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llama.cpp/ggml/src/ggml-cuda/fattn-tile.cu

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#include "common.cuh"
#include "fattn-common.cuh"
#include "fattn-tile.cuh"
#define FATTN_TILE_NTHREADS 256
static int fattn_tile_get_kq_stride_host(const int D, const int ncols, const int cc, const int warp_size) {
if (GGML_CUDA_CC_IS_AMD(cc)) {
switch (D) {
case 64:
return ncols <= 16 ? 32 : 64;
case 128:
return ncols <= 16 ? 64 : warp_size;
case 256:
return 64;
default:
GGML_ABORT("fatal error");
return -1;
}
}
if (fast_fp16_available(cc)) {
switch (D) {
case 64:
case 128:
return 128;
case 256:
return ncols <= 16 ? 128 : 64;
default:
GGML_ABORT("fatal error");
return -1;
}
}
switch (D) {
case 64:
return ncols <= 16 ? 128 : 64;
case 128:
return ncols <= 16 ? 64 : 32;
case 256:
return 32;
default:
GGML_ABORT("fatal error");
return -1;
}
}
static constexpr __device__ int fattn_tile_get_kq_stride_device(int D, int ncols, int warp_size) {
#ifdef GGML_USE_HIP
switch (D) {
case 64:
return ncols <= 16 ? 32 : 64;
case 128:
return ncols <= 16 ? 64 : warp_size;
case 256:
return 64;
default:
return -1;
}
#else
#ifdef FAST_FP16_AVAILABLE
switch (D) {
case 64:
case 128:
return 128;
case 256:
return ncols <= 16 ? 128 : 64;
default:
return -1;
}
#else
switch (D) {
case 64:
return ncols <= 16 ? 128 : 64;
case 128:
return ncols <= 16 ? 64 : 32;
case 256:
return 32;
default:
return -1;
}
#endif // FAST_FP16_AVAILABLE
#endif // GGML_USE_HIP
GGML_UNUSED_VARS(ncols, warp_size);
}
static constexpr __device__ int fattn_tile_get_kq_nbatch_device(int D, int ncols, int warp_size) {
#ifdef GGML_USE_HIP
switch (D) {
case 64:
return 64;
case 128:
return ncols <= 16 ? 2*warp_size : 128;
case 256:
return ncols <= 16 ? 128 : 2*warp_size;
default:
return -1;
}
#else
#ifdef FAST_FP16_AVAILABLE
switch (D) {
case 64:
return 64;
case 128:
return ncols <= 16 ? 128 : 64;
case 256:
return ncols <= 16 ? 64 : 128;
default:
return -1;
}
#else
switch (D) {
case 64:
return 64;
case 128:
return 128;
case 256:
return ncols <= 16 ? 128 : 64;
default:
return -1;
}
#endif // FAST_FP16_AVAILABLE
#endif // GGML_USE_HIP
GGML_UNUSED_VARS(ncols, warp_size);
}
template<int D, int ncols, bool use_logit_softcap> // D == head size
#ifdef GGML_USE_HIP
__launch_bounds__(FATTN_TILE_NTHREADS, 1)
#else
__launch_bounds__(FATTN_TILE_NTHREADS, 2)
#endif // GGML_USE_HIP
static __global__ void flash_attn_tile(
const char * __restrict__ Q,
const char * __restrict__ K,
const char * __restrict__ V,
const char * __restrict__ mask,
const char * __restrict__ sinks,
const int * __restrict__ KV_max,
float * __restrict__ dst,
