Initial release

engine/ggml/src/ggml-cuda/topk-moe.cu

@@ -0,0 +1,418 @@
+#include "ggml-cuda/common.cuh"
+#include "ggml.h"
+#include "topk-moe.cuh"
+
+#include <cmath>
+#include <initializer_list>
+
+// Kernel config struct - passed by value to CUDA kernel
+struct topk_moe_config {
+    bool use_sigmoid;
+    bool with_norm;
+    bool delayed_softmax;
+};
+
+// Warp-local softmax used for both the pre-top-k logits and the post-top-k delayed path.
+template <int experts_per_thread, bool use_limit>
+__device__ void softmax_warp_inplace(float (&vals)[experts_per_thread], const int limit, const int lane) {
+    float max_val = -INFINITY;
+
+#pragma unroll
+    for (int i = 0; i < experts_per_thread; i++) {
+        const int  idx    = lane + i * WARP_SIZE;
+        const bool active = !use_limit || (idx < limit);
+        if (active) {
+            max_val = max(max_val, vals[i]);
+        }
+    }
+
+    max_val = warp_reduce_max(max_val);
+
+    float sum = 0.f;
+
+#pragma unroll
+    for (int i = 0; i < experts_per_thread; i++) {
+        const int  idx    = lane + i * WARP_SIZE;
+        const bool active = !use_limit || (idx < limit);
+        if (active) {
+            const float val = expf(vals[i] - max_val);
+            vals[i]         = val;
+            sum += val;
+        } else {
+            vals[i] = 0.f;
+        }
+    }
+
+    sum = warp_reduce_sum(sum);
+
+    const float inv_sum = 1.0f / sum;
+
+#pragma unroll
+    for (int i = 0; i < experts_per_thread; i++) {
+        const int  idx    = lane + i * WARP_SIZE;
+        const bool active = !use_limit || (idx < limit);
+        if (active) {
+            vals[i] *= inv_sum;
+        }
+    }
+}
+
+template <int experts_per_thread, bool use_limit>
+__device__ void sigmoid_warp_inplace(float (&vals)[experts_per_thread], const int limit, const int lane) {
+#pragma unroll
+    for (int i = 0; i < experts_per_thread; i++) {
+        const int  idx    = lane + i * WARP_SIZE;
+        const bool active = !use_limit || (idx < limit);
+        vals[i]           = active ? 1.f / (1.f + expf(-vals[i])) : -INFINITY;
+    }
+}
+
+/*
+    This kernel does the following:
+    1. optionally softmax over the logits per token [n_experts, n_tokens]
+    2. argmax reduce over the top-k (n_experts_used) logits
+    3. write weights + ids to global memory
+    4. optionally normalize the weights or apply softmax over the selected logits
+
+    It is intended as fusion of softmax->top-k->get_rows pipeline for MoE models
+*/
+template <int n_experts, bool has_bias>
+__launch_bounds__(4 * WARP_SIZE, 1) __global__ void topk_moe_cuda(const float *         logits,
+                                                                  float *               weights,
+                                                                  int32_t *             ids,
+                                                                  float *               bias,
+                                                                  const int             n_rows,
+                                                                  const int             n_expert_used,
+                                                                  const float           clamp_val,
+                                                                  const float           scale_val,
+                                                                  const topk_moe_config config) {
+    const int row = blockIdx.x * blockDim.y + threadIdx.y;
+    if (row >= n_rows) {
+        return;
+    }
+
+    logits += n_experts * row;
+    weights += n_expert_used * row;
+    ids += n_experts * row;
+
+    constexpr int experts_per_thread = (n_experts > WARP_SIZE) ? n_experts / WARP_SIZE : 1;
+
+    float wt[experts_per_thread];
+
+    // Initialize all slots to -INFINITY
+#pragma unroll
+    for (int i = 0; i < experts_per_thread; i++) {
+        wt[i] = -INFINITY;
+    }
+
+    ggml_cuda_pdl_sync();
+#pragma unroll
+    for (int i = 0; i < n_experts; i += WARP_SIZE) {
+        const int expert  = i + threadIdx.x;
+        wt[i / WARP_SIZE] = (n_experts % WARP_SIZE == 0 || expert < n_experts) ? logits[expert] : -INFINITY;
+    }
+
+    if (!config.delayed_softmax) {
+        if (config.use_sigmoid) {
+           sigmoid_warp_inplace<experts_per_thread, false>(wt, n_experts, threadIdx.x);
+        } else {
+           softmax_warp_inplace<experts_per_thread, false>(wt, n_experts, threadIdx.x);
+        }
+    }
+
+    // Sanitize NaN to -FLT_MAX so the iterative argmax produces unique expert IDs.
