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ggml-cuda: Repost of 21896: Blackwell native NVFP4 support (#22196)

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This commit is contained in:
Michael Wand
2026-04-29 06:47:42 +08:00
committed by GitHub
parent 7b8443ac78
commit fc2b0053ff
8 changed files with 318 additions and 130 deletions
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ggml/src/ggml-cuda/quantize.cu
+121 -21
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@@ -70,6 +70,102 @@ __device__ __forceinline__ uint8_t compute_e8m0_scale(float amax) {
return static_cast<uint8_t>(biased);
}
static __global__ void quantize_mmq_nvfp4(
const float * __restrict__ x, const int32_t * __restrict__ ids, void * __restrict__ vy,
const int64_t ne00, const int64_t s01, const int64_t s02, const int64_t s03,
const int64_t ne0, const int64_t ne1, const int64_t ne2) {
#if defined(BLACKWELL_MMA_AVAILABLE)
const int64_t i0_base = ((int64_t) blockDim.x * blockIdx.y + threadIdx.x) * QK_NVFP4_SUB;
if (i0_base >= ne0) {
return;
}
const int64_t i1 = blockIdx.x;
const int64_t i2 = blockIdx.z % ne2;
const int64_t i3 = blockIdx.z / ne2;
const int64_t i01 = ids ? ids[i1] : i1;
const int64_t k_block = i0_base / QK_K;
const int64_t blocks_per_col = (ne0 + QK_K - 1) / QK_K;
if (k_block >= blocks_per_col) {
return;
}
const int64_t ib = blockIdx.z * ((int64_t) blocks_per_col * ne1) + k_block * ne1 + blockIdx.x;
block_fp4_mmq * y = (block_fp4_mmq *) vy;
block_fp4_mmq * yb = y + ib;
const int sub = (i0_base % QK_K) / QK_NVFP4_SUB;
float vals_raw[QK_NVFP4_SUB];
float amax_raw = 0.0f;
const int64_t base_idx = i3 * s03 + i2 * s02 + i01 * s01;
#pragma unroll
for (int k = 0; k < QK_NVFP4_SUB; k++) {
const int64_t i00 = i0_base + k;
if (i00 < ne00) {
const float v = x[base_idx + i00];
vals_raw[k] = v;
amax_raw = fmaxf(amax_raw, fabsf(v));
} else {
vals_raw[k] = 0.0f;
}
}
static constexpr int test_offsets[5] = { 0, -1, 1, -2, 2};
const int first_fp8_code = (int) ggml_cuda_fp32_to_ue4m3(amax_raw / 6.0f);
float best_err = FLT_MAX;
uint8_t fp8_code = 0;
float subblock_scale = 0.0f;
#pragma unroll // Check +/- 2 to find best code to reduce NVFP4 activation loss. Negligible overhead on Blackwell.
for (int i = 0; i < 5; i++) {
const int test_code = first_fp8_code + test_offsets[i];
if (test_code < 0 || test_code > 0x7e) {
continue;
}
const uint8_t code = (uint8_t) test_code;
const float test_scale = ggml_cuda_ue4m3_to_fp32(code);
const float test_inv_scale = test_scale > 0.0f ? 0.5f / test_scale : 0.0f;
float cur_err = 0.0f;
#pragma unroll
for (int k = 0; k < QK_NVFP4_SUB; ++k) {
const float v = vals_raw[k];
const uint8_t q = ggml_cuda_float_to_fp4_e2m1(v, test_inv_scale);
const float err_diff = fabsf(v) - fabsf(kvalues_mxfp4[q & 0x7]) * test_scale;
cur_err = fmaf(err_diff, err_diff, cur_err);
}
if (cur_err < best_err) {
best_err = cur_err;
fp8_code = test_code;
subblock_scale = test_scale;
}
}
const float inv_scale = subblock_scale > 0.0f ? 0.5f / subblock_scale : 0.0f;
uint32_t q0 = 0;
uint32_t q1 = 0;
#pragma unroll // this is faster than the previous __nv_fp4x4_e2m1
for (int k = 0; k < QK_NVFP4_SUB / 4; ++k) {
q0 |= (uint32_t) ggml_cuda_float_to_fp4_e2m1(vals_raw[k + 0], inv_scale) << (8 * k);
q0 |= (uint32_t) ggml_cuda_float_to_fp4_e2m1(vals_raw[k + 8], inv_scale) << (8 * k + 4);
q1 |= (uint32_t) ggml_cuda_float_to_fp4_e2m1(vals_raw[k + 4], inv_scale) << (8 * k);
q1 |= (uint32_t) ggml_cuda_float_to_fp4_e2m1(vals_raw[k + 12], inv_scale) << (8 * k + 4);
}
uint32_t * yqs = reinterpret_cast<uint32_t *>(yb->qs);
yqs[2 * sub + 0] = q0;
yqs[2 * sub + 1] = q1;
reinterpret_cast<uint8_t *>(yb->d4)[sub] = fp8_code;
#else
NO_DEVICE_CODE; // This is for Blackwell NVFP4 activations only.