float2 * __restrict__ dst_meta,
const float scale,
const float max_bias,
const float m0,
const float m1,
const uint32_t n_head_log2,
const float logit_softcap,
const int32_t ne00, const int32_t ne01, const int32_t ne02, const int32_t ne03,
const int32_t nb01, const int32_t nb02, const int32_t nb03,
const int32_t ne10, const int32_t ne11, const int32_t ne12, const int32_t ne13,
const int32_t nb11, const int32_t nb12, const int64_t nb13,
const int32_t nb21, const int32_t nb22, const int64_t nb23,
const int32_t ne31, const int32_t ne32, const int32_t ne33,
const int32_t nb31, const int32_t nb32, const int64_t nb33) {
#ifdef FLASH_ATTN_AVAILABLE
// Skip unused kernel variants for faster compilation:
#ifdef FP16_MMA_AVAILABLE
NO_DEVICE_CODE;
return;
#endif // FP16_MMA_AVAILABLE
if (use_logit_softcap && !(D == 128 || D == 256)) {
GGML_UNUSED_VARS(Q, K, V, mask, sinks, KV_max, dst, dst_meta, scale,
max_bias, m0, m1, n_head_log2, logit_softcap,
ne00, ne01, ne02, ne03,
nb01, nb02, nb03,
ne10, ne11, ne12, ne13,
nb11, nb12, nb13,
nb21, nb22, nb23,
ne31, ne32, ne33,
nb31, nb32, nb33);
NO_DEVICE_CODE;
return;
}
constexpr int warp_size = 32;
constexpr int nwarps = FATTN_TILE_NTHREADS / warp_size;
constexpr int kq_stride = fattn_tile_get_kq_stride_device(D, ncols, warp_size);
static_assert(kq_stride % warp_size == 0, "kq_stride not divisable by warp_size.");
constexpr int kq_nbatch = fattn_tile_get_kq_nbatch_device(D, ncols, warp_size);
static_assert(kq_nbatch % (2*warp_size) == 0, "bad kq_nbatch");
// In this kernel Q, K, V are matrices while i, j, k are matrix indices.
const int ic0 = blockIdx.x * ncols; // Index of the Q/QKV column to work on.
const int sequence = blockIdx.z / ne02;
const int head = blockIdx.z - sequence*ne02;
const int gqa_ratio = ne02 / ne12; // With grouped query attention there are > 1 Q matrices per K, V matrix.
const float2 * Q_f2 = (const float2 *) (Q + nb03* sequence + nb02* head + nb01*ic0);
const half2 * K_h2 = (const half2 *) (K + nb13* sequence + nb12*(head / gqa_ratio));
const half2 * V_h2 = (const half2 *) (V + nb13* sequence + nb12*(head / gqa_ratio)); // K and V have same shape
const half * maskh = (const half *) (mask + nb33*(sequence % ne33) + nb31*ic0);
const float * sinksf = (const float *) (sinks);
const int stride_KV2 = nb11 / sizeof(half2);
const float slope = get_alibi_slope(max_bias, head, n_head_log2, m0, m1);
__shared__ float KQ[ncols][kq_stride];
#ifdef FAST_FP16_AVAILABLE
__shared__ half2 Q_tmp[ncols][D/2];
__shared__ half2 KV_tmp_h2[kq_stride * (kq_nbatch/2 + 1)]; // Padded to avoid memory bank conflicts.
half2 VKQ[ncols/nwarps][D/(2*warp_size)] = {{{0.0f, 0.0f}}};