+    // NaN comparisons always return false, which would cause the same expert to be
+    // selected repeatedly. -FLT_MAX compares normally and is still excluded by the
+    // -INFINITY sentinel used after each selection round.
+    // More relevant for the cuBLAS path. See https://github.com/ggml-org/llama.cpp/issues/19659
+#pragma unroll
+    for (int i = 0; i < experts_per_thread; i++) {
+        if (__isnanf(wt[i])) {
+            wt[i] = -FLT_MAX;
+        }
+    }
+
+    // selection_wt is only needed when bias is present (selection uses wt + bias)
+    // when no bias, we use wt directly for both selection and weight values
+    [[maybe_unused]] float selection_wt[has_bias ? experts_per_thread : 1];
+
+    if constexpr (has_bias) {
+#pragma unroll
+        for (int i = 0; i < experts_per_thread; i++) {
+            selection_wt[i] = -INFINITY;
+        }
+#pragma unroll
+        for (int i = 0; i < n_experts; i += WARP_SIZE) {
+            const int expert = i + threadIdx.x;
+            selection_wt[i / WARP_SIZE] =
+                (n_experts % WARP_SIZE == 0 || expert < n_experts) ? wt[i / WARP_SIZE] + bias[expert] : -INFINITY;
+        }
+    }
+
+    //at this point, each thread holds either a portion of the softmax distribution
+    //or the raw logits. We do the argmax reduce over n_expert_used, each time marking
+    //the expert weight as -inf to exclude from the next iteration
+
+    float wt_sum = 0.f;
+
+    float output_weights[experts_per_thread];
+
+#pragma unroll
+    for (int i = 0; i < experts_per_thread; i++) {
+        output_weights[i] = 0.f;
+    }
+
+    ggml_cuda_pdl_lc();
+    for (int k = 0; k < n_expert_used; k++) {
+        float max_val    = wt[0];
+        int   max_expert = threadIdx.x;
+
+        if constexpr (has_bias) {
+            float max_val_s = selection_wt[0];
+
+#pragma unroll
+            for (int i = 1; i < experts_per_thread; i++) {
+                const int expert = threadIdx.x + i * WARP_SIZE;
+                if ((n_experts % WARP_SIZE == 0 || expert < n_experts) && selection_wt[i] > max_val_s) {
+                    max_val    = wt[i];
+                    max_val_s  = selection_wt[i];
+                    max_expert = expert;
+                }
+            }
+
+#pragma unroll
+            for (int mask = WARP_SIZE / 2; mask > 0; mask /= 2) {
+                const float val    = __shfl_xor_sync(0xFFFFFFFF, max_val, mask, WARP_SIZE);
+                const float val_s  = __shfl_xor_sync(0xFFFFFFFF, max_val_s, mask, WARP_SIZE);
+                const int   expert = __shfl_xor_sync(0xFFFFFFFF, max_expert, mask, WARP_SIZE);
+                if (val_s > max_val_s || (val_s == max_val_s && expert < max_expert)) {
+                    max_val    = val;
+                    max_val_s  = val_s;
+                    max_expert = expert;
+                }
+            }
+
+            if ((max_expert & (WARP_SIZE - 1)) == threadIdx.x) {
+                selection_wt[max_expert / WARP_SIZE] = -INFINITY;
+            }
+        } else {
+#pragma unroll
+            for (int i = 1; i < experts_per_thread; i++) {
+                const int expert = threadIdx.x + i * WARP_SIZE;
+                if ((n_experts % WARP_SIZE == 0 || expert < n_experts) && wt[i] > max_val) {
+                    max_val    = wt[i];
+                    max_expert = expert;
+                }
+            }
+
+#pragma unroll
+            for (int mask = WARP_SIZE / 2; mask > 0; mask /= 2) {
+                const float val    = __shfl_xor_sync(0xFFFFFFFF, max_val, mask, WARP_SIZE);
+                const int   expert = __shfl_xor_sync(0xFFFFFFFF, max_expert, mask, WARP_SIZE);
+                if (val > max_val || (val == max_val && expert < max_expert)) {
