phi3 (#54)

* phi3

Co-authored-by: David Koski <dkoski@apple.com>

Libraries/LLM/Evaluate.swift

@@ -60,16 +60,16 @@ public struct GenerateParameters {
     public var temperature: Float = 0.6
 
     /// top p sampling
-    public var topP: Float = 0.9
+    public var topP: Float = 1.0
 
     /// penalty factor for repeating tokens
-    public var repetitionPenalty: Float = 1.0
+    public var repetitionPenalty: Float?
 
     /// number of tokens to consider for repetition penalty
     public var repetitionContextSize: Int = 20
 
     public init(
-        temperature: Float = 0.6, topP: Float = 0.9, repetitionPenalty: Float = 1.0,
+        temperature: Float = 0.6, topP: Float = 1.0, repetitionPenalty: Float? = nil,
         repetitionContextSize: Int = 20
     ) {
         self.temperature = temperature
@@ -111,11 +111,11 @@ public struct TokenIterator: Sequence, IteratorProtocol {
         var logits: MLXArray
         (logits, cache) = model(expandedDimensions(y, axis: 0), cache: cache.isEmpty ? nil : cache)
         logits = logits[0..., -1, 0...]
-        if parameters.repetitionPenalty > 1.0 {
+        if let repetitionPenalty = parameters.repetitionPenalty {
             // apply repetition penalty
             logits = applyRepetitionPenalty(
                 logits: logits, repetitionContext: repetitionContext,
-                penalty: parameters.repetitionPenalty)
+                penalty: repetitionPenalty)
         }
         y = sample(logits: logits, temp: parameters.temperature, topP: parameters.topP)
         // append the current token to the context and check repetitionPenalty context see if need to remove the first token