#endif // defined(BLACKWELL_MMA_AVAILABLE)
}
// quantize values in the format mxfp4 is stored which is interleaved nibbles
// i.e. a block a0-a31 is represented as a0a16,a1a17 ...a15a31
static __global__ void quantize_mmq_mxfp4(const float * __restrict__ x,
@@ -316,28 +412,32 @@ void quantize_mmq_q8_1_cuda(
}
}
void quantize_mmq_mxfp4_cuda(const float * x,
const int32_t * ids,
void * vy,
[[maybe_unused]] const ggml_type type_src0,
const int64_t ne00,
const int64_t s01,
const int64_t s02,
const int64_t s03,
const int64_t ne0,
const int64_t ne1,
const int64_t ne2,
const int64_t ne3,
cudaStream_t stream) {
GGML_ASSERT(ne0 % (2 * QK_MXFP4) == 0);
void quantize_mmq_fp4_cuda(
const float * x, const int32_t * ids, void * vy, const ggml_type type_src0,
const int64_t ne00, const int64_t s01, const int64_t s02, const int64_t s03,
const int64_t ne0, const int64_t ne1, const int64_t ne2, const int64_t ne3, cudaStream_t stream) {
GGML_ASSERT(type_src0 == GGML_TYPE_MXFP4 || type_src0 == GGML_TYPE_NVFP4);
GGML_ASSERT(ne0 > 0);
constexpr int nwarps = 8;
constexpr int vals_per_warp = 2 * QK_MXFP4;
constexpr int vals_per_block = nwarps * vals_per_warp;
if (type_src0 == GGML_TYPE_NVFP4) {
GGML_ASSERT(ne00 % QK_NVFP4 == 0);
constexpr int nvfp4_block_size = 128;
const int64_t block_num_y = (ne0 + QK_NVFP4_SUB * nvfp4_block_size - 1) / (QK_NVFP4_SUB * nvfp4_block_size);
const dim3 block_size(nvfp4_block_size, 1, 1);
const dim3 num_blocks(ne1, block_num_y, ne2 * ne3);
quantize_mmq_nvfp4<<<num_blocks, block_size, 0, stream>>>(
x, ids, vy, ne00, s01, s02, s03, ne0, ne1, ne2);
} else {
GGML_ASSERT(ne0 % (2 * QK_MXFP4) == 0);
const int64_t block_num_y = (ne0 + vals_per_block - 1) / vals_per_block;
const dim3 num_blocks(ne1, block_num_y, ne2 * ne3);
const dim3 block_size(WARP_SIZE, nwarps, 1);
constexpr int nwarps = 8;
constexpr int vals_per_warp = 2 * QK_MXFP4;
constexpr int vals_per_block = nwarps * vals_per_warp;
quantize_mmq_mxfp4<<<num_blocks, block_size, 0, stream>>>(x, ids, vy, ne00, s01, s02, s03, ne0, ne1, ne2);
const int64_t block_num_y = (ne0 + vals_per_block - 1) / vals_per_block;
const dim3 num_blocks(ne1, block_num_y, ne2 * ne3);
const dim3 block_size(WARP_SIZE, nwarps, 1);
quantize_mmq_mxfp4<<<num_blocks, block_size, 0, stream>>>(x, ids, vy, ne00, s01, s02, s03, ne0, ne1, ne2);
}
}