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CUDA: add bf16 and f32 support to cublas_mul_mat_batched #14361

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789c697
CUDA: add bf16 and f32 support to cublas_mul_mat_batched
am17an Jun 24, 2025
b7225ec
Review: add type traits and make function more generic
am17an Jun 25, 2025
87aeacf
Review: make check more explicit, add back comments, and fix formatting
am17an Jun 25, 2025
0608d77
Review: fix formatting, remove useless type conversion, fix naming fo…
am17an Jun 25, 2025
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22 changes: 22 additions & 0 deletions ggml/src/ggml-cuda/convert.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -728,3 +728,25 @@ to_fp16_nc_cuda_t ggml_get_to_fp16_nc_cuda(ggml_type type) {
return nullptr;
}
}

to_bf16_nc_cuda_t ggml_get_to_bf16_nc_cuda(ggml_type type) {
switch (type) {
case GGML_TYPE_F32:
return convert_unary_cuda<float, nv_bfloat16>;
case GGML_TYPE_F16:
return convert_unary_cuda<half, nv_bfloat16>;
default:
return nullptr;
}
}

to_fp32_nc_cuda_t ggml_get_to_fp32_nc_cuda(ggml_type type) {
switch (type) {
case GGML_TYPE_F16:
return convert_unary_cuda<half, float>;
case GGML_TYPE_BF16:
return convert_unary_cuda<nv_bfloat16, float>;
default:
return nullptr;
}
}
5 changes: 5 additions & 0 deletions ggml/src/ggml-cuda/convert.cuh
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Expand Up @@ -22,5 +22,10 @@ using to_t_nc_cuda_t = void (*)(const void * x, T * y,
int64_t ne00, int64_t ne01, int64_t ne02, int64_t ne03,
int64_t s01, int64_t s02, int64_t s03, cudaStream_t stream);

typedef to_t_nc_cuda_t<float> to_fp32_nc_cuda_t;
typedef to_t_nc_cuda_t<half> to_fp16_nc_cuda_t;
typedef to_t_nc_cuda_t<nv_bfloat16> to_bf16_nc_cuda_t;

to_fp32_nc_cuda_t ggml_get_to_fp32_nc_cuda(ggml_type type);
to_fp16_nc_cuda_t ggml_get_to_fp16_nc_cuda(ggml_type type);
to_bf16_nc_cuda_t ggml_get_to_bf16_nc_cuda(ggml_type type);
207 changes: 131 additions & 76 deletions ggml/src/ggml-cuda/ggml-cuda.cu
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Expand Up @@ -1746,7 +1746,7 @@ static void ggml_cuda_op_mul_mat(
}

static __global__ void k_compute_batched_ptrs(
const half * src0_as_f16, const half * src1_as_f16, char * dst,
const void * src0_as_f16, const void * src1_as_f16, char * dst,
const void ** ptrs_src, void ** ptrs_dst,
int64_t ne12, int64_t ne13,
int64_t ne23,
Expand All @@ -1769,91 +1769,139 @@ static __global__ void k_compute_batched_ptrs(
ptrs_dst[0*ne23 + i12 + i13*ne12] = ( char *) dst + i12*nbd2 + i13*nbd3;
}

static void ggml_cuda_mul_mat_batched_cublas(ggml_backend_cuda_context & ctx, const ggml_tensor * src0, const ggml_tensor * src1, ggml_tensor * dst) {
// Type traits for mapping ggml types to CUDA/cuBLAS types
template<ggml_type T>
struct batched_mul_mat_traits;

template<>
struct batched_mul_mat_traits<GGML_TYPE_F32> {
using cuda_type = float;
static inline const cublasComputeType_t compute_type = CUBLAS_COMPUTE_32F;
static inline const cudaDataType_t data_type = CUDA_R_32F;
static inline const ggml_type ggml_type_val = GGML_TYPE_F32;
static inline const float alpha = 1.0f;
static inline const float beta = 0.0f;
static inline const void* get_alpha() { static const float val = alpha; return &val; }
static inline const void* get_beta() { static const float val = beta; return &val; }
static inline auto get_nc_converter(ggml_type src_type) { return ggml_get_to_fp32_nc_cuda(src_type); }
};

