mtmd: add batching API (#24384)

* mtmd: add batching API

* wip

* first working version (gemma4v)

* add arg

* nits

* wire up support_batch()

* fix 0.0 output embd

* fix audio

* nits

* refactor a bit

* nits

* fix non-batching case

* fix comment

common/arg.cpp

@@ -2243,6 +2243,13 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
             params.image_max_tokens = value;
         }
     ).set_examples(mmproj_examples).set_env("LLAMA_ARG_IMAGE_MAX_TOKENS"));
+    add_opt(common_arg(
+        {"--mtmd-batch-max-tokens"}, "N",
+        string_format("maximum number of image tokens per batch when encoding images (default: %d)", params.mtmd_batch_max_tokens),
+        [](common_params & params, int value) {
+            params.mtmd_batch_max_tokens = value;
+        }
+    ).set_examples({LLAMA_EXAMPLE_SERVER}).set_env("LLAMA_ARG_MTMD_BATCH_MAX_TOKENS"));
     if (llama_supports_rpc()) {
         add_opt(common_arg(
             {"--rpc"}, "SERVERS",

common/common.h

@@ -575,6 +575,7 @@ struct common_params {
     std::vector<std::string> image; // path to image file(s) ; TODO: change the name to "media"
     int image_min_tokens = -1;
     int image_max_tokens = -1;
+    int mtmd_batch_max_tokens = 1024;
 
     // finetune
     struct lr_opt lr;