server : add server parameters for draft model cache type (ggml-org#13782)

Co-authored-by: aa956 <27946957+aa956@users.noreply.github.com>

Author: aa956

common/common.h

@@ -199,6 +199,9 @@ struct common_params_speculative {
     float   p_split      =  0.1f; // speculative decoding split probability
     float   p_min        = 0.75f; // minimum speculative decoding probability (greedy)
 
+    ggml_type cache_type_k = GGML_TYPE_F16; // KV cache data type for the K
+    ggml_type cache_type_v = GGML_TYPE_F16; // KV cache data type for the V
+
     struct cpu_params cpuparams;
     struct cpu_params cpuparams_batch;
 

tools/server/server.cpp

@@ -1969,10 +1969,8 @@ struct server_context {
             params_dft.n_ctx        = params_base.speculative.n_ctx == 0 ? params_base.n_ctx / params_base.n_parallel : params_base.speculative.n_ctx;
             params_dft.n_gpu_layers = params_base.speculative.n_gpu_layers;
             params_dft.n_parallel   = 1;
-
-            // force F16 KV cache for the draft model for extra performance
-            params_dft.cache_type_k = GGML_TYPE_F16;
-            params_dft.cache_type_v = GGML_TYPE_F16;
+            params_dft.cache_type_k = params_base.speculative.cache_type_k;
+            params_dft.cache_type_v = params_base.speculative.cache_type_v;
 
             llama_init_dft = common_init_from_params(params_dft);