template<>
struct batched_mul_mat_traits<GGML_TYPE_BF16> {
using cuda_type = nv_bfloat16;
static inline const cublasComputeType_t compute_type = CUBLAS_COMPUTE_32F;
static inline const cudaDataType_t data_type = CUDA_R_16BF;
static inline const ggml_type ggml_type_val = GGML_TYPE_BF16;
static inline const float alpha = 1.0f;
static inline const float beta = 0.0f;
static inline const void* get_alpha() { static const float val = alpha; return &val; }
static inline const void* get_beta() { static const float val = beta; return &val; }
static inline auto get_nc_converter(ggml_type src_type) { return ggml_get_to_bf16_nc_cuda(src_type); }
};

template<>
struct batched_mul_mat_traits<GGML_TYPE_F16> {
using cuda_type = half;
static inline const cublasComputeType_t compute_type = CUBLAS_COMPUTE_16F;
static inline const cudaDataType_t data_type = CUDA_R_16F;
static inline const ggml_type ggml_type_val = GGML_TYPE_F16;
static inline const half alpha = 1.0;
static inline const half beta = 0.0;
static inline const void* get_alpha() { static const half val = alpha; return &val; }
static inline const void* get_beta() { static const half val = beta; return &val; }
static inline auto get_nc_converter(ggml_type src_type) { return ggml_get_to_fp16_nc_cuda(src_type); }
};

template<ggml_type src0_type>
static void ggml_cuda_mul_mat_batched_cublas_impl(ggml_backend_cuda_context & ctx, const ggml_tensor * src0, const ggml_tensor * src1, ggml_tensor * dst) {
using traits = batched_mul_mat_traits<src0_type>;
using cuda_t = typename traits::cuda_type;

GGML_ASSERT(!ggml_is_transposed(src0));
GGML_ASSERT(!ggml_is_transposed(src1));

GGML_ASSERT(!ggml_backend_buft_is_cuda_split(src0->buffer->buft));
GGML_ASSERT(src0->type == GGML_TYPE_F16);
GGML_ASSERT(src0->type == src0_type);
GGML_ASSERT(ggml_is_contiguous(dst));

// Byte offsets and tensor dimensions are currently used in an inconsistent way for dst.
// As long as dst is contiguous this does not matter though.
GGML_ASSERT(ggml_is_contiguous(dst));

GGML_TENSOR_BINARY_OP_LOCALS

const int64_t ne_dst = ggml_nelements(dst);

cudaStream_t main_stream = ctx.stream();

CUBLAS_CHECK(cublasSetStream(ctx.cublas_handle(), main_stream));

const half * src0_f16 = (const half *) src0->data;
float * dst_ddf = (float *) dst->data;

const half * src1_f16 = (const half *) src1->data;
const size_t ts_src1 = ggml_type_size(src1->type);
GGML_ASSERT(nb10 == ts_src1);
int64_t s11 = nb11 / ts_src1;
int64_t s12 = nb12 / ts_src1;
int64_t s13 = nb13 / ts_src1;
ggml_cuda_pool_alloc<half> src1_f16_alloc(ctx.pool());

// convert src1 to fp16
if (src1->type != GGML_TYPE_F16) {
const to_fp16_nc_cuda_t to_fp16_cuda = ggml_get_to_fp16_nc_cuda(src1->type);
const int64_t ne_src1 = ggml_nelements(src1);
src1_f16_alloc.alloc(ne_src1);
GGML_ASSERT(to_fp16_cuda != nullptr);
const cuda_t * src0_ptr = nullptr;
const cuda_t * src1_ptr = nullptr;

to_fp16_cuda(src1_f16, src1_f16_alloc.get(), ne10, ne11, ne12, ne13, s11, s12, s13, main_stream);
ggml_cuda_pool_alloc<cuda_t> src0_alloc(ctx.pool());
ggml_cuda_pool_alloc<cuda_t> src1_alloc(ctx.pool());

// Handle src0
src0_ptr = (const cuda_t *) src0->data;

