llama : differentiate the KV dims in the attention (#4657)

* Add n_key_dim and n_value_dim

Some models use values that are not derived from `n_embd`.
Also remove `n_embd_head` and `n_embd_gqa` because it is not clear
which "head" is referred to (key or value).

Fix issue #4648.

* Fix `llm_build_kqv` to use `n_value_gqa`

* Rebase

* Rename variables

* Fix llm_build_kqv to be more generic wrt n_embd_head_k

* Update default values for n_embd_head_k and n_embd_head_v

Co-authored-by: Georgi Gerganov <[email protected]>

* Fix llm_load_tensors: the asserts were not backcompat

---------

Co-authored-by: Georgi Gerganov <[email protected]>

Author: postmasters

gguf-py/gguf/constants.py

@@ -46,6 +46,8 @@ class Attention:
         HEAD_COUNT_KV     = "{arch}.attention.head_count_kv"
         MAX_ALIBI_BIAS    = "{arch}.attention.max_alibi_bias"
         CLAMP_KQV         = "{arch}.attention.clamp_kqv"
+        KEY_LENGTH        = "{arch}.attention.key_length"
+        VALUE_LENGTH      = "{arch}.attention.value_length"
         LAYERNORM_EPS     = "{arch}.attention.layer_norm_epsilon"
         LAYERNORM_RMS_EPS = "{arch}.attention.layer_norm_rms_epsilon"
 

gguf-py/gguf/gguf_writer.py

@@ -333,6 +333,12 @@ def add_head_count(self, count: int) -> None:
     def add_head_count_kv(self, count: int) -> None:
         self.add_uint32(Keys.Attention.HEAD_COUNT_KV.format(arch=self.arch), count)
 
+    def add_key_length(self, length: int) -> None:
+        self.add_uint32(Keys.Attention.KEY_LENGTH.format(arch=self.arch), length)
+
+    def add_value_length(self, length: int) -> None:
+        self.add_uint32(Keys.Attention.VALUE_LENGTH.format(arch=self.arch), length)
+
     def add_max_alibi_bias(self, bias: float) -> None:
         self.add_float32(Keys.Attention.MAX_ALIBI_BIAS.format(arch=self.arch), bias)