx, t.t, C.int64_t(shape[0]), C.size_t(offset)),
 		}
 	case 3:
 		return &Tensor{
+			b: t.b,
 			t: C.ggml_view_2d(ctx.(*Context).ctx, t.t,
 				C.int64_t(shape[0]), C.int64_t(shape[2]),
 				C.size_t(shape[1]),
@@ -590,6 +632,7 @@ func (t *Tensor) View(ctx ml.Context, offset int, shape ...int) ml.Tensor {
 		}
 	case 5:
 		return &Tensor{
+			b: t.b,
 			t: C.ggml_view_3d(ctx.(*Context).ctx, t.t,
 				C.int64_t(shape[0]), C.int64_t(shape[2]), C.int64_t(shape[4]),
 				C.size_t(shape[1]), C.size_t(shape[3]),
@@ -597,6 +640,7 @@ func (t *Tensor) View(ctx ml.Context, offset int, shape ...int) ml.Tensor {
 		}
 	case 7:
 		return &Tensor{
+			b: t.b,
 			t: C.ggml_view_4d(ctx.(*Context).ctx, t.t,
 				C.int64_t(shape[0]), C.int64_t(shape[2]), C.int64_t(shape[4]), C.int64_t(shape[6]),
 				C.size_t(shape[1]), C.size_t(shape[3]), C.size_t(shape[5]),
@@ -613,7 +657,7 @@ const (

 func (t *Tensor) RoPE(ctx ml.Context, positionIDs, ropeFactors ml.Tensor, ropeDim uint32, ropeBase, ropeScale float32) ml.Tensor {
 	if ropeFactors == nil {
-		ropeFactors = &Tensor{}
+		ropeFactors = &Tensor{b: t.b}
 	}

 	dequant := t.t
@@ -622,6 +666,7 @@ func (t *Tensor) RoPE(ctx ml.Context, positionIDs, ropeFactors ml.Tensor, ropeDi
 	}

 	return &Tensor{
+		b: t.b,
 		t: C.ggml_rope_ext(
 			ctx.(*Context).ctx, dequant, positionIDs.(*Tensor).t, ropeFactors.(*Tensor).t,
 			C.int(ropeDim),
@@ -639,18 +684,21 @@ func (t *Tensor) RoPE(ctx ml.Context, positionIDs, ropeFactors ml.Tensor, ropeDi

 func (t *Tensor) GELU(ctx ml.Context) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_gelu_inplace(ctx.(*Context).ctx, t.t),
 	}
 }

 func (t *Tensor) SILU(ctx ml.Context) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_silu_inplace(ctx.(*Context).ctx, t.t),
 	}
 }

 func (t *Tensor) Conv2D(ctx ml.Context, t2 ml.Tensor, s0, s1, p0, p1, d0, d1 int) ml.Tensor {
 	return &Tensor{
+		b: t.b,
 		t: C.ggml_conv_2d(ctx.(*Context).ctx, t.t, t2.(*Tensor).t, C.int(s0), C.int(s1), C.int(p0), C.int(p1), C.int(d0), C.int(d1)),
 	}
 }
@@ -661,13 +709,25 @@ func (t *Tensor) ScaledDotProductAttention(ctx ml.Context, key, value, mask ml.T
 		kqMask = mask.(*Tensor).t
 	}

-	kq := key.MulmatFullPrec(ctx, t)
-	kq = &Tensor{
-		t: C.ggml_soft_max_ext(ctx.(*Context).ctx, kq.(*Tensor).t, kqMask, C.float(scale), 0),
-	}
+	query := t.Permute(ctx, 0, 2, 1, 3)
+	key = key.Permute(ctx, 0, 2, 1, 3)

-	kqv := value.Mulmat(ctx, kq)
-	return kqv.Permute(ctx, 0, 2, 1, 3).Contiguous(ctx)
+	if t.b.flashAttention {
+		value = value.Permute(ctx, 0, 2, 1, 3)
+
+		kqv := C.ggml_flash_attn_ext(ctx.(*Context).ctx, query.(*Tensor).t, key.(*Tensor).t, value.(*Tensor).t, kqMask, C.float(scale), 0, 0)
+		C.ggml_flash_attn_ext_set_prec(kqv, C.GGML_PREC_F32)
+		return &Tensor{b: t.b, t: kqv}
+	} else {
+		kq := key.MulmatFullPrec(ctx, query)
+		kq = &Tensor{
+			b: t.b,
+			t: C.ggml_soft_max_ext(ctx.(*Context).ctx, kq.(*Tensor).t, kqMask, C.float(scale), 0),
+		}
+
+		kqv := value.Mulmat(ctx, kq)
+		return kqv.Permute(ctx, 0, 2, 1, 3).Contiguous(ctx)
+	}
 }

 func (b *Backend) SystemInfo() string {
--- a/ml/nn/attention.go
+++ b/ml/nn/attention.go
@@ -3,6 +3,7 @@ package nn
 import (
 	"fmt"

+	"github.com/ollama/ollama/kvcache"
 	"github.com/ollama/ollama/ml"
 )

