internal/llm: add ContentGenerator.SetTemperature

Add a method to ContentGenerator that allows changing the default
temperature.

Use it in labeleval to see if it reduces variability.

(It does, but it doesn't eliminate it.)

Change-Id: I85dd3ad16af1133627b48fd469ccdf7983f8aeea
Reviewed-on: https://go-review.googlesource.com/c/oscar/+/635284
Reviewed-by: Tatiana Bradley <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

internal/devtools/cmd/labeleval/main.go

@@ -261,8 +261,13 @@ Issues:
 
 func newGeminiClient(ctx context.Context, lg *slog.Logger) (*gemini.Client, error) {
 	sdb := secret.Netrc()
-	return gemini.NewClient(ctx, lg, sdb, http.DefaultClient,
+	c, err := gemini.NewClient(ctx, lg, sdb, http.DefaultClient,
 		gemini.DefaultEmbeddingModel, gemini.DefaultGenerativeModel)
+	if err != nil {
+		return nil, err
+	}
+	c.SetTemperature(0)
+	return c, nil
 }
 
 func readJSONFile(filename string, p any) error {

internal/gcp/gemini/gemini.go

@@ -53,6 +53,7 @@ type Client struct {
 	slog                            *slog.Logger
 	genai                           *genai.Client
 	embeddingModel, generativeModel string
+	temperature                     float32 // negative means use default
 }
 
 const (
@@ -89,7 +90,13 @@ func NewClient(ctx context.Context, lg *slog.Logger, sdb secret.DB, hc *http.Cli
 		return nil, err
 	}
 
-	return &Client{slog: lg, genai: ai, embeddingModel: embeddingModel, generativeModel: generativeModel}, nil
+	return &Client{
+		slog:            lg,
+		genai:           ai,
+		embeddingModel:  embeddingModel,
+		generativeModel: generativeModel,
+		temperature:     -1,
+	}, nil
 }
 
 // withKey returns a new http.Client that is the same as hc
@@ -150,6 +157,11 @@ func (c *Client) Model() string {
 	return c.generativeModel
 }
 
+// SetTemperature sets the temperature of the client's generative model.
+func (c *Client) SetTemperature(t float32) {
+	c.temperature = t
+}
+
 // GenerateContent returns the model's response for the prompt parts,
 // implementing [llm.ContentGenerator.GenerateContent].
 func (c *Client) GenerateContent(ctx context.Context, schema *llm.Schema, promptParts []llm.Part) (string, error) {
@@ -198,6 +210,9 @@ func (c *Client) model(mimeType string, schema *genai.Schema) *genai.GenerativeM
 	model.SetCandidateCount(1)
 	model.ResponseMIMEType = mimeType
 	model.ResponseSchema = schema
+	if c.temperature >= 0 {
+		model.SetTemperature(c.temperature)
+	}
 	return model
 }
 

internal/llm/llm.go

@@ -105,4 +105,6 @@ type ContentGenerator interface {
 	// and one or more prompt parts.
 	// If the JSON schema is nil, GenerateContent outputs a plain text response.
 	GenerateContent(ctx context.Context, schema *Schema, parts []Part) (string, error)
+	// SetTemperature changes the temperature of the model.
+	SetTemperature(float32)
 }

internal/llm/testing.go

@@ -96,6 +96,9 @@ type echo struct{}
 // Implements [ContentGenerator.Model].
 func (echo) Model() string { return "echo" }
 
+// Implements [ContentGenerator.SetTemperature] as a no-op.
+func (echo) SetTemperature(float32) {}
+
 // GenerateContent echoes the prompts.
 // If the schema is non-nil, the output is wrapped as a JSON object with a
 // single value "prompt", ignoring the actual schema contents (for testing).
@@ -159,6 +162,9 @@ func (g *generator) Model() string {
 	return g.model
 }
 
+// SetTemperature implements [ContentGenerator.SetTemperature] as a no-op.
+func (g *generator) SetTemperature(float32) {}
+
 // GenerateContent implements [ContentGenerator.GenerateContent].
 func (g *generator) GenerateContent(ctx context.Context, schema *Schema, promptParts []Part) (string, error) {
 	if g.generateContent == nil {