#else
__shared__ float Q_tmp[ncols][D];
__shared__ float KV_tmp_f[kq_stride * (kq_nbatch + 1)]; // Padded to avoid memory bank conflicts.
float2 * KV_tmp_f2 = (float2 *) KV_tmp_f;
float2 VKQ[ncols/nwarps][D/(2*warp_size)] = {{{0.0f, 0.0f}}};
#endif // FAST_FP16_AVAILABLE
float kqmax[ncols/nwarps];
#pragma unroll
for (int j0 = 0; j0 < ncols; j0 += nwarps) {
kqmax[j0/nwarps] = -FLT_MAX/2.0f;
}
float kqsum[ncols/nwarps] = {0.0f};
#pragma unroll
for (int j0 = 0; j0 < ncols; j0 += nwarps) {
const int j = j0 + threadIdx.y;
#pragma unroll
for (int i0 = 0; i0 < D/2; i0 += warp_size) {
const float2 tmp = ic0 + j < ne01 ? Q_f2[j*(nb01/sizeof(float2)) + i0 + threadIdx.x] : make_float2(0.0f, 0.0f);
#ifdef FAST_FP16_AVAILABLE
Q_tmp[j][i0 + threadIdx.x] = make_half2(tmp.x * scale, tmp.y * scale);
#else
Q_tmp[j][2*i0 + threadIdx.x] = tmp.x * scale;
Q_tmp[j][2*i0 + warp_size + threadIdx.x] = tmp.y * scale;
#endif // FAST_FP16_AVAILABLE
}
}
__syncthreads();
const int k_VKQ_max = KV_max ? KV_max[sequence*gridDim.x + blockIdx.x] : ne11;
for (int k_VKQ_0 = blockIdx.y*kq_stride; k_VKQ_0 < k_VKQ_max; k_VKQ_0 += gridDim.y*kq_stride) {
// Calculate KQ tile and keep track of new maximum KQ values:
float kqmax_new[ncols/nwarps];
#pragma unroll
for (int j = 0; j < ncols/nwarps; ++j) {
kqmax_new[j] = kqmax[j];
}
float sum[kq_stride/warp_size][ncols/nwarps] = {{0.0f}};
#pragma unroll
for (int k_KQ_0 = 0; k_KQ_0 < D; k_KQ_0 += kq_nbatch) {
#pragma unroll
for (int i_KQ_0 = 0; i_KQ_0 < kq_stride; i_KQ_0 += nwarps) {
const int i_KQ = i_KQ_0 + threadIdx.y;
#pragma unroll
for (int k_KQ_1 = 0; k_KQ_1 < kq_nbatch/2; k_KQ_1 += warp_size) {
const half2 tmp_h2 = K_h2[int64_t(k_VKQ_0 + i_KQ)*stride_KV2 + k_KQ_0/2 + k_KQ_1 + threadIdx.x];
#ifdef FAST_FP16_AVAILABLE
KV_tmp_h2[i_KQ*(kq_nbatch/2 + 1) + k_KQ_1 + threadIdx.x] = tmp_h2;
#else
const float2 tmp_f2 = __half22float2(tmp_h2);
KV_tmp_f[i_KQ*(kq_nbatch + 1) + 2*k_KQ_1 + threadIdx.x] = tmp_f2.x;
KV_tmp_f[i_KQ*(kq_nbatch + 1) + 2*k_KQ_1 + warp_size + threadIdx.x] = tmp_f2.y;
#endif // FAST_FP16_AVAILABLE
}
}
__syncthreads();
#ifdef FAST_FP16_AVAILABLE
#pragma unroll
for (int k_KQ_1 = 0; k_KQ_1 < kq_nbatch/2; ++k_KQ_1) {
half2 K_k[kq_stride/warp_size];
half2 Q_k[ncols/nwarps];
#else
#pragma unroll
for (int k_KQ_1 = 0; k_KQ_1 < kq_nbatch; ++k_KQ_1) {
float K_k[kq_stride/warp_size];
float Q_k[ncols/nwarps];
#endif // FAST_FP16_AVAILABLE
#pragma unroll
for (int i_KQ_0 = 0; i_KQ_0 < kq_stride; i_KQ_0 += warp_size) {
const int i_KQ = i_KQ_0 + threadIdx.x;
#ifdef FAST_FP16_AVAILABLE
K_k[i_KQ_0/warp_size] = KV_tmp_h2[i_KQ*(kq_nbatch/2 + 1) + k_KQ_1];
#else
K_k[i_KQ_0/warp_size] = KV_tmp_f [i_KQ*(kq_nbatch + 1) + k_KQ_1];
#endif // FAST_FP16_AVAILABLE
}
#pragma unroll
for (int j_KQ_0 = 0; j_KQ_0 < ncols; j_KQ_0 += nwarps) {
const int j_KQ = j_KQ_0 + threadIdx.y;
#ifdef FAST_FP16_AVAILABLE
Q_k[j_KQ_0/nwarps] = Q_tmp[j_KQ][k_KQ_0/2 + k_KQ_1];
#else
Q_k[j_KQ_0/nwarps] = Q_tmp[j_KQ][k_KQ_0 + k_KQ_1];
#endif // FAST_FP16_AVAILABLE
}
#pragma unroll
for (int i_KQ_0 = 0; i_KQ_0 < kq_stride; i_KQ_0 += warp_size) {
#pragma unroll
for (int j_KQ_0 = 0; j_KQ_0 < ncols; j_KQ_0 += nwarps) {
ggml_cuda_mad(sum[i_KQ_0/warp_size][j_KQ_0/nwarps], K_k[i_KQ_0/warp_size], Q_k[j_KQ_0/nwarps]);