@@ -11,40 +12,50 @@ import (
 //
 // Parameters:
 //   - ctx: Context for tensor operations
-//   - query: Query tensor (Q) with shape [d_k, seq_len_q, heads]
-//   - key: Key tensor (K) with shape [d_k, seq_len_k, kv_heads]
-//   - value: Value tensor (V) with shape [seq_len_k, d_v, kv_heads]
-//   - mask: Optional attention mask that is added to the attention score. If
-//     provided, should broadcast to [seq_len_k, seq_len_q, heads]
+//   - query: Query tensor (Q) with shape [d_k, heads, seq_len_q]
+//   - key: Key tensor (K) with shape [d_k, kv_heads, seq_len_k], can be nil to read from cache only
+//   - value: Value tensor (V) with shape [d_v, kv_heads, seq_len_k], can be nil to read from cache only
 //   - scale: Scaling factor, typically 1/√d_k where d_k is the key dimension
+//   - cache: KV cache to store key/value and get past history, can be nil to only use provided key/value
 //
 // Returns:
 //
 //	Attention output with shape [d_v, heads, seq_len_q]
-func Attention(ctx ml.Context, query, key, value, mask ml.Tensor, scale float64) ml.Tensor {
-	if query.Dim(0) != key.Dim(0) {
-		panic(fmt.Errorf("d_k in attention operation does not match between query(%v) and key(%v)", query.Dim(0), key.Dim(0)))
+func Attention(ctx ml.Context, query, key, value ml.Tensor, scale float64, cache kvcache.Cache) ml.Tensor {
+	if key != nil && value != nil {
+		if query.Dim(0) != key.Dim(0) {
+			panic(fmt.Errorf("d_k in attention operation does not match between query(%v) and key(%v)", query.Dim(0), key.Dim(0)))
+		}
+
+		if key.Dim(1) != value.Dim(1) {
+			panic(fmt.Errorf("kv_heads in attention operation does not match between key(%v) and value(%v)", key.Dim(1), value.Dim(1)))
+		}
+
+		if key.Dim(2) != value.Dim(2) {
+			panic(fmt.Errorf("seq_len_k in attention operation does not match between key(%v) and value(%v)", key.Dim(2), value.Dim(2)))
+		}
+
+		if cache != nil {
+			cache.Put(ctx, key, value)
+		}
+	} else if cache == nil {
+		panic("key & value tensors must be provided if cache is nil")
 	}

-	if mask != nil && query.Dim(1) != mask.Dim(1) {
-		panic(fmt.Errorf("seq_len_q in attention operation does not match between query(%v) and mask(%v)", query.Dim(1), mask.Dim(1)))
+	var mask ml.Tensor
+	if cache != nil {
+		key, value, mask = cache.Get(ctx)
 	}

-	if key.Dim(1) != value.Dim(0) {
-		panic(fmt.Errorf("seq_len_k in attention operation does not match between key(%v) and value(%v)", key.Dim(1), value.Dim(0)))
-	}
-
-	if mask != nil && key.Dim(1) != mask.Dim(0) {
-		panic(fmt.Errorf("seq_len_k in attention operation does not match between key(%v) and mask(%v)", key.Dim(1), mask.Dim(0)))
-	}
-
-	if key.Dim(2) != value.Dim(2) {
-		panic(fmt.Errorf("kv_heads in attention operation does not match between key(%v) and value(%v)", key.Dim(2), value.Dim(2)))
-	}
-
-	if sdpa, ok := query.(ml.ScaledDotProductAttention); ok {
+	// Only use the fast SDPA implementation if we have a cache, since that's what
+	// will do any expected backend-specific transformations for us
+	if sdpa, ok := query.(ml.ScaledDotProductAttention); ok && cache != nil {
 		return sdpa.ScaledDotProductAttention(ctx, key, value, mask, scale)
 	} else {
+		query = query.Permute(ctx, 0, 2, 1, 3)
+		key = key.Permute(ctx, 0, 2, 1, 3)
+		value = value.Permute(ctx, 1, 2, 0, 3).Contiguous(ctx)
+
 		kq := key.MulmatFullPrec(ctx, query)

 		kq = kq.Scale(ctx, scale)
--- a/model/models/llama/model.go
+++ b/model/models/llama/model.go
@@ -81,15 +81,8 @@ func (sa *SelfAttention) Forward(ctx ml.Context, hiddenState, positionIDs ml.Ten
 	v := sa.Value.Forward(ctx, hiddenState)
 	v = v.Reshape(ctx, headDim, opts.numKVHeads, batchSize)

