cont : avoid --spec-use-checkpoints argument

common/arg.cpp

@@ -3538,20 +3538,6 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
             params.speculative.ngram_min_hits = value;
         }
     ).set_examples({LLAMA_EXAMPLE_SERVER}));
-    add_opt(common_arg(
-        {"--spec-use-checkpoints"}, "[on|off|auto]",
-        string_format("use checkpoints to rewind token history in recurrent models ('on', 'off', or 'auto', default: %s)",
-                        params.speculative.use_checkpoints ? "on" : "off"),
-        [](common_params & params, const std::string & value) {
-            if (is_truthy(value) || is_autoy(value)) {
-                params.speculative.use_checkpoints = true;
-            } else if (is_falsey(value)) {
-                params.speculative.use_checkpoints = false;
-            } else {
-                throw std::invalid_argument("invalid value for --spec-use-checkpoints");
-            }
-        }
-    ).set_examples({LLAMA_EXAMPLE_SERVER}));
     add_opt(common_arg(
         {"-ctkd", "--cache-type-k-draft"}, "TYPE",
         string_format(

common/common.h

@@ -326,7 +326,6 @@ struct common_params_speculative {
     uint16_t ngram_min_hits   =  1; // minimum hits at ngram/mgram lookup for mgram to be proposed
     bool     use_checkpoints  =  false; // use checkpoints to rewind in token history of recurrent models
 
-
     std::shared_ptr<common_ngram_mod> ngram_mod;
 
     std::string lookup_cache_static;  // path of static ngram cache file for lookup decoding           // NOLINT

common/speculative.cpp

@@ -910,13 +910,13 @@ enum common_speculative_type common_speculative_type_from_name(const std::string
     return it->second;
 }
 
-bool common_speculative_is_compat(llama_context * ctx_tgt) {
+common_speculative_compat_type common_speculative_is_compat(llama_context * ctx_tgt) {
     auto * mem = llama_get_memory(ctx_tgt);
     if (mem == nullptr) {
-        return false;
+        return COMMON_SPECULATIVE_COMPAT_TYPE_NO;
     }
 
-    bool res = true;
+    common_speculative_compat_type res = COMMON_SPECULATIVE_COMPAT_TYPE_FULL;
 
     llama_memory_clear(mem, true);
 
@@ -928,14 +928,14 @@ bool common_speculative_is_compat(llama_context * ctx_tgt) {
     int ret = llama_decode(ctx_tgt, llama_batch_get_one(tmp.data(), tmp.size()));
     if (ret != 0) {
         LOG_ERR("%s: llama_decode() failed: %d\n", __func__, ret);
-        res = false;
+        res = COMMON_SPECULATIVE_COMPAT_TYPE_NO;
         goto done;
     }
 
     // try to remove the last tokens
     if (!llama_memory_seq_rm(mem, 0, 1, -1)) {
         LOG_WRN("%s: the target context does not support partial sequence removal\n", __func__);
-        res = false;
+        res = COMMON_SPECULATIVE_COMPAT_TYPE_CKPT;
         goto done;
     }
 
@@ -1262,7 +1262,6 @@ struct common_speculative_session::impl {
             if (draft.empty()) {
                 // switch to non-draft inference
                 LOG_DBG("%s: draft of length 0 after denied checkpoint\n", __func__);
-                clear_draft();
                 return draft;
             }
             // we use the shortened draft of previous speculation

common/speculative.h

@@ -23,9 +23,15 @@ enum common_speculative_type common_speculative_type_from_name(const std::string
 // convert type to string
 std::string common_speculative_type_to_str(enum common_speculative_type type);
 
+enum common_speculative_compat_type {
+    COMMON_SPECULATIVE_COMPAT_TYPE_NO   = 0,
+    COMMON_SPECULATIVE_COMPAT_TYPE_FULL = 1,
+    COMMON_SPECULATIVE_COMPAT_TYPE_CKPT = 2,
+};
+
 // check if the llama_context is compatible for speculative decoding
 // note: clears the memory of the context
-bool common_speculative_is_compat(llama_context * ctx_tgt);
+common_speculative_compat_type common_speculative_is_compat(llama_context * ctx_tgt);
 
 common_speculative * common_speculative_init(
         common_params_speculative & params,

tools/server/server-context.cpp

@@ -860,9 +860,14 @@ private:
 
         slots.clear();
 
-        const bool can_spec = common_speculative_is_compat(ctx);
-        if (!can_spec) {
-            SRV_WRN("%s", "speculative decoding not supported by this context without checkpoints\n");
+        const auto spec_type = common_speculative_is_compat(ctx);
+        if (spec_type == COMMON_SPECULATIVE_COMPAT_TYPE_NO) {
+            SRV_WRN("%s", "speculative decoding not supported by this context\n");
+        }
+
+        if (spec_type == COMMON_SPECULATIVE_COMPAT_TYPE_CKPT) {
+            SRV_WRN("%s", "speculative decoding will use checkpoints\n");
+            params_base.speculative.use_checkpoints = true;
         }
 
         // initialize slots
@@ -881,7 +886,7 @@ private:
             slot.prompt.tokens.has_mtmd = mctx != nullptr;
 
             // try speculative decoding
-            if (can_spec || params_base.speculative.use_checkpoints) {
+            if (spec_type != COMMON_SPECULATIVE_COMPAT_TYPE_NO) {
                 if (mctx) {
                     SRV_ERR("%s\n", "speculative decoding is not supported with multimodal");
                     return false;