}
}
}
if (k_KQ_0 + kq_nbatch < D) {
__syncthreads(); // Sync not needed on last iteration.
}
}
#pragma unroll
for (int i_KQ_0 = 0; i_KQ_0 < kq_stride; i_KQ_0 += warp_size) {
const int i_KQ = i_KQ_0 + threadIdx.x;
#pragma unroll
for (int j_KQ_0 = 0; j_KQ_0 < ncols; j_KQ_0 += nwarps) {
const int j_KQ = j_KQ_0 + threadIdx.y;
if (use_logit_softcap) {
sum[i_KQ_0/warp_size][j_KQ_0/nwarps] = logit_softcap * tanhf(sum[i_KQ_0/warp_size][j_KQ_0/nwarps]);
}
sum[i_KQ_0/warp_size][j_KQ_0/nwarps] += mask ? slope*__half2float(maskh[j_KQ*ne11 + k_VKQ_0 + i_KQ]) : 0.0f;
kqmax_new[j_KQ_0/nwarps] = fmaxf(kqmax_new[j_KQ_0/nwarps], sum[i_KQ_0/warp_size][j_KQ_0/nwarps]);
KQ[j_KQ][i_KQ] = sum[i_KQ_0/warp_size][j_KQ_0/nwarps];
}
}
__syncthreads();
#pragma unroll
for (int j0 = 0; j0 < ncols; j0 += nwarps) {
const int j = j0 + threadIdx.y;
kqmax_new[j0/nwarps] = warp_reduce_max<warp_size>(kqmax_new[j0/nwarps]);
const float KQ_max_scale = expf(kqmax[j0/nwarps] - kqmax_new[j0/nwarps]);
kqmax[j0/nwarps] = kqmax_new[j0/nwarps];
float kqsum_add = 0.0f;
#pragma unroll
for (int i0 = 0; i0 < kq_stride; i0 += warp_size) {
const int i = i0 + threadIdx.x;
const float diff = KQ[j][i] - kqmax[j0/nwarps];
const float val = expf(diff);
kqsum_add += val;
KQ[j][i] = val;
}
kqsum[j0/nwarps] = kqsum[j0/nwarps]*KQ_max_scale + kqsum_add;
#ifdef FAST_FP16_AVAILABLE
const half2 KQ_max_scale_h2 = make_half2(KQ_max_scale, KQ_max_scale);
#pragma unroll
for (int i0 = 0; i0 < D/2; i0 += warp_size) {
VKQ[j0/nwarps][i0/warp_size] *= KQ_max_scale_h2;
}
#else
#pragma unroll
for (int i0 = 0; i0 < D/2; i0 += warp_size) {
VKQ[j0/nwarps][i0/warp_size].x *= KQ_max_scale;
VKQ[j0/nwarps][i0/warp_size].y *= KQ_max_scale;
}
#endif // FAST_FP16_AVAILABLE
}
constexpr int V_cols_per_iter = kq_stride*kq_nbatch / D;
static_assert(kq_stride % V_cols_per_iter == 0, "bad V_cols_per_iter");
#pragma unroll
for (int k0 = 0; k0 < kq_stride; k0 += V_cols_per_iter) {
#pragma unroll
for (int k1 = 0; k1 < V_cols_per_iter; k1 += nwarps) {
const int k_tile = k1 + threadIdx.y;
#pragma unroll
for (int i0 = 0; i0 < D/2; i0 += warp_size) {
const int i = i0 + threadIdx.x;
const half2 tmp = V_h2[int64_t(k_VKQ_0 + k0 + k_tile)*stride_KV2 + i];
#ifdef FAST_FP16_AVAILABLE
KV_tmp_h2[k_tile*(D/2) + i] = tmp;
#else
KV_tmp_f2[k_tile*(D/2) + i] = __half22float2(tmp);
#endif // FAST_FP16_AVAILABLE
}
}
__syncthreads();
#pragma unroll
for (int k1 = 0; k1 < V_cols_per_iter; ++k1) {
#ifdef FAST_FP16_AVAILABLE
half2 V_k[(D/2)/warp_size];
half2 KQ_k[ncols/nwarps];
#else
float2 V_k[(D/2)/warp_size];
float KQ_k[ncols/nwarps];
#endif // FAST_FP16_AVAILABLE