-	cache.Put(ctx, k, v)
-	k, v, mask := cache.Get(ctx)
-
-	q = q.Permute(ctx, 0, 2, 1, 3).Contiguous(ctx)
-	k = k.Permute(ctx, 0, 2, 1, 3).Contiguous(ctx)
-	v = v.Permute(ctx, 1, 2, 0, 3).Contiguous(ctx)
-
 	scaleFactor := 1.0 / math.Sqrt(float64(headDim))
-	kqv := nn.Attention(ctx, q, k, v, mask, scaleFactor)
+	kqv := nn.Attention(ctx, q, k, v, scaleFactor, cache)
 	kqv = kqv.Reshape(ctx, opts.hiddenSize, batchSize)

 	return sa.Output.Forward(ctx, kqv)
--- a/model/models/mllama/model.go
+++ b/model/models/mllama/model.go
@@ -43,7 +43,9 @@ func New(c ml.Config) (model.Model, error) {
 		TextModel:      newTextModel(c),
 	}

-	m.Cache = kvcache.NewWrapperCache(kvcache.NewEncoderCache(), kvcache.NewCausalCache(m.TextModel.Shift))
+	encoderCache := kvcache.NewEncoderCache()
+	encoderCache.SetConfig(ml.CacheConfig{})
+	m.Cache = kvcache.NewWrapperCache(encoderCache, kvcache.NewCausalCache(m.TextModel.Shift))

 	return &m, nil
 }
--- a/model/models/mllama/model_text.go
+++ b/model/models/mllama/model_text.go
@@ -31,22 +31,15 @@ func (sa *TextSelfAttention) Forward(ctx ml.Context, hiddenState, positions, _ m
 	value := sa.Value.Forward(ctx, hiddenState)
 	value = value.Reshape(ctx, headDim, opts.numKVHeads, batchSize)

-	cache.Put(ctx, key, value)
-	key, value, mask := cache.Get(ctx)
-
-	query = query.Permute(ctx, 0, 2, 1, 3).Contiguous(ctx)
-	key = key.Permute(ctx, 0, 2, 1, 3).Contiguous(ctx)
-	value = value.Permute(ctx, 1, 2, 0, 3).Contiguous(ctx)
-
 	scaleFactor := 1.0 / math.Sqrt(float64(headDim))
-	attention := nn.Attention(ctx, query, key, value, mask, scaleFactor)
+	attention := nn.Attention(ctx, query, key, value, scaleFactor, cache)
 	attention = attention.Reshape(ctx, opts.hiddenSize, batchSize)

 	return sa.Output.Forward(ctx, attention)
 }

 func (m *TextModel) Shift(ctx ml.Context, layer int, key, shift ml.Tensor) (ml.Tensor, error) {
-	// This will only get called for layers in the cache, which are just the self attention layers
+	// This will only get called for layers in the causal cache, which are just the self attention layers
 	return key.RoPE(ctx, shift, m.RopeFactors, m.ropeDim, m.ropeBase, m.ropeScale), nil
 }

@@ -107,7 +100,7 @@ func (ca *TextCrossAttention) Forward(ctx ml.Context, hiddenState, crossAttentio
 	query = query.Reshape(ctx, headDim, opts.numHeads, batchSize)
 	query = ca.QueryNorm.Forward(ctx, query, opts.eps)

-	var key, value, mask ml.Tensor
+	var key, value ml.Tensor
 	if crossAttentionStates != nil {
 		numVisionTokens, numTiles := crossAttentionStates.Dim(1), crossAttentionStates.Dim(2)

@@ -119,16 +112,23 @@ func (ca *TextCrossAttention) Forward(ctx ml.Context, hiddenState, crossAttentio
 		value = value.Reshape(ctx, headDim, opts.numKVHeads, numVisionTokens*numTiles)

 		cache.Put(ctx, key, value)
-	} else {
-		key, value, mask = cache.Get(ctx)
 	}

-	query = query.Permute(ctx, 0, 2, 1, 3).Contiguous(ctx)
-	key = key.Permute(ctx, 0, 2, 1, 3).Contiguous(ctx)
-	value = value.Permute(ctx, 1, 2, 0, 3).Contiguous(ctx)
+	key, value, _ = cache.Get(ctx)

 	scaleFactor := 1.0 / math.Sqrt(float64(headDim))
-	attention := nn.Attention(ctx, query, key, value, mask, scaleFactor)
+
+	query = query.Permute(ctx, 0, 2, 1, 3)
+	key = key.Permute(ctx, 0, 2, 1, 3)
+	value = value.Permute(ctx, 1, 2, 0, 3).Contiguous(ctx)
+
+	kq := key.MulmatFullPrec(ctx, query)
+
+	kq = kq.Scale(ctx, scaleFactor)
+	kq = kq.Softmax(ctx)
+
+	kqv := value.Mulmat(ctx, kq)
+	attention := kqv.Permute(ctx, 0, 2, 1, 3).Contiguous(ctx)
 	attention = attention.Reshape(ctx, opts.hiddenSize, batchSize)

 	return ca.Output.Forward(ctx, attention)
--- a/runner/ollamarunner/runner.go
+++ b/runner/ollamarunner/runner.go
@@ -818,7 +818,7 @@ func Execute(args []string) error {
 	batchSize := fs.Int("batch-size", 512, "Batch size")
 	numGPULayers := fs.Int("n-gpu-layers", 0, "Number of layers to offload to GPU")
 	mainGPU := fs.Int("main-gpu", 0, "Main GPU")
-	_ = fs.Bool("flash-attn", false, "Enable flash attention")
+	flashAttention := fs.Bool("flash-attn", false, "Enable flash attention")
 	kvSize := fs.Int("ctx-size", 2048, "Context (or KV cache) size")
 	kvCacheType := fs.String("kv-cache-type", "", "quantization type for KV cache (default: f16)")
 	port := fs.Int("port", 8080, "Port to expose the server on")
@@ -863,7 +863,6 @@ func Execute(args []string) error {
 	}

