// Set a callback to be called for each resulting node during graph compute
GGML_API void ggml_backend_sched_set_eval_callback(ggml_backend_sched_t sched, ggml_backend_sched_eval_callback callback, void * user_data);
+ //
+ // Meta backend
+ //
+
+#define GGML_BACKEND_META_MAX_DEVICES 16
+
+ enum ggml_backend_meta_split_axis {
+ // tensor split by tensor dimensions:
+ GGML_BACKEND_SPLIT_AXIS_0 = 0,
+ GGML_BACKEND_SPLIT_AXIS_1 = 1,
+ GGML_BACKEND_SPLIT_AXIS_2 = 2,
+ GGML_BACKEND_SPLIT_AXIS_3 = 3,
+
+ GGML_BACKEND_SPLIT_AXIS_MIRRORED = 10, // all values on all backends
+ GGML_BACKEND_SPLIT_AXIS_PARTIAL = 11, // each backend has a partial sum
+
+ // for internal bookkeeping only:
+ GGML_BACKEND_SPLIT_AXIS_NONE = 98,
+ GGML_BACKEND_SPLIT_AXIS_UNKNOWN = 99,
+ };
+ GGML_API const char * ggml_backend_meta_split_axis_name(enum ggml_backend_meta_split_axis split_axis);
+
+ struct ggml_backend_meta_split_state {
+ enum ggml_backend_meta_split_axis axis;
+
+ // for tensors with axis >= 0 && axis < GGML_MAX_DIMS:
+ // - each device has a slice of the tensor along the split axis
+ // - most tensors have n_segments == 1 and a contiguous slice of the tensor data
+ // - some tensors have an inhomogenenous data layout along the split axis,
+ // those tensors are divided into segments which are each individually split across devices
+ // - ne has one entry per segment and device that add up to ggml_tensor::ne for that axis,
+ // the outer/inner loops are over segments/devices like [seg0_dev0, seg0_dev1, seg1_dev0, seg1_dev1],
+ // - for example, a transformer may have a fused QKV matrix rather than 3 matrices, those would be 3 separate segments
+ // that each need to be split individually across devices so that each device gets a slice of Q, K, and V
+ int64_t ne[16*GGML_BACKEND_META_MAX_DEVICES];
+ uint32_t n_segments;
+ };
+
+ // function to assign split states for statically allocated tensors, compute tensor split states will be assigned to be compatible:
+ typedef struct ggml_backend_meta_split_state(*ggml_backend_meta_get_split_state_t)(const struct ggml_tensor * tensor, void * userdata);
+
+ // create a new meta device from "simple" devices, meta buffer type/buffer/backend is then derived from this:
+ // TODO: this looks a bit strange - a backend API creates a device. I think we should try
+ // express this as a backend registry functionality instead
+ GGML_API ggml_backend_dev_t ggml_backend_meta_device(
+ ggml_backend_dev_t * devs, size_t n_devs, ggml_backend_meta_get_split_state_t get_split_state, void * get_split_state_ud);
+
//
// Utils
//