server: add logprobs and top_logprobs support to Ollama's API (#12899)

Adds logprobs support to Ollama's API including support for Ollama's
OpenAI-compatible API. By specifying the new 'logprobs' boolean parameter
in the API, Ollama will return the log probabilities for each token generated.
'top_logprobs', an integer value can also be specified up to the value 20.
When specified, the API will also provide the number of most likely tokens to
return at each token position

Co-authored-by: Baptiste Jamin <baptiste@crisp.chat>

openai/openai.go

@@ -40,22 +40,29 @@ type Message struct {
 	ToolCallID string     `json:"tool_call_id,omitempty"`
 }
 
+type ChoiceLogprobs struct {
+	Content []api.Logprob `json:"content"`
+}
+
 type Choice struct {
-	Index        int     `json:"index"`
-	Message      Message `json:"message"`
-	FinishReason *string `json:"finish_reason"`
+	Index        int             `json:"index"`
+	Message      Message         `json:"message"`
+	FinishReason *string         `json:"finish_reason"`
+	Logprobs     *ChoiceLogprobs `json:"logprobs,omitempty"`
 }
 
 type ChunkChoice struct {
-	Index        int     `json:"index"`
-	Delta        Message `json:"delta"`
-	FinishReason *string `json:"finish_reason"`
+	Index        int             `json:"index"`
+	Delta        Message         `json:"delta"`
+	FinishReason *string         `json:"finish_reason"`
+	Logprobs     *ChoiceLogprobs `json:"logprobs,omitempty"`
 }
 
 type CompleteChunkChoice struct {
-	Text         string  `json:"text"`
-	Index        int     `json:"index"`
-	FinishReason *string `json:"finish_reason"`
+	Text         string          `json:"text"`
+	Index        int             `json:"index"`
+	FinishReason *string         `json:"finish_reason"`
+	Logprobs     *ChoiceLogprobs `json:"logprobs,omitempty"`
 }
 
 type Usage struct {
@@ -104,6 +111,8 @@ type ChatCompletionRequest struct {
 	Tools            []api.Tool      `json:"tools"`
 	Reasoning        *Reasoning      `json:"reasoning,omitempty"`
 	ReasoningEffort  *string         `json:"reasoning_effort,omitempty"`
+	Logprobs         *bool           `json:"logprobs"`
+	TopLogprobs      int             `json:"top_logprobs"`
 	DebugRenderOnly  bool            `json:"_debug_render_only"`
 }
 
@@ -142,6 +151,7 @@ type CompletionRequest struct {
 	Temperature      *float32       `json:"temperature"`
 	TopP             float32        `json:"top_p"`
 	Suffix           string         `json:"suffix"`
+	Logprobs         *int           `json:"logprobs"`
 	DebugRenderOnly  bool           `json:"_debug_render_only"`
 }
 
@@ -251,6 +261,12 @@ func ToToolCalls(tc []api.ToolCall) []ToolCall {
 // ToChatCompletion converts an api.ChatResponse to ChatCompletion
 func ToChatCompletion(id string, r api.ChatResponse) ChatCompletion {
 	toolCalls := ToToolCalls(r.Message.ToolCalls)
+
+	var logprobs *ChoiceLogprobs
+	if len(r.Logprobs) > 0 {
+		logprobs = &ChoiceLogprobs{Content: r.Logprobs}
+	}
+
 	return ChatCompletion{
 		Id:                id,
 		Object:            "chat.completion",
@@ -269,6 +285,7 @@ func ToChatCompletion(id string, r api.ChatResponse) ChatCompletion {
 				}
 				return nil
 			}(r.DoneReason),
+			Logprobs: logprobs,
 		}}, Usage: ToUsage(r),
 		DebugInfo: r.DebugInfo,
 	}
@@ -277,6 +294,12 @@ func ToChatCompletion(id string, r api.ChatResponse) ChatCompletion {
 // ToChunk converts an api.ChatResponse to ChatCompletionChunk
 func ToChunk(id string, r api.ChatResponse, toolCallSent bool) ChatCompletionChunk {
 	toolCalls := ToToolCalls(r.Message.ToolCalls)
+
+	var logprobs *ChoiceLogprobs
+	if len(r.Logprobs) > 0 {
+		logprobs = &ChoiceLogprobs{Content: r.Logprobs}
+	}
+
 	return ChatCompletionChunk{
 		Id:                id,
 		Object:            "chat.completion.chunk",
@@ -295,6 +318,7 @@ func ToChunk(id string, r api.ChatResponse, toolCallSent bool) ChatCompletionChu
 				}
 				return nil
 			}(r.DoneReason),
+			Logprobs: logprobs,
 		}},
 	}
 }
@@ -604,6 +628,8 @@ func FromChatRequest(r ChatCompletionRequest) (*api.ChatRequest, error) {
 		Stream:          &r.Stream,
 		Tools:           r.Tools,
 		Think:           think,
+		Logprobs:        r.Logprobs != nil && *r.Logprobs,
+		TopLogprobs:     r.TopLogprobs,
 		DebugRenderOnly: r.DebugRenderOnly,
 	}, nil
 }
@@ -680,12 +706,21 @@ func FromCompleteRequest(r CompletionRequest) (api.GenerateRequest, error) {
 		options["top_p"] = 1.0
 	}
 
+	var logprobs bool
+	var topLogprobs int
+	if r.Logprobs != nil && *r.Logprobs > 0 {
+		logprobs = true
+		topLogprobs = *r.Logprobs
+	}
+
 	return api.GenerateRequest{
 		Model:           r.Model,
 		Prompt:          r.Prompt,
 		Options:         options,
 		Stream:          &r.Stream,
 		Suffix:          r.Suffix,
+		Logprobs:        logprobs,
+		TopLogprobs:     topLogprobs,
 		DebugRenderOnly: r.DebugRenderOnly,
 	}, nil
 }