 	// TODO(jessegross): Parameters that need to be implemented:
-	//	flash-attn
 	//	no-mmap
 	//	mlock

@@ -878,10 +877,11 @@ func Execute(args []string) error {
 	}

 	params := ml.BackendParams{
-		NumThreads:   *threads,
-		NumGPULayers: *numGPULayers,
-		MainGPU:      *mainGPU,
-		TensorSplit:  tensorSplitFloats,
+		NumThreads:     *threads,
+		NumGPULayers:   *numGPULayers,
+		MainGPU:        *mainGPU,
+		TensorSplit:    tensorSplitFloats,
+		FlashAttention: *flashAttention,
 	}

 	server.ready.Add(1)
--- a/server/internal/client/ollama/registry.go
+++ b/server/internal/client/ollama/registry.go
@@ -24,6 +24,7 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
+	"slices"
 	"strconv"
 	"strings"
 	"sync/atomic"
@@ -53,7 +54,7 @@ var (

 	// ErrMissingModel is returned when the model part of a name is missing
 	// or invalid.
-	ErrNameInvalid = errors.New("invalid name; must be in the form {scheme://}{host/}{namespace/}[model]{:tag}{@digest}")
+	ErrNameInvalid = errors.New("invalid or missing name")

 	// ErrCached is passed to [Trace.PushUpdate] when a layer already
 	// exists. It is a non-fatal error and is never returned by [Registry.Push].
@@ -205,10 +206,18 @@ type Registry struct {
 	// It is only used when a layer is larger than [MaxChunkingThreshold].
 	MaxChunkSize int64

-	// NameMask, if set, is the name used to convert non-fully qualified
+	// Mask, if set, is the name used to convert non-fully qualified
 	// names to fully qualified names. If empty, the default mask
 	// ("registry.ollama.ai/library/_:latest") is used.
-	NameMask string
+	Mask string
+}
+
+func (r *Registry) completeName(name string) names.Name {
+	mask := defaultMask
+	if r.Mask != "" {
+		mask = names.Parse(r.Mask)
+	}
+	return names.Merge(names.Parse(name), mask)
 }

 // DefaultRegistry returns a new Registry configured from the environment. The
@@ -243,52 +252,6 @@ func DefaultRegistry() (*Registry, error) {
 	return &rc, nil
 }

-type PushParams struct {
-	// From is an optional destination name for the model. If empty, the
-	// destination name is the same as the source name.
-	From string
-}
-
-// parseName parses name using [names.ParseExtended] and then merges the name with the
-// default name, and checks that the name is fully qualified. If a digest is
-// present, it parse and returns it with the other fields as their zero values.
-//
-// It returns an error if the name is not fully qualified, or if the digest, if
-// any, is invalid.
-//
-// The scheme is returned as provided by [names.ParseExtended].
-func parseName(s, mask string) (scheme string, n names.Name, d blob.Digest, err error) {
-	maskName := defaultMask
-	if mask != "" {
-		maskName = names.Parse(mask)
-		if !maskName.IsFullyQualified() {
-			return "", names.Name{}, blob.Digest{}, fmt.Errorf("invalid name mask: %s", mask)
-		}
-	}
-	scheme, n, ds := names.ParseExtended(s)
-	if !n.IsValid() {
-		return "", names.Name{}, blob.Digest{}, fmt.Errorf("%w: %q", ErrNameInvalid, s)
-	}
-	n = names.Merge(n, maskName)
-	if ds != "" {
-		// Digest is present. Validate it.
-		d, err = blob.ParseDigest(ds)
-		if err != nil {
-			return "", names.Name{}, blob.Digest{}, err
-		}
-	}
-
-	// The name check is deferred until after the digest check because we
-	// say that digests take precedence over names, and so should there
-	// errors when being parsed.
-	if !n.IsFullyQualified() {
-		return "", names.Name{}, blob.Digest{}, fmt.Errorf("%w: %q", ErrNameInvalid, s)
-	}
-
-	scheme = cmp.Or(scheme, "https")
-	return scheme, n, d, nil
-}
-
 func (r *Registry) maxStreams() int {
 	n := cmp.Or(r.MaxStreams, runtime.GOMAXPROCS(0))

@@ -308,6 +271,12 @@ func (r *Registry) maxChunkSize() int64 {
 	return cmp.Or(r.MaxChunkSize, DefaultMaxChunkSize)
 }