// Handle src1 - convert if necessary
if (src1->type == src0_type) {
src1_ptr = (const cuda_t *) src1->data;
} else {
// Convert src1 to target type using traits conversion functions
const int64_t ne_src1 = ggml_nelements(src1);
src1_alloc.alloc(ne_src1);

src1_f16 = src1_f16_alloc.get();
const auto convert_func = traits::get_nc_converter(src1->type);
GGML_ASSERT(convert_func != nullptr);
convert_func(src1->data, src1_alloc.get(), ne10, ne11, ne12, ne13, s11, s12, s13, main_stream);
src1_ptr = src1_alloc.get();
s11 = ne10;
s12 = ne11*s11;
s13 = ne12*s12;
}

ggml_cuda_pool_alloc<half> dst_f16(ctx.pool());
// Setup destination buffer
ggml_cuda_pool_alloc<cuda_t> dst_temp(ctx.pool());
char * dst_t;

cublasComputeType_t cu_compute_type = CUBLAS_COMPUTE_16F;
cudaDataType_t cu_data_type = CUDA_R_16F;

// dst strides
size_t nbd2 = dst->nb[2];
size_t nbd3 = dst->nb[3];

const half alpha_f16 = 1.0f;
const half beta_f16 = 0.0f;

cublasComputeType_t cu_compute_type = traits::compute_type;
cudaDataType_t cu_data_type = traits::data_type;
cudaDataType_t cu_data_type_a = traits::data_type;
cudaDataType_t cu_data_type_b = traits::data_type;
const void * alpha = traits::get_alpha();
const void * beta = traits::get_beta();
const float alpha_f32 = 1.0f;
const float beta_f32 = 0.0f;

const void * alpha = &alpha_f16;
const void * beta = &beta_f16;
const float beta_f32 = 0.0f;

if (dst->op_params[0] == GGML_PREC_DEFAULT) {
dst_t = (char *) dst_f16.alloc(ne_dst);

nbd2 /= sizeof(float) / sizeof(half);
nbd3 /= sizeof(float) / sizeof(half);
if constexpr (src0_type == GGML_TYPE_F32) {
dst_t = (char *) dst_ddf; // Direct F32 output
} else {
dst_t = (char *) dst_temp.alloc(ne_dst);
nbd2 /= sizeof(float) / sizeof(cuda_t);
nbd3 /= sizeof(float) / sizeof(cuda_t);
}
} else {
dst_t = (char *) dst_ddf;

cu_compute_type = CUBLAS_COMPUTE_32F;
cu_data_type = CUDA_R_32F;

cu_data_type = CUDA_R_32F;
alpha = &alpha_f32;
beta = &beta_f32;
beta = &beta_f32;
}

int id = ggml_cuda_get_device();
const int cc = ggml_cuda_info().devices[id].cc;
if (GGML_CUDA_CC_IS_CDNA(cc) || GGML_CUDA_CC_IS_RDNA4(cc)) {
cu_compute_type = CUBLAS_COMPUTE_32F;
alpha = &alpha_f32;
beta = &beta_f32;
beta = &beta_f32;
}

GGML_ASSERT(ne12 % ne02 == 0);
Expand All @@ -1863,35 +1911,15 @@ static void ggml_cuda_mul_mat_batched_cublas(ggml_backend_cuda_context & ctx, co
const int64_t r2 = ne12/ne02;
const int64_t r3 = ne13/ne03;

#if 0
// use cublasGemmEx
{
for (int i13 = 0; i13 < ne13; ++i13) {
for (int i12 = 0; i12 < ne12; ++i12) {
int i03 = i13 / r3;
int i02 = i12 / r2;