#pragma unroll
for (int i0 = 0; i0 < D/2; i0 += warp_size) {
const int i = i0 + threadIdx.x;
#ifdef FAST_FP16_AVAILABLE
V_k[i0/warp_size] = KV_tmp_h2[k1*(D/2) + i];
#else
V_k[i0/warp_size] = KV_tmp_f2[k1*(D/2) + i];
#endif // FAST_FP16_AVAILABLE
}
#pragma unroll
for (int j0 = 0; j0 < ncols; j0 += nwarps) {
const int j = j0 + threadIdx.y;
#ifdef FAST_FP16_AVAILABLE
const float tmp = KQ[j][k0 + k1];
KQ_k[j0/nwarps] = make_half2(tmp, tmp);
#else
KQ_k[j0/nwarps] = KQ[j][k0 + k1];
#endif // FAST_FP16_AVAILABLE
}
#pragma unroll
for (int i0 = 0; i0 < D/2; i0 += warp_size) {
#pragma unroll
for (int j0 = 0; j0 < ncols; j0 += nwarps) {
#ifdef FAST_FP16_AVAILABLE
VKQ[j0/nwarps][i0/warp_size] += V_k[i0/warp_size] *KQ_k[j0/nwarps];
#else
VKQ[j0/nwarps][i0/warp_size].x += V_k[i0/warp_size].x*KQ_k[j0/nwarps];
VKQ[j0/nwarps][i0/warp_size].y += V_k[i0/warp_size].y*KQ_k[j0/nwarps];
#endif // FAST_FP16_AVAILABLE
}
}
}
__syncthreads();
}
}
// Attention sink: adjust running max and sum once per head
if (sinksf && blockIdx.y == 0) {
const float sink = sinksf[head];
#pragma unroll
for (int j0 = 0; j0 < ncols; j0 += nwarps) {
float kqmax_new_j = fmaxf(kqmax[j0/nwarps], sink);
kqmax_new_j = warp_reduce_max<warp_size>(kqmax_new_j);
const float KQ_max_scale = expf(kqmax[j0/nwarps] - kqmax_new_j);
kqmax[j0/nwarps] = kqmax_new_j;
const float val = expf(sink - kqmax[j0/nwarps]);
kqsum[j0/nwarps] = kqsum[j0/nwarps] * KQ_max_scale;
if (threadIdx.x == 0) {
kqsum[j0/nwarps] += val;
}
#ifdef FAST_FP16_AVAILABLE
const half2 KQ_max_scale_h2 = make_half2(KQ_max_scale, KQ_max_scale);
#pragma unroll
for (int i0 = 0; i0 < D/2; i0 += warp_size) {
VKQ[j0/nwarps][i0/warp_size] *= KQ_max_scale_h2;
}
#else
#pragma unroll
for (int i0 = 0; i0 < D/2; i0 += warp_size) {
VKQ[j0/nwarps][i0/warp_size].x *= KQ_max_scale;
VKQ[j0/nwarps][i0/warp_size].y *= KQ_max_scale;
}
#endif // FAST_FP16_AVAILABLE
}
}
float2 * dst2 = (float2 *) dst;
#pragma unroll
for (int j_VKQ_0 = 0; j_VKQ_0 < ncols; j_VKQ_0 += nwarps) {
const int j_VKQ = j_VKQ_0 + threadIdx.y;
if (ic0 + j_VKQ >= ne01) {
return;
}
float kqsum_j = kqsum[j_VKQ_0/nwarps];
kqsum_j = warp_reduce_sum<warp_size>(kqsum_j);
const int j_dst_unrolled = ((sequence*ne01 + ic0 + j_VKQ)*ne02 + head)*gridDim.y + blockIdx.y;
#pragma unroll
for (int i00 = 0; i00 < D/2; i00 += warp_size) {
const int i0 = i00 + threadIdx.x;
#ifdef FAST_FP16_AVAILABLE
float2 dst_val = __half22float2(VKQ[j_VKQ_0/nwarps][i0/warp_size]);
#else
float2 dst_val = VKQ[j_VKQ_0/nwarps][i0/warp_size];
#endif // FAST_FP16_AVAILABLE
if (gridDim.y == 1) {
dst_val.x /= kqsum_j;
dst_val.y /= kqsum_j;