+type PushParams struct {
+	// From is an optional destination name for the model. If empty, the
+	// destination name is the same as the source name.
+	From string
+}
+
 // Push pushes the model with the name in the cache to the remote registry.
 func (r *Registry) Push(ctx context.Context, c *blob.DiskCache, name string, p *PushParams) error {
 	if p == nil {
@@ -337,7 +306,7 @@ func (r *Registry) Push(ctx context.Context, c *blob.DiskCache, name string, p *

 	t := traceFromContext(ctx)

-	scheme, n, _, err := parseName(name, r.NameMask)
+	scheme, n, _, err := parseName(name, r.Mask)
 	if err != nil {
 		// This should never happen since ResolveLocal should have
 		// already validated the name.
@@ -431,7 +400,7 @@ func canRetry(err error) bool {
 // typically slower than splitting the model up across layers, and is mostly
 // utilized for layers of type equal to "application/vnd.ollama.image".
 func (r *Registry) Pull(ctx context.Context, c *blob.DiskCache, name string) error {
-	scheme, n, _, err := parseName(name, r.NameMask)
+	scheme, n, _, err := parseName(name, r.Mask)
 	if err != nil {
 		return err
 	}
@@ -582,9 +551,9 @@ func (r *Registry) Pull(ctx context.Context, c *blob.DiskCache, name string) err
 // Unlink is like [blob.DiskCache.Unlink], but makes name fully qualified
 // before attempting to unlink the model.
 func (r *Registry) Unlink(c *blob.DiskCache, name string) (ok bool, _ error) {
-	_, n, _, err := parseName(name, r.NameMask)
-	if err != nil {
-		return false, err
+	n := r.completeName(name)
+	if !n.IsFullyQualified() {
+		return false, fmt.Errorf("%w: %q", ErrNameInvalid, name)
 	}
 	return c.Unlink(n.String())
 }
@@ -658,9 +627,9 @@ type Layer struct {
 }

 // ResolveLocal resolves a name to a Manifest in the local cache. The name is
-// parsed using [names.ParseExtended] but the scheme is ignored.
+// parsed using [names.Split] but the scheme is ignored.
 func (r *Registry) ResolveLocal(c *blob.DiskCache, name string) (*Manifest, error) {
-	_, n, d, err := parseName(name, r.NameMask)
+	_, n, d, err := parseName(name, r.Mask)
 	if err != nil {
 		return nil, err
 	}
@@ -686,7 +655,7 @@ func (r *Registry) ResolveLocal(c *blob.DiskCache, name string) (*Manifest, erro

 // Resolve resolves a name to a Manifest in the remote registry.
 func (r *Registry) Resolve(ctx context.Context, name string) (*Manifest, error) {
-	scheme, n, d, err := parseName(name, r.NameMask)
+	scheme, n, d, err := parseName(name, r.Mask)
 	if err != nil {
 		return nil, err
 	}
@@ -869,3 +838,69 @@ func maybeUnexpectedEOF(err error) error {
 	}
 	return err
 }
+
+type publicError struct {
+	wrapped error
+	message string
+}
+
+func withPublicMessagef(err error, message string, args ...any) error {
+	return publicError{wrapped: err, message: fmt.Sprintf(message, args...)}
+}
+
+func (e publicError) Error() string { return e.message }
+func (e publicError) Unwrap() error { return e.wrapped }
+
+var supportedSchemes = []string{
+	"http",
+	"https",
+	"https+insecure",
+}
+
+var supportedSchemesMessage = fmt.Sprintf("supported schemes are %v", strings.Join(supportedSchemes, ", "))
+
+// parseName parses and validates an extended name, returning the scheme, name,
+// and digest.
+//
+// If the scheme is empty, scheme will be "https". If an unsupported scheme is
+// given, [ErrNameInvalid] wrapped with a display friendly message is returned.
+//
+// If the digest is invalid, [ErrNameInvalid] wrapped with a display friendly
+// message is returned.
+//
+// If the name is not, once merged with the mask, fully qualified,
+// [ErrNameInvalid] wrapped with a display friendly message is returned.
+func parseName(s string, mask string) (scheme string, _ names.Name, _ blob.Digest, _ error) {
+	scheme, name, digest := names.Split(s)
+	scheme = cmp.Or(scheme, "https")
+	if !slices.Contains(supportedSchemes, scheme) {
+		err := withPublicMessagef(ErrNameInvalid, "unsupported scheme: %q: %s", scheme, supportedSchemesMessage)
+		return "", names.Name{}, blob.Digest{}, err
+	}
+
+	var d blob.Digest
+	if digest != "" {
+		var err error
+		d, err = blob.ParseDigest(digest)
+		if err != nil {
+			err = withPublicMessagef(ErrNameInvalid, "invalid digest: %q", digest)
+			return "", names.Name{}, blob.Digest{}, err
+		}
+		if name == "" {
+			// We have can resolve a manifest from a digest only,
+			// so skip name validation and return the scheme and
+			// digest.
+			return scheme, names.Name{}, d, nil
+		}
+	}
+
+	maskName := defaultMask
+	if mask != "" {
+		maskName = names.Parse(mask)
+	}
+	n := names.Merge(names.Parse(name), maskName)
+	if !n.IsFullyQualified() {
+		return "", names.Name{}, blob.Digest{}, fmt.Errorf("%w: %q", ErrNameInvalid, s)
+	}
+	return scheme, n, d, nil
+}
--- a/server/internal/client/ollama/registry_test.go
+++ b/server/internal/client/ollama/registry_test.go
@@ -84,14 +84,14 @@ func newClient(t *testing.T, h http.HandlerFunc) (*Registry, *blob.DiskCache) {
 		}
 	}