CUBLAS_CHECK(
cublasGemmEx(ctx.cublas_handle(), CUBLAS_OP_T, CUBLAS_OP_N,
ne01, ne11, ne10,
alpha, (const char *) src0_f16 + i03*nb03 + i02*nb02, CUDA_R_16F, nb01/sizeof(half),
src1_f16 + i13*s13 + i12*s12, CUDA_R_16F, s11,
beta, ( char *) dst_t + i13*nbd3 + i12*nbd2, cu_data_type, ne0,
cu_compute_type,
CUBLAS_GEMM_DEFAULT_TENSOR_OP));
}
}
}
#else
if (r2 == 1 && r3 == 1 && ggml_is_contiguous_2(src0) && ggml_is_contiguous_2(src1)) {
// there is no broadcast and src0, src1 are contiguous across dims 2, 3
// use cublasGemmStridedBatchedEx
CUBLAS_CHECK(
cublasGemmStridedBatchedEx(ctx.cublas_handle(), CUBLAS_OP_T, CUBLAS_OP_N,
ne01, ne11, ne10,
alpha, src0_f16, CUDA_R_16F, nb01/nb00, nb02/nb00, // strideA
src1_f16, CUDA_R_16F, s11, s12, // strideB
beta, dst_t, cu_data_type, ne0, ne1*ne0, // strideC
alpha, src0_ptr, cu_data_type_a, nb01/nb00, nb02/nb00, // strideA
src1_ptr, cu_data_type_b, s11, s12, // strideB
beta, dst_t, cu_data_type, ne0, ne1*ne0, // strideC
ne12*ne13,
cu_compute_type,
CUBLAS_GEMM_DEFAULT_TENSOR_OP));
Expand All @@ -1902,34 +1930,55 @@ static void ggml_cuda_mul_mat_batched_cublas(ggml_backend_cuda_context & ctx, co
ggml_cuda_pool_alloc<const void *> ptrs_src(ctx.pool(), 2*ne23);
ggml_cuda_pool_alloc< void *> ptrs_dst(ctx.pool(), 1*ne23);

size_t src1_stride_size = sizeof(cuda_t);

dim3 block_dims(ne13, ne12);
k_compute_batched_ptrs<<<1, block_dims, 0, main_stream>>>(
src0_f16, src1_f16, dst_t,
src0_ptr, src1_ptr, dst_t,
ptrs_src.get(), ptrs_dst.get(),
ne12, ne13,
ne23,
nb02, nb03,
src1->type == GGML_TYPE_F16 ? nb12 : s12*sizeof(half),
src1->type == GGML_TYPE_F16 ? nb13 : s13*sizeof(half),
(src1->type == src0_type) ? nb12 : s12*src1_stride_size,
(src1->type == src0_type) ? nb13 : s13*src1_stride_size,
nbd2, nbd3,
r2, r3);

CUDA_CHECK(cudaGetLastError());

CUBLAS_CHECK(
cublasGemmBatchedEx(ctx.cublas_handle(), CUBLAS_OP_T, CUBLAS_OP_N,
ne01, ne11, ne10,
alpha, (const void **) (ptrs_src.get() + 0*ne23), CUDA_R_16F, nb01/nb00,
(const void **) (ptrs_src.get() + 1*ne23), CUDA_R_16F, s11,
beta, ( void **) (ptrs_dst.get() + 0*ne23), cu_data_type, ne0,
alpha, (const void **) (ptrs_src.get() + 0*ne23), cu_data_type_a, nb01/nb00,
(const void **) (ptrs_src.get() + 1*ne23), cu_data_type_b, s11,
beta, ( void **) (ptrs_dst.get() + 0*ne23), cu_data_type, ne0,
ne23,
cu_compute_type,
CUBLAS_GEMM_DEFAULT_TENSOR_OP));
}
#endif

if (dst->op_params[0] == GGML_PREC_DEFAULT && cu_data_type == CUDA_R_16F) {
const to_fp32_cuda_t to_fp32_cuda = ggml_get_to_fp32_cuda(GGML_TYPE_F16);
to_fp32_cuda(dst_f16.get(), dst_ddf, ne_dst, main_stream);
// Convert output back to F32 if needed
if (dst->op_params[0] == GGML_PREC_DEFAULT && cu_data_type != CUDA_R_32F) {
const to_fp32_cuda_t to_fp32_cuda = ggml_get_to_fp32_cuda(traits::ggml_type_val);
to_fp32_cuda(dst_temp.get(), dst_ddf, ne_dst, main_stream);
}
}

static void ggml_cuda_mul_mat_batched_cublas(ggml_backend_cuda_context & ctx, const ggml_tensor * src0, const ggml_tensor * src1, ggml_tensor * dst) {
GGML_ASSERT(src0->type == GGML_TYPE_F16 || src0->type == GGML_TYPE_BF16 || src0->type == GGML_TYPE_F32);

switch (src0->type) {
case GGML_TYPE_F32:
ggml_cuda_mul_mat_batched_cublas_impl<GGML_TYPE_F32>(ctx, src0, src1, dst);
break;
case GGML_TYPE_BF16:
ggml_cuda_mul_mat_batched_cublas_impl<GGML_TYPE_BF16>(ctx, src0, src1, dst);
break;
case GGML_TYPE_F16:
ggml_cuda_mul_mat_batched_cublas_impl<GGML_TYPE_F16>(ctx, src0, src1, dst);
break;
default:
GGML_ABORT("Unsupported type");
}
}

