Files
ollama/x/ml/nn/attention.go
Daniel Hiltgen 33ee7168ba Add experimental MLX backend and engine with imagegen support (#13648)
* WIP - MLX backend with gemma3

* MLX: add cmake and go tag build toggles

To build the new MLX backend code:
  cmake --preset MLX
  cmake --build --preset MLX --parallel
  cmake --install build --component MLX
  go build -tags mlx .

Note: the main.go entrypoint for the MLX engine will change in a follow up commit.

* add experimental image generation runtime

* add experimental image generation runtime

* MLX: wire up cuda build for linux

* MLX: get dependencies correct and dedup

This is still too large for a unified github artifact, but is now "correct" for the mlx_cuda_v13
directory.

* fix relative link bug in dedup

* Add darwin build and readme

* add go build tag for mlx dependent code and wire up build_darwin.sh

* lint cleanup

* macos: build mlx for x86

This will be CPU only.

* cuda build instructions and fix drift from mlx bump

* stale comment

* Delete agent helper doc

* Clean up readme.md

* Revise README for tokenizer clarity and details

Updated README to clarify tokenizer functionality and removed correctness section.

---------

Co-authored-by: jmorganca <jmorganca@gmail.com>
2026-01-08 16:18:59 -08:00

104 lines
4.3 KiB
Go

package nn
import (
"fmt"
"github.com/ollama/ollama/x/kvcache"
"github.com/ollama/ollama/x/ml"
)
// Attention implements scaled dot-product attention for transformer models:
// Attention(Q, K, V) = softmax(QK^T/√d_k)V
//
// Parameters:
// - ctx: Context for tensor operations
// - query: Query tensor (Q) with shape [d_k, heads, seq_len_q]
// - key: Key tensor (K) with shape [d_k, kv_heads, seq_len_k], can be nil to read from cache only
// - value: Value tensor (V) with shape [d_v, kv_heads, seq_len_k], can be nil to read from cache only
// - scale: Scaling factor, typically 1/√d_k where d_k is the key dimension
// - cache: KV cache to store key/value and get past history, can be nil to only use provided key/value
//
// Returns:
//
// Attention output with shape [d_v, heads, seq_len_q]
func Attention(ctx ml.Context, query, key, value ml.Tensor, scale float64, cache kvcache.Cache) ml.Tensor {
return AttentionWithVMLA(ctx, query, key, value, nil, nil, scale, cache)
}
func AttentionWithSinks(ctx ml.Context, query, key, value, sinks ml.Tensor, scale float64, cache kvcache.Cache) ml.Tensor {
return AttentionWithVMLA(ctx, query, key, value, sinks, nil, scale, cache)
}
func AttentionWithVMLA(ctx ml.Context, query, key, value, sinks ml.Tensor, vmla ml.Tensor, scale float64, cache kvcache.Cache) ml.Tensor {
ctx.Forward(query)
if key != nil && value != nil {
if query.Dim(0) != key.Dim(0) {
panic(fmt.Errorf("d_k in attention operation does not match between query(%v) and key(%v)", query.Dim(0), key.Dim(0)))
}
if key.Dim(1) != value.Dim(1) {
panic(fmt.Errorf("kv_heads in attention operation does not match between key(%v) and value(%v)", key.Dim(1), value.Dim(1)))
}
if key.Dim(2) != value.Dim(2) {
panic(fmt.Errorf("seq_len_k in attention operation does not match between key(%v) and value(%v)", key.Dim(2), value.Dim(2)))
}
ctx.Forward(key, value)
if cache != nil {
cache.Put(ctx, key, value)
}
} else if cache == nil {
panic("key & value tensors must be provided if cache is nil")
}
// ctx.CompareWith("/tmp/test", map[string]ml.Tensor{"q": query, "k": key, "v": value}, true)
// panic("after cache get") //
// 2025/12/10 16:02:33 INFO XXX tensors are similar q=0.9999869465827942 shape="[1 8 13 256]" min_difference=[-0.07926178] max_difference=[0.07012844]
// 2025/12/10 16:02:33 INFO XXX tensors are similar k=0.9999891519546509 shape="[1 4 13 256]" min_difference=[-0.21365738] max_difference=[0.19916534]
// 2025/12/10 16:02:33 INFO XXX tensors are similar v=0.9999960660934448 shape="[1 4 13 256]" min_difference=[-0.32923126] max_difference=[0.32646942]
// var mask ml.Tensor
if cache != nil {
key, value, _ = cache.Get(ctx)
}
// ctx.CompareWith("/tmp/test", map[string]ml.Tensor{"q": query.Contiguous(ctx, false), "k": key.Contiguous(ctx, false), "v": value.Contiguous(ctx, false)}, true)
// panic("after cache get") //
// 2025/12/10 15:34:03 INFO XXX tensors are similar q=0.9999869465827942 shape="[1 8 13 256]" min_difference=[-0.07926178] max_difference=[0.07012844]
// 2025/12/10 15:34:03 INFO XXX tensors are similar k=0.9999881982803345 shape="[1 4 13 256]" min_difference=[-0.25] max_difference=[0.25]
// 2025/12/10 15:34:03 INFO XXX tensors are similar v=0.9999913573265076 shape="[1 4 13 256]" min_difference=[-0.5] max_difference=[0.5]
// Only use the fast SDPA implementation if we have a cache, since that's what
// will do any expected backend-specific transformations for us
if cache != nil {
// TODO what to do with vmla?
// return query.Transpose(ctx, 0, 2, 1, 3).ScaledDotProductAttention(ctx, key.Transpose(ctx, 0, 2, 1, 3), value.Transpose(ctx, 0, 2, 1, 3), scale, "array", mask, sinks)
return query.ScaledDotProductAttention(ctx, key, value, scale, "causal", nil, sinks)
// TODO these two produce identical output, but not similar enough - 92.9% - should be 99.999%
} else {
panic("else case not supported")
// TODO transpose shapes are wrong
// key = key.Transpose(ctx, 0, 2, 1, 3)
// value = value.Transpose(ctx, 1, 2, 0, 3).Contiguous(ctx, false)
// kq := query.Matmul(ctx, key)
// kq = kq.Scale(ctx, scale)
// if mask != nil {
// kq = kq.Add(ctx, mask)
// }
// kq = kq.Softmax(ctx)
// kqv := kq.Matmul(ctx, value)
// if vmla != nil {
// kqv = kqv.Matmul(ctx, vmla)
// }
// return kqv.Transpose(ctx, 0, 2, 1, 3).Contiguous(ctx, false)
}
}