CUDA: add fast walsh-hadamard transform (#23615)

* CUDA: add fast walsh-hadamard transform

* review: add unrolls + change size_t -> int

* warp size 64

---------

Co-authored-by: Johannes Gäßler <johannesg@5d6.de>

ggml/src/ggml-cuda/fwht.cu

@@ -0,0 +1,108 @@
+#include "common.cuh"
+#include "fwht.cuh"
+
+template <int N>
+__launch_bounds__(4*ggml_cuda_get_physical_warp_size(), 1)
+__global__ void fwht_cuda(const float * src, float * dst, const int64_t n_rows, const float scale) {
+    constexpr int warp_size = ggml_cuda_get_physical_warp_size();
+
+    const int64_t r = (int64_t) blockIdx.x * blockDim.y + threadIdx.y;
+
+    if (r >= n_rows) {
+        return;
+    }
+
+    src += r * N;
+    dst += r * N;
+
+    static constexpr int el_w = N / warp_size;
+    float     reg[el_w];
+    const int lane = threadIdx.x;
+
+#pragma unroll
+    for (int i = 0; i < el_w; ++i) {
+        reg[i] = src[i * warp_size + lane] * scale;
+    }
+
+#pragma unroll
+    for (int h = 1; h < warp_size; h *= 2) {
+#pragma unroll
+        for (int j = 0; j < el_w; j++) {
+            const float val  = reg[j];
+            const float val2 = __shfl_xor_sync(0xFFFFFFFF, val, h, warp_size);
+
+            reg[j] = (lane & h) == 0 ? val + val2 : val2 - val;
+        }
+    }
+
+#pragma unroll
+    for (int h = warp_size; h < N; h *= 2) {
+        const int step = h / warp_size;
+#pragma unroll
+        for (int j = 0; j < el_w; j += 2 * step) {
+#pragma unroll
+            for (int k = 0; k < step; k++) {
+                const float x = reg[j + k];
+                const float y = reg[j + k + step];
+
+                reg[j + k]        = x + y;
+                reg[j + k + step] = x - y;
+            }
+        }
+    }
+
+#pragma unroll
+    for (int i = 0; i < el_w; ++i) {
+        dst[i * warp_size + lane] = reg[i];
+    }
+}
+
+void ggml_cuda_op_fwht(ggml_backend_cuda_context & ctx, const ggml_tensor * src, ggml_tensor * dst) {
+    GGML_ASSERT(ggml_are_same_shape(src, dst));
+    GGML_ASSERT(ggml_is_contiguous(src));
+    GGML_ASSERT(ggml_is_contiguous(dst));
+    const int     n    = src->ne[0];
+    const int64_t rows = ggml_nrows(src);
+
+    const float * src_d = (const float *) src->data;
+    float *       dst_d = (float *) dst->data;
+
+    const int warp_size = ggml_cuda_info().devices[ggml_cuda_get_device()].warp_size;
+    GGML_ASSERT(n % warp_size == 0);
+    const int rows_per_block = 4;
+
+    const int64_t num_blocks = (rows + rows_per_block - 1) / rows_per_block;
+
+    cudaStream_t                         stream = ctx.stream();
+    dim3                                 grid_dims(num_blocks, 1, 1);
+    dim3                                 block_dims(warp_size, rows_per_block, 1);
+    const ggml_cuda_kernel_launch_params launch_params =
+        ggml_cuda_kernel_launch_params(grid_dims, block_dims, 0, stream);
+
+    const float scale = 1 / sqrtf(n);
+
+    switch (n) {
+        case 64:
+            {
+                ggml_cuda_kernel_launch(fwht_cuda<64>, launch_params, src_d, dst_d, rows, scale);
+                break;
+            }
+        case 128:
+            {
+                ggml_cuda_kernel_launch(fwht_cuda<128>, launch_params, src_d, dst_d, rows, scale);
+                break;
+            }
+        case 256:
+            {
+                ggml_cuda_kernel_launch(fwht_cuda<256>, launch_params, src_d, dst_d, rows, scale);
+                break;
+            }
+        case 512:
+            {
+                ggml_cuda_kernel_launch(fwht_cuda<512>, launch_params, src_d, dst_d, rows, scale);
+                break;
+            }
+        default:
+            GGML_ABORT("fatal error");
+    }
+}

ggml/src/ggml-cuda/fwht.cuh

@@ -0,0 +1,3 @@
+#include "common.cuh"
+
+void ggml_cuda_op_fwht(ggml_backend_cuda_context & ctx, const ggml_tensor * src, ggml_tensor * dst);

ggml/src/ggml-cuda/ggml-cuda.cu

@@ -24,6 +24,7 @@
 #include "ggml-cuda/diagmask.cuh"
 #include "ggml-cuda/diag.cuh"
 #include "ggml-cuda/fattn.cuh"
+#include "ggml-cuda/fwht.cuh"
 #include "ggml-cuda/getrows.cuh"
 #include "ggml-cuda/im2col.cuh"
 #include "ggml-cuda/mmf.cuh"
@@ -2594,6 +2595,13 @@ static void ggml_cuda_mul_mat(ggml_backend_cuda_context & ctx, const ggml_tensor
     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;
 
+    const int32_t hint = ggml_get_op_params_i32(dst, 1);
+    if (hint == GGML_HINT_SRC0_IS_HADAMARD) {
+        GGML_ASSERT(!split);
+        ggml_cuda_op_fwht(ctx, src1, dst);
+        return;
+    }
+
     if (!split && use_mul_mat_vec_f) {
         // 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)

tests/test-backend-ops.cpp

@@ -8308,6 +8308,7 @@ static std::vector<std::unique_ptr<test_case>> make_test_cases_eval() {
     test_cases.emplace_back(new test_mul_mat_hadamard(GGML_TYPE_F32, GGML_TYPE_F32, 64, 1, 64));
     test_cases.emplace_back(new test_mul_mat_hadamard(GGML_TYPE_F32, GGML_TYPE_F32, 256, 1, 256));
     test_cases.emplace_back(new test_mul_mat_hadamard(GGML_TYPE_F32, GGML_TYPE_F32, 128, 32, 128));
+    test_cases.emplace_back(new test_mul_mat_hadamard(GGML_TYPE_F32, GGML_TYPE_F32, 128, 4, 128, {2, 3}));
 
 #if 0
     // > 4GB A matrix. Too slow to be enabled by default.