+                    max_val    = val;
+                    max_expert = expert;
+                }
+            }
+
+            if ((max_expert & (WARP_SIZE - 1)) == threadIdx.x) {
+                wt[max_expert / WARP_SIZE] = -INFINITY;
+            }
+        }
+
+        if ((k & (WARP_SIZE - 1)) == threadIdx.x) {
+            output_weights[k / WARP_SIZE] = max_val;
+        }
+
+        if ((max_expert & (WARP_SIZE - 1)) == threadIdx.x) {
+            ids[k] = max_expert;
+            if (config.with_norm) {
+                wt_sum += max_val;
+            }
+        }
+    }
+
+    if (config.with_norm) {
+        wt_sum              = warp_reduce_sum(wt_sum);
+        wt_sum              = max(wt_sum, clamp_val);
+        const float inv_sum = 1.0f / wt_sum;
+
+        for (int i = 0; i < experts_per_thread; i++) {
+            output_weights[i] *= inv_sum;
+        }
+    }
+
+    if (config.delayed_softmax) {
+        softmax_warp_inplace<experts_per_thread, true>(output_weights, n_expert_used, threadIdx.x);
+    }
+
+#pragma unroll
+    for (int i = 0; i < experts_per_thread; i++) {
+        const int idx = i * WARP_SIZE + threadIdx.x;
+        if (idx < n_expert_used) {
+            weights[idx] = output_weights[i] * scale_val;
+        }
+    }
+}
+
+template<bool has_bias>
+static void launch_topk_moe_cuda(ggml_backend_cuda_context & ctx,
+                                 const float *               logits,
+                                 float *                     weights,
+                                 int32_t *                   ids,
+                                 float *                     bias,
+                                 const int                   n_rows,
+                                 const int                   n_expert,
+                                 const int                   n_expert_used,
+                                 const float                 clamp_val,
+                                 const float                 scale_val,
+                                 const topk_moe_config       config) {
+    GGML_ASSERT(!(config.with_norm && config.delayed_softmax) &&
+                "delayed softmax is not supported with weight normalization");
+    const int    rows_per_block = 4;
+    dim3         grid_dims((n_rows + rows_per_block - 1) / rows_per_block, 1, 1);
+    dim3         block_dims(WARP_SIZE, rows_per_block, 1);
+    cudaStream_t stream = ctx.stream();
+    const ggml_cuda_kernel_launch_params launch_params = ggml_cuda_kernel_launch_params(grid_dims, block_dims, 0, stream);
+
+    switch (n_expert) {
+        case 1:
+            ggml_cuda_kernel_launch(topk_moe_cuda<1, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        case 2:
+            ggml_cuda_kernel_launch(topk_moe_cuda<2, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        case 4:
+            ggml_cuda_kernel_launch(topk_moe_cuda<4, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        case 8:
+            ggml_cuda_kernel_launch(topk_moe_cuda<8, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        case 16:
+            ggml_cuda_kernel_launch(topk_moe_cuda<16, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        case 32:
+            ggml_cuda_kernel_launch(topk_moe_cuda<32, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        case 64:
+            ggml_cuda_kernel_launch(topk_moe_cuda<64, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        case 128:
+            ggml_cuda_kernel_launch(topk_moe_cuda<128, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        case 256:
+            ggml_cuda_kernel_launch(topk_moe_cuda<256, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        case 512:
