[LLM-CHAT] Enable gpu softmax for penality softmax (#2288)

1. Avoid the cpu softmax for different penality config by
  having copy sync to gpu and use gpu softmax.
2. Disable decode token time counter for first token.

cpp/llm_chat.cc

@@ -710,7 +710,7 @@ class LLMChat {
   /*! \brief reset the runtime stats. */
   void ResetRuntimeStats() {
     this->prefill_total_tokens = 0;
-    this->decode_total_tokens = 0;
+    this->decode_total_tokens = -1;
     this->embed_total_time = 0;
     this->prefill_total_time = 0;
     this->decode_total_time = 0;
@@ -1031,8 +1031,8 @@ class LLMChat {
     int32_t next_token = this->SampleTokenFromLogits(logits_on_device, generation_config);
 
     auto tend = std::chrono::high_resolution_clock::now();
-
-    this->decode_total_time += static_cast<double>((tend - tstart).count()) / 1e9;
+    if (this->decode_total_tokens >= 0)
+      this->decode_total_time += static_cast<double>((tend - tstart).count()) / 1e9;
     this->decode_total_tokens += 1;
     this->ProcessNextToken(next_token, generation_config);
   }
@@ -1223,14 +1223,16 @@ class LLMChat {
     if (gen_presence_penalty != 0.0f || gen_frequency_penalty != 0.0f) {
       this->UpdateLogitsOrProbOnCPUSync(logits_on_device);
       this->ApplyPresenceAndFrequencyPenaltyOnCPU(gen_presence_penalty, gen_frequency_penalty);
+      this->UpdateLogitsOrProbOnGPUSync(logits_on_device);
       if (gen_temperature >= 1e-6f) {
-        this->ApplySoftmaxWithTemperatureOnCPU(gen_temperature);
+        this->UpdateLogitsOrProbOnCPUSync(this->Softmax(logits_on_device, this->temperature_arr_));
       }
     } else if (gen_repetition_penalty != 1.0f) {
       this->UpdateLogitsOrProbOnCPUSync(logits_on_device);
       this->ApplyRepetitionPenaltyOnCPU(gen_repetition_penalty);
+      this->UpdateLogitsOrProbOnGPUSync(logits_on_device);
       if (gen_temperature >= 1e-6f) {
-        this->ApplySoftmaxWithTemperatureOnCPU(gen_temperature);
+        this->UpdateLogitsOrProbOnCPUSync(this->Softmax(logits_on_device, this->temperature_arr_));
       }
     } else {
       if (gen_temperature < 1e-6f) {
@@ -1505,6 +1507,12 @@ class LLMChat {
     TVMSynchronize(device_.device_type, device_.device_id, nullptr);
   }
 
+  void UpdateLogitsOrProbOnGPUSync(NDArray logits_or_prob) {
+    logits_or_prob.CopyFrom(logits_on_cpu_);
+
+    TVMSynchronize(device_.device_type, device_.device_id, nullptr);
+  }
+
   // Clear kv cache
   void ResetKVCache() {
     ft_.reset_kv_cache_func_(kv_cache_);
@@ -1547,7 +1555,7 @@ class LLMChat {
   double decode_total_time = 0;
   double sample_total_time = 0;
   double prefill_total_time = 0;
-  int64_t decode_total_tokens = 0;
+  int64_t decode_total_tokens = -1;
   int64_t prefill_total_tokens = 0;
   //----------------------------
   // Conversation