Expand Down Expand Up @@ -1981,6 +2030,12 @@ static void ggml_cuda_mul_mat(ggml_backend_cuda_context & ctx, const ggml_tensor
//printf("src0 is contiguous %d, transposed %d, type = %s, name = %s\n", ggml_is_contiguous(src0), ggml_is_transposed(src0), ggml_type_name(src0->type), src0->name);
//printf("src1 is contiguous %d, transposed %d, type = %s, name = %s\n", ggml_is_contiguous(src1), ggml_is_transposed(src1), ggml_type_name(src1->type), src1->name);

//TODO update for generic tensor parallelism
const int cc = ggml_cuda_info().devices[ggml_cuda_get_device()].cc;
bool use_batched_cublas_f16 = src0->type == GGML_TYPE_F16 && (src1->type == GGML_TYPE_F16 || !any_gpus_with_slow_fp16);
bool use_batched_cublas_bf16 = src0->type == GGML_TYPE_BF16 && bf16_mma_hardware_available(cc);
bool use_batched_cublas_f32 = src0->type == GGML_TYPE_F32;

if (!split && use_mul_mat_vec) {
// the custom F16 vector kernel can be used over batched cuBLAS GEMM
// but this is only faster for GPUs without tensor cores or with a thin src0 matrix (particularly KQV in attention)
Expand All @@ -1989,8 +2044,8 @@ static void ggml_cuda_mul_mat(ggml_backend_cuda_context & ctx, const ggml_tensor
ggml_cuda_mul_mat_vec_q(ctx, src0, src1, nullptr, dst);
} else if (!split && use_mul_mat_q) {
ggml_cuda_mul_mat_q(ctx, src0, src1, nullptr, dst);
} else if (!split && src0->type == GGML_TYPE_F16 && (src1->type == GGML_TYPE_F16 || !any_gpus_with_slow_fp16) &&
!ggml_is_transposed(src0) && !ggml_is_transposed(src1) && src1->ne[2]*src1->ne[3] > 1) {
} else if (!split && (use_batched_cublas_f16 || use_batched_cublas_bf16 || use_batched_cublas_f32)
&& !ggml_is_transposed(src0) && !ggml_is_transposed(src1) && src1->ne[2]*src1->ne[3] > 1) {
// general KQ + KQV multi-batch without FlashAttention
ggml_cuda_mul_mat_batched_cublas(ctx, src0, src1, dst);
} else if (use_mul_mat_vec) {
Expand Down
6 changes: 4 additions & 2 deletions tests/test-backend-ops.cpp
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Expand Up @@ -4332,8 +4332,10 @@ static std::vector<std::unique_ptr<test_case>> make_test_cases_eval() {
for (auto nr : {1,4}) {
for (uint32_t m = 0; m < 2; ++m) {
for (uint32_t k = 0; k < 2; ++k) {
test_cases.emplace_back(new test_mul_mat(GGML_TYPE_F16, GGML_TYPE_F32, 1056 + m, 1, 128 + k, {bs, 1}, {nr, 1}, {0, 2, 1, 3}));
test_cases.emplace_back(new test_mul_mat(GGML_TYPE_F16, GGML_TYPE_F32, 128 + m, 1, 1056 + k, {bs, 1}, {nr, 1}, {0, 1, 2, 3}, true));
for (ggml_type type: {GGML_TYPE_F16, GGML_TYPE_BF16, GGML_TYPE_F32}) {
test_cases.emplace_back(new test_mul_mat(type, GGML_TYPE_F32, 1056 + m, 1, 128 + k, {bs, 1}, {nr, 1}, {0, 2, 1, 3}));
test_cases.emplace_back(new test_mul_mat(type, GGML_TYPE_F32, 128 + m, 1, 1056 + k, {bs, 1}, {nr, 1}, {0, 1, 2, 3}, true));
}
}
}
}
Expand Down
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