-	rc := &Registry{
+	r := &Registry{
 		HTTPClient: &http.Client{
 			Transport: recordRoundTripper(h),
 		},
 	}

 	link := func(name string, manifest string) {
-		_, n, _, err := parseName(name, rc.NameMask)
+		_, n, _, err := parseName(name, r.Mask)
 		if err != nil {
 			panic(err)
 		}
@@ -122,7 +122,7 @@ func newClient(t *testing.T, h http.HandlerFunc) (*Registry, *blob.DiskCache) {
 	commit("sizemismatch", mklayer("exists"), &Layer{Digest: blob.DigestFromBytes("present"), Size: 499})
 	link("invalid", "!!!!!")

-	return rc, c
+	return r, c
 }

 func okHandler(w http.ResponseWriter, r *http.Request) {
@@ -145,29 +145,6 @@ func importBytes(t *testing.T, c *blob.DiskCache, data string) blob.Digest {
 	return d
 }

-func TestRegistryPushInvalidNames(t *testing.T) {
-	rc, c := newClient(t, nil)
-
-	cases := []struct {
-		name string
-		err  error
-	}{
-		{"", ErrNameInvalid},
-		{"@", ErrNameInvalid},
-		{"@x", blob.ErrInvalidDigest},
-	}
-
-	for _, tt := range cases {
-		t.Run(tt.name, func(t *testing.T) {
-			// Create a new registry and push a new image.
-			err := rc.Push(t.Context(), c, tt.name, nil)
-			if !errors.Is(err, tt.err) {
-				t.Errorf("err = %v; want %v", err, tt.err)
-			}
-		})
-	}
-}
-
 func withTraceUnexpected(ctx context.Context) (context.Context, *Trace) {
 	t := &Trace{Update: func(*Layer, int64, error) { panic("unexpected") }}
 	return WithTrace(ctx, t), t
@@ -622,7 +599,7 @@ func TestInsecureSkipVerify(t *testing.T) {
 	}))
 	defer s.Close()

-	const name = "ollama.com/library/insecure"
+	const name = "library/insecure"

 	var rc Registry
 	url := fmt.Sprintf("https://%s/%s", s.Listener.Addr(), name)
@@ -724,3 +701,38 @@ func TestErrorUnmarshal(t *testing.T) {
 		})
 	}
 }
+
+// TestParseNameErrors tests that parseName returns errors messages with enough
+// detail for users to debug naming issues they may encounter. Previous to this
+// test, the error messages were not very helpful and each problem was reported
+// as the same message.
+//
+// It is only for testing error messages, not that all invalids and valids are
+// covered. Those are in other tests for names.Name and blob.Digest.
+func TestParseNameErrors(t *testing.T) {
+	cases := []struct {
+		name string
+		err  error
+		want string
+	}{
+		{"x", nil, ""},
+		{"x@", nil, ""},
+
+		{"", ErrNameInvalid, `invalid or missing name: ""`},
+		{"://", ErrNameInvalid, `invalid or missing name: "://"`},
+		{"x://", ErrNameInvalid, `unsupported scheme: "x": supported schemes are http, https, https+insecure`},
+
+		{"@sha123-1234", ErrNameInvalid, `invalid digest: "sha123-1234"`},
+		{"x@sha123-1234", ErrNameInvalid, `invalid digest: "sha123-1234"`},
+	}
+
+	for _, tt := range cases {
+		_, _, _, err := parseName(tt.name, DefaultMask)
+		if !errors.Is(err, tt.err) {
+			t.Errorf("[%s]: err = %v; want %v", tt.name, err, tt.err)
+		}
+		if err != nil && !strings.Contains(err.Error(), tt.want) {
+			t.Errorf("[%s]: err =\n\t%v\nwant\n\t%v", tt.name, err, tt.want)
+		}
+	}
+}
--- a/server/internal/internal/names/name.go
+++ b/server/internal/internal/names/name.go
@@ -8,7 +8,7 @@ import (
 	"github.com/ollama/ollama/server/internal/internal/stringsx"
 )

