Multi GPU support, CUDA refactor, CUDA scratch buffer (#1703)

* CUDA multi GPU + scratch

ggml_cuda_compute_forward

Tensor parallelism

ggml_cuda_add

ggml_cuda_rms_norm

ggml_cuda_silu

CUDA scratch buffer

--main-gpu CLI option

1 files changed, 28 insertions, 6 deletions

diff --git a/ggml.h b/ggml.h
index d1ba15f..1b26da3 100644
--- a/ggml.h
+++ b/ggml.h
@@ -256,8 +256,8 @@ extern "C" {
 
     enum ggml_backend {
         GGML_BACKEND_CPU = 0,
-        GGML_BACKEND_CUDA = 1,
-        GGML_BACKEND_CL = 2,
+        GGML_BACKEND_GPU = 10,
+        GGML_BACKEND_GPU_SPLIT = 20,
     };
 
     // model file types
@@ -387,7 +387,9 @@ extern "C" {
 
         char name[GGML_MAX_NAME];
 
-        char padding[16];
+        void * extra; // extra things e.g. for ggml-cuda.cu
+
+        char padding[4];
     };
 
     static const size_t GGML_TENSOR_SIZE = sizeof(struct ggml_tensor);
@@ -425,6 +427,25 @@ extern "C" {
         bool   no_alloc;   // don't allocate memory for the tensor data
     };
 
+
+    // compute types
+    enum ggml_task_type {
+        GGML_TASK_INIT = 0,
+        GGML_TASK_COMPUTE,
+        GGML_TASK_FINALIZE,
+    };
+
+    struct ggml_compute_params {
+        enum ggml_task_type type;
+
+        // ith = thread index, nth = number of threads
+        int ith, nth;
+
+        // work buffer for all threads
+        size_t wsize;
+        void * wdata;
+    };
+
     // misc
 
     GGML_API void    ggml_time_init(void); // call this once at the beginning of the program
@@ -436,9 +457,10 @@ extern "C" {
     GGML_API void    ggml_print_object (const struct ggml_object * obj);
     GGML_API void    ggml_print_objects(const struct ggml_context * ctx);
 
-    GGML_API int64_t ggml_nelements(const struct ggml_tensor * tensor);
-    GGML_API int64_t ggml_nrows    (const struct ggml_tensor * tensor);
-    GGML_API size_t  ggml_nbytes   (const struct ggml_tensor * tensor);
+    GGML_API int64_t ggml_nelements   (const struct ggml_tensor * tensor);
+    GGML_API int64_t ggml_nrows       (const struct ggml_tensor * tensor);
+    GGML_API size_t  ggml_nbytes      (const struct ggml_tensor * tensor);
+    GGML_API size_t  ggml_nbytes_split(const struct ggml_tensor * tensor, int nrows_split);
 
     GGML_API int     ggml_blck_size (enum ggml_type type);
     GGML_API size_t  ggml_type_size (enum ggml_type type); // size in bytes for all elements in a block