+            ggml_cuda_kernel_launch(topk_moe_cuda<512, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        case 576:
+            ggml_cuda_kernel_launch(topk_moe_cuda<576, has_bias>, launch_params,
+                logits, weights, ids, bias, n_rows, n_expert_used, clamp_val, scale_val, config);
+            break;
+        default:
+            GGML_ASSERT(false && "fatal error");
+            break;
+    }
+}
+
+void ggml_cuda_op_topk_moe(ggml_backend_cuda_context &     ctx,
+                           const ggml_tensor *             logits,
+                           ggml_tensor *                   weights,
+                           ggml_tensor *                   ids,
+                           const ggml_tensor *             clamp,
+                           const ggml_tensor *             scale,
+                           const ggml_tensor *             bias,
+                           const ggml_cuda_topk_moe_args & args) {
+    GGML_ASSERT(logits->type == GGML_TYPE_F32);
+    GGML_ASSERT(weights->type == GGML_TYPE_F32);
+    GGML_ASSERT(ids->type == GGML_TYPE_I32);
+
+    const int n_experts = logits->ne[0];
+    const int n_rows    = logits->ne[1];
+
+    const float * logits_d  = (const float *) logits->data;
+    float *       weights_d = (float *) weights->data;
+    int32_t *     ids_d     = (int32_t *) ids->data;
+    float *       bias_d    = bias ? (float *) bias->data : nullptr;
+
+    float scale_val = scale ? ggml_get_op_params_f32(scale, 0) : 1.0f;
+
+    GGML_ASSERT(ids->nb[1] / ggml_type_size(ids->type) == (size_t) n_experts);
+
+    const int n_expert_used = weights->ne[1];
+
+    const bool with_norm = clamp != nullptr;
+
+    float clamp_val = -INFINITY;
+    if (clamp) {
+        clamp_val = ggml_get_op_params_f32(clamp, 0);
+    }
+
+    topk_moe_config config;
+    config.use_sigmoid     = args.sigmoid;
+    config.with_norm       = with_norm;
+    config.delayed_softmax = args.delayed_softmax;
+
+    if (bias) {
+        launch_topk_moe_cuda<true>(ctx, logits_d, weights_d, ids_d, bias_d, n_rows, n_experts, n_expert_used, clamp_val,
+                             scale_val, config);
+    } else {
+        launch_topk_moe_cuda<false>(ctx, logits_d, weights_d, ids_d, bias_d, n_rows, n_experts, n_expert_used, clamp_val,
+                             scale_val, config);
+    }
+}
+
+bool ggml_cuda_should_use_topk_moe(const ggml_tensor * gating_op,
+                                   const ggml_tensor * weights,
+                                   const ggml_tensor * logits,
+                                   const ggml_tensor * ids) {
+    const int n_expert = ids->nb[1] / ids->nb[0];
+    if (((n_expert & (n_expert - 1)) != 0 || n_expert > 512) && n_expert != 576) {
+        return false;
+    }
+
+    if (!ggml_is_contiguous(weights) || !ggml_is_contiguous(logits)) {
+        return false;
+    }
+
+    if (gating_op->op == GGML_OP_SOFT_MAX) {
+        const ggml_tensor * softmax  = gating_op;
+        float               scale    = 1.0f;
+        float               max_bias = 0.0f;
+
+        memcpy(&scale, (const float *) softmax->op_params + 0, sizeof(float));
+        memcpy(&max_bias, (const float *) softmax->op_params + 1, sizeof(float));
+
+        if (!ggml_is_contiguous(softmax->src[0])) {
+            return false;
+        }
+
+        if (scale != 1.0f || max_bias != 0.0f) {
+            return false;
+        }
+
+        // don't fuse when masks or sinks are present
+        if (softmax->src[1] || softmax->src[2]) {
+            return false;
+        }
+    } else if (gating_op->op == GGML_OP_UNARY) {
+        ggml_unary_op op = ggml_get_unary_op(gating_op);
+
+        if (op != GGML_UNARY_OP_SIGMOID) {
+            return false;
+        }
+    }
+
+    return true;
+}