-const MaxNameLength = 50 + 1 + 50 + 1 + 50 // <namespace>/<model>:<tag>
+const MaxNameLength = 350 + 1 + 80 + 1 + 80 + 1 + 80 // <host>/<namespace>/<model>:<tag>

 type Name struct {
 	// Make incomparable to enfoce use of Compare / Equal for
@@ -25,19 +25,12 @@ type Name struct {
 // format of a valid name string is:
 //
 //	  s:
-//		  { host } "/" { namespace } "/" { model } ":" { tag } "@" { digest }
 //		  { host } "/" { namespace } "/" { model } ":" { tag }
-//		  { host } "/" { namespace } "/" { model } "@" { digest }
 //		  { host } "/" { namespace } "/" { model }
-//		  { namespace } "/" { model } ":" { tag } "@" { digest }
 //		  { namespace } "/" { model } ":" { tag }
-//		  { namespace } "/" { model } "@" { digest }
 //		  { namespace } "/" { model }
-//		  { model } ":" { tag } "@" { digest }
 //		  { model } ":" { tag }
-//		  { model } "@" { digest }
 //		  { model }
-//		  "@" { digest }
 //	  host:
 //	      pattern: { alphanum | "_" } { alphanum | "_" | "-" | "." | ":" }*
 //	      length:  [1, 350]
@@ -50,9 +43,6 @@ type Name struct {
 //	  tag:
 //	      pattern: { alphanum | "_" } { alphanum | "-" | "_" | "." }*
 //	      length:  [1, 80]
-//	  digest:
-//	      pattern: { alphanum | "_" } { alphanum | "-" | ":" }*
-//	      length:  [1, 80]
 //
 // The name returned is not guaranteed to be valid. If it is not valid, the
 // field values are left in an undefined state. Use [Name.IsValid] to check
@@ -82,23 +72,17 @@ func Parse(s string) Name {
 	}
 }

-// ParseExtended parses and returns any scheme, Name, and digest from from s in
-// the the form [scheme://][name][@digest]. All parts are optional.
-//
-// If the scheme is present, it must be followed by "://". The digest is
-// prefixed by "@" and comes after the name. The name is parsed using [Parse].
-//
-// The scheme and digest are stripped before the name is parsed by [Parse].
-//
-// For convience, the scheme is never empty. If the scheme is not present, the
-// returned scheme is "https".
+// Split splits an extended name string into its scheme, name, and digest
+// parts.
 //
 // Examples:
 //
 //	http://ollama.com/bmizerany/smol:latest@digest
 //	https://ollama.com/bmizerany/smol:latest
 //	ollama.com/bmizerany/smol:latest@digest // returns "https" scheme.
-func ParseExtended(s string) (scheme string, _ Name, digest string) {
+//	model@digest
+//	@digest
+func Split(s string) (scheme, name, digest string) {
 	i := strings.Index(s, "://")
 	if i >= 0 {
 		scheme = s[:i]
@@ -109,21 +93,7 @@ func ParseExtended(s string) (scheme string, _ Name, digest string) {
 		digest = s[i+1:]
 		s = s[:i]
 	}
-	return scheme, Parse(s), digest
-}
-
-func FormatExtended(scheme string, n Name, digest string) string {
-	var b strings.Builder
-	if scheme != "" {
-		b.WriteString(scheme)
-		b.WriteString("://")
-	}
-	b.WriteString(n.String())
-	if digest != "" {
-		b.WriteByte('@')
-		b.WriteString(digest)
-	}
-	return b.String()
+	return scheme, s, digest
 }

 // Merge merges two names into a single name. Non-empty host, namespace, and
@@ -141,39 +111,68 @@ func Merge(a, b Name) Name {

 // IsValid returns true if the name is valid.
 func (n Name) IsValid() bool {
-	if n.h != "" && !isValidHost(n.h) {
+	if n.h != "" && !isValidPart(partHost, n.h) {
 		return false
 	}
-	if n.n != "" && !isValidNamespace(n.n) {
+	if n.n != "" && !isValidPart(partNamespace, n.n) {
 		return false
 	}
-	if n.m != "" && !isValidModel(n.m) {
+	if n.t != "" && !isValidPart(partTag, n.t) {
 		return false
 	}
-	if n.t != "" && !isValidTag(n.t) {
-		return false
-	}
-	return true
+
+	// at bare minimum, model must be present and valid
+	return n.m != "" && isValidPart(partModel, n.m)
 }

 func (n Name) IsFullyQualified() bool {
 	return n.IsValid() && n.h != "" && n.n != "" && n.m != "" && n.t != ""
 }

-func isValidHost(_ string) bool {
-	return true // TODO: implement
+const (
+	partHost = iota
+	partNamespace
+	partModel
+	partTag
+)
+
+func isValidPart(kind int, s string) bool {
+	maxlen := 80
+	if kind == partHost {
+		maxlen = 350
+	}
+	if len(s) > maxlen {
+		return false
+	}
+
+	for i := range s {
+		if i == 0 {
+			if !isAlphanumericOrUnderscore(s[i]) {
+				return false
+			}
+			continue
+		}
+		switch s[i] {
+		case '_', '-':
+		case '.':
+			if kind == partNamespace {
+				return false
+			}
+		case ':':
+			if kind != partHost {
+				return false
+			}
+		default:
+			if !isAlphanumericOrUnderscore(s[i]) {
+				return false
+			}
+		}
+	}
+	return true
 }