}
dst2[j_dst_unrolled*(D/2) + i0] = dst_val;
}
if (gridDim.y != 1 && threadIdx.x == 0) {
dst_meta[j_dst_unrolled] = make_float2(kqmax[j_VKQ_0/nwarps], kqsum_j);
}
}
#else
GGML_UNUSED_VARS(Q, K, V, mask, sinks, KV_max, dst, dst_meta, scale,
max_bias, m0, m1, n_head_log2, logit_softcap,
ne00, ne01, ne02, ne03,
nb01, nb02, nb03,
ne10, ne11, ne12, ne13,
nb11, nb12, nb13,
nb21, nb22, nb23,
ne31, ne32, ne33,
nb31, nb32, nb33);
NO_DEVICE_CODE;
#endif // FLASH_ATTN_AVAILABLE
}
template <int D, bool use_logit_softcap>
static void launch_fattn_tile_switch_ncols(ggml_backend_cuda_context & ctx, ggml_tensor * dst) {
const ggml_tensor * Q = dst->src[0];
const int id = ggml_cuda_get_device();
const int cc = ggml_cuda_info().devices[id].cc;
const int warp_size = 32;
const int nwarps = FATTN_TILE_NTHREADS / warp_size;
constexpr size_t nbytes_shared = 0;
if (Q->ne[1] > 16) {
constexpr int cols_per_block = 32;
fattn_kernel_t fattn_kernel = flash_attn_tile<D, cols_per_block, use_logit_softcap>;
const int kq_stride = fattn_tile_get_kq_stride_host(D, cols_per_block, cc, warp_size);
launch_fattn<D, cols_per_block, 1>
(ctx, dst, fattn_kernel, nwarps, nbytes_shared, kq_stride, true, true, false, warp_size);
return;
}
constexpr int cols_per_block = 16;
fattn_kernel_t fattn_kernel = flash_attn_tile<D, cols_per_block, use_logit_softcap>;
const int kq_stride = fattn_tile_get_kq_stride_host(D, cols_per_block, cc, warp_size);
launch_fattn<D, cols_per_block, 1>
(ctx, dst, fattn_kernel, nwarps, nbytes_shared, kq_stride, true, true, false, warp_size);
}
template <bool use_logit_softcap>
static void launch_fattn_tile_switch_head_size(ggml_backend_cuda_context & ctx, ggml_tensor * dst) {
const ggml_tensor * Q = dst->src[0];
switch (Q->ne[0]) {
case 64: {
launch_fattn_tile_switch_ncols< 64, use_logit_softcap>(ctx, dst);
} break;
case 128: {
launch_fattn_tile_switch_ncols<128, use_logit_softcap>(ctx, dst);
} break;
case 256: {
launch_fattn_tile_switch_ncols<256, use_logit_softcap>(ctx, dst);
} break;
default: {
GGML_ABORT("Unsupported head size");
} break;
}
}
void ggml_cuda_flash_attn_ext_tile(ggml_backend_cuda_context & ctx, ggml_tensor * dst) {
const ggml_tensor * KQV = dst;
float logit_softcap;
memcpy(&logit_softcap, (const float *) KQV->op_params + 2, sizeof(float));
if (logit_softcap == 0.0f) {
constexpr bool use_logit_softcap = false;
launch_fattn_tile_switch_head_size<use_logit_softcap>(ctx, dst);
} else {
constexpr bool use_logit_softcap = true;
launch_fattn_tile_switch_head_size<use_logit_softcap>(ctx, dst);
}
}
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