Files
mlx/mlx/backend/accelerate/quantized.cpp
T
Alex Barron d15fa13daf Batched Quantized Matmul + Fast Small QMV (#1503)
* add fast qmv for small dims

* fix test

* batched cpu

* add batched template param

* refactor metal quantized.cpp
2024-10-21 16:23:17 -07:00

118 lines
2.7 KiB
C++

// Copyright © 2023 Apple Inc.
#include <cassert>
#include <simd/vector.h>
#include "mlx/primitives.h"
namespace mlx::core {
namespace {
void _qmm_t_4_64(
float* result,
const float* x,
const uint32_t* w,
const float* scales,
const float* biases,
int M,
int N,
int K,
int B,
bool batched_w) {
constexpr int bits = 4;
constexpr int group_size = 64;
constexpr int bitmask = (1 << bits) - 1;
constexpr int pack_factor = 32 / bits;
constexpr int packs_in_group = group_size / pack_factor;
int w_els = N * K / pack_factor;
int g_els = w_els * pack_factor / group_size;
for (int i = 0; i < B; i++) {
for (int m = 0; m < M; m++) {
const uint32_t* w_local = w;
const float* scales_local = scales;
const float* biases_local = biases;
for (int n = 0; n < N; n++) {
const simd_float16* x_local = (simd_float16*)x;
simd_float16 sum = 0;
for (int k = 0; k < K; k += group_size) {
float scale = *scales_local++;
float bias = *biases_local++;
for (int kw = 0; kw < packs_in_group; kw += 2) {
// TODO: vectorize this properly
simd_uint16 wi;
for (int e = 0; e < 2; e++) {
uint32_t wii = *w_local++;
for (int p = 0; p < 8; p++) {
wi[e * 8 + p] = wii & bitmask;
wii >>= bits;
}
}
simd_float16 wf = simd_float(wi);
wf *= scale;
wf += bias;
sum += (*x_local) * wf;
x_local++;
}
}
*result = simd_reduce_add(sum);
result++;
}
x += K;
}
if (batched_w) {
w += w_els;
scales += g_els;
biases += g_els;
}
}
}
} // namespace
void QuantizedMatmul::eval_cpu(const std::vector<array>& inputs, array& out) {
assert(inputs.size() == 4);
auto& x = inputs[0];
auto& w = inputs[1];
auto& scales = inputs[2];
auto& biases = inputs[3];
bool condition =
(transpose_ && x.flags().row_contiguous && w.flags().row_contiguous &&
scales.flags().row_contiguous && biases.flags().row_contiguous &&
x.dtype() == float32 && bits_ == 4 && group_size_ == 64);
if (condition) {
out.set_data(allocator::malloc_or_wait(out.nbytes()));
int K = x.shape(-1);
int M = x.shape(-2);
int N = out.shape(-1);
int B = x.size() / K / M;
bool batched_w = w.ndim() > 2;
_qmm_t_4_64(
out.data<float>(),
x.data<float>(),
w.data<uint32_t>(),
scales.data<float>(),
biases.data<float>(),
M,
N,
K,
B,
batched_w);
} else {
eval(inputs, out);
}
}
} // namespace mlx::core