-func isValidNamespace(_ string) bool {
-	return true // TODO: implement
-}
-
-func isValidModel(_ string) bool {
-	return true // TODO: implement
-}
-
-func isValidTag(_ string) bool {
-	return true // TODO: implement
+func isAlphanumericOrUnderscore(c byte) bool {
+	return c >= 'A' && c <= 'Z' || c >= 'a' && c <= 'z' || c >= '0' && c <= '9' || c == '_'
 }

 func (n Name) Host() string      { return n.h }
--- a/server/internal/internal/names/name_test.go
+++ b/server/internal/internal/names/name_test.go
@@ -81,15 +81,11 @@ func TestParseExtended(t *testing.T) {
 	}
 	for _, tt := range cases {
 		t.Run(tt.in, func(t *testing.T) {
-			scheme, name, digest := ParseExtended(tt.in)
-			if scheme != tt.wantScheme || name.Compare(tt.wantName) != 0 || digest != tt.wantDigest {
+			scheme, name, digest := Split(tt.in)
+			n := Parse(name)
+			if scheme != tt.wantScheme || n.Compare(tt.wantName) != 0 || digest != tt.wantDigest {
 				t.Errorf("ParseExtended(%q) = %q, %#v, %q, want %q, %#v, %q", tt.in, scheme, name, digest, tt.wantScheme, tt.wantName, tt.wantDigest)
 			}
-
-			// Round trip
-			if got := FormatExtended(scheme, name, digest); got != tt.in {
-				t.Errorf("FormatExtended(%q, %q, %q) = %q", scheme, name, digest, got)
-			}
 		})
 	}
 }
@@ -150,3 +146,75 @@ func BenchmarkParseName(b *testing.B) {
 		junkName = Parse("h/n/m:t")
 	}
 }
+
+const (
+	part80  = "88888888888888888888888888888888888888888888888888888888888888888888888888888888"
+	part350 = "33333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333"
+)
+
+var testCases = map[string]bool{ // name -> valid
+	"": false,
+
+	"_why/_the/_lucky:_stiff": true,
+
+	// minimal
+	"h/n/m:t": true,
+
+	"host/namespace/model:tag": true,
+	"host/namespace/model":     true,
+	"namespace/model":          true,
+	"model":                    true,
+
+	// long (but valid)
+	part80 + "/" + part80 + "/" + part80 + ":" + part80:  true,
+	part350 + "/" + part80 + "/" + part80 + ":" + part80: true,
+
+	// too long
+	part80 + "/" + part80 + "/" + part80 + ":" + part350:       false,
+	"x" + part350 + "/" + part80 + "/" + part80 + ":" + part80: false,
+
+	"h/nn/mm:t": true, // bare minimum part sizes
+
+	// unqualified
+	"m":     true,
+	"n/m:":  true,
+	"h/n/m": true,
+	"@t":    false,
+	"m@d":   false,
+
+	// invalids
+	"^":      false,
+	"mm:":    true,
+	"/nn/mm": true,
+	"//":     false, // empty model
+	"//mm":   true,
+	"hh//":   false, // empty model
+	"//mm:@": false,
+	"00@":    false,
+	"@":      false,
+
+	// not starting with alphanum
+	"-hh/nn/mm:tt": false,
+	"hh/-nn/mm:tt": false,
+	"hh/nn/-mm:tt": false,
+	"hh/nn/mm:-tt": false,
+
+	// smells like a flag
+	"-h": false,
+
+	// hosts
+	"host:https/namespace/model:tag": true,
+
+	// colon in non-host part before tag
+	"host/name:space/model:tag": false,
+}
+
+func TestParseNameValidation(t *testing.T) {
+	for s, valid := range testCases {
+		got := Parse(s)
+		if got.IsValid() != valid {
+			t.Logf("got: %v", got)
+			t.Errorf("Parse(%q).IsValid() = %v; want !%[2]v", s, got.IsValid())
+		}
+	}
+}
--- a/server/internal/registry/server.go
+++ b/server/internal/registry/server.go
@@ -204,7 +204,7 @@ func (s *Local) handleDelete(_ http.ResponseWriter, r *http.Request) error {
 		return err
 	}
 	if !ok {
-		return &serverError{404, "manifest_not_found", "manifest not found"}
+		return &serverError{404, "not_found", "model not found"}
 	}
 	return nil
 }
--- a/server/internal/registry/server_test.go
+++ b/server/internal/registry/server_test.go
@@ -109,11 +109,8 @@ func TestServerDelete(t *testing.T) {
 	got = s.send(t, "DELETE", "/api/delete", ``)
 	checkErrorResponse(t, got, 400, "bad_request", "empty request body")

-	got = s.send(t, "DELETE", "/api/delete", `{"model": "!"}`)
-	checkErrorResponse(t, got, 404, "manifest_not_found", "not found")
-
 	got = s.send(t, "DELETE", "/api/delete", `{"model": "://"}`)
-	checkErrorResponse(t, got, 400, "bad_request", "invalid name")
+	checkErrorResponse(t, got, 400, "bad_request", "invalid or missing name")

 	got = s.send(t, "DELETE", "/unknown_path", `{}`) // valid body
 	checkErrorResponse(t, got, 404, "not_found", "not found")