Minimal PV SS MMA test: A=128x16, B=16x16

2026-05-28 14:23:42 +00:00
parent 77901834a9
commit 4a36da9845
1 changed files with 106 additions and 0 deletions
--- a/tests/unit/test_pv_ss.cu
+++ b/tests/unit/test_pv_ss.cu
@@ -0,0 +1,106 @@
+/**
+ * Minimal test: PV via SS MMA with just 1 K-tile.
+ * P(128,16) × V(16,16) → O(128,16)
+ * A = P K-tile (128, 16) from SMEM, B = V K-tile (16, 16) from SMEM
+ * Both in canonical K-major layout.
+ * Tests if SS MMA can handle BLOCK_MN_A=128, BLOCK_MN_B=16.
+ */
+
+#include <cuda_runtime.h>
+#include <cstdio>
+#include <cmath>
+#include <cstring>
+
+#include "dsv4/kernels/attention/fmha_common.cuh"
+#include "dsv4/kernels/attention/fmha_umma_desc.cuh"
+
+using namespace dsv4::kernels::attention;
+
+static bf16_t f32_to_bf16_host(float f) { uint32_t u; memcpy(&u,&f,4); return (uint16_t)(u>>16); }
+static float bf16_to_f32_host(bf16_t h) { uint32_t u=(uint32_t)h<<16; float f; memcpy(&f,&u,4); return f; }
+
+constexpr int HD = 16, BLOCK_MN = 128;
+
+__global__ void __launch_bounds__(128)
+test_pv_ss()
+{
+    const int tid = threadIdx.x, wid = tid / 32, lane = tid % 32;
+
+    extern __shared__ char sbuf[];
+    uint32_t* sTmemBase = (uint32_t*)sbuf;
+    // A = P (128, 16) canonical — all 1.0 for row 0, 0 elsewhere
+    bf16_t* sP = (bf16_t*)(((uintptr_t)(sbuf + 4) + 15) & ~(uintptr_t)15);
+    // B = V (16, 16) canonical — all 2.0
+    bf16_t* sV = (bf16_t*)(((uintptr_t)(sP + 128 * 16) + 127) & ~(uintptr_t)127);
+
+    // Fill P: (128, 16) canonical, row 0 = all 1.0
+    constexpr int CORES_MN = 128 / 8;  // 16
+    constexpr int CORES_K = 16 / 8;    // 2
+    for (int i = tid; i < 128 * 16; i += 128) sP[i] = 0;
+    __syncthreads();
+    // Row 0: core_mn=0, local_r=0
+    for (int c = tid; c < 16; c += 128) {
+        int ck = c / 8, lc = c % 8;
+        int dst_idx = ck * CORES_MN * 64 + 0 * 64 + 0 * 8 + lc;
+        sP[dst_idx] = f32_to_bf16(1.0f);
+    }
+
+    // Fill V: (16, 16) canonical, all 2.0
+    for (int i = tid; i < 16 * 16; i += 128) sV[i] = 0;
+    __syncthreads();
+    for (int i = tid; i < 16 * 16; i += 128) {
+        int r = i / 16, c = i % 16;
+        int ck = c / 8, lc = c % 8;
+        int tmn = r / 8, lr = r % 8;
+        sV[ck * 2 * 64 + tmn * 64 + lr * 8 + lc] = f32_to_bf16(2.0f);
+    }
+    __syncthreads();
+
+    // TMEM alloc: 128 columns
+    if (wid == 1) tmem_alloc(__cvta_generic_to_shared(sTmemBase), 128);
+    __syncthreads();
+    uint32_t tb = *sTmemBase;
+
+    // PV SS MMA: A=(128,16) BLOCK_MN=128, B=(16,16) BLOCK_MN=16
+    // C = A × B^T = (128, 16) → TMEM
+    // Expected: C[0, 0..15] = 16.0 (1.0 * 2.0 * 8 core values... actually sum of 16 ones * 2.0 = 32.0, MMA scale 0.5 → 16.0)
+    printf("Before PV: tid=%d\n", tid);
+    uint64_t dp = make_umma_desc_kmajor_none(__cvta_generic_to_shared(sP), BLOCK_MN);
+    uint64_t dv = make_umma_desc_kmajor_none(__cvta_generic_to_shared(sV), 16);
+    uint32_t idesc = make_idesc(BLOCK_MN, HD);  // MMA_M=8, MMA_N=1
+    if (tid == 0) umma_ss_f16(tb, dp, dv, idesc, false);
+    asm volatile("tcgen05.fence::after_thread_sync;" ::: "memory");
+    __syncthreads();
+    printf("After PV: tid=%d\n", tid);
+
+    // Read O from TMEM
+    if (wid == 0) {
+        float o_vals[HD];
+        for (int n = 0; n < HD / 8; n++) {
+            float tmp[8];
+            asm volatile("tcgen05.ld.sync.aligned.32x32b.x8.b32 {%0,%1,%2,%3,%4,%5,%6,%7},[%8];"
+                : "=f"(tmp[0]),"=f"(tmp[1]),"=f"(tmp[2]),"=f"(tmp[3]),
+                  "=f"(tmp[4]),"=f"(tmp[5]),"=f"(tmp[6]),"=f"(tmp[7])
+                : "r"(tb + n*8));
+            asm volatile("tcgen05.wait::ld.sync.aligned;");
+            if (lane == 0) for (int c=0;c<8;c++) o_vals[n*8+c] = tmp[c] * 2.0f;
+        }
+        if (lane == 0) {
+            printf("O[0,0..15]: ");
+            for (int d=0;d<HD;d++) printf("%.2f ", o_vals[d]);
+            printf("(expect 16.0)\n");
+        }
+    }
+
+    if (wid == 0) tmem_dealloc(tb, 128);
+}
+
+int main() {
+    printf("=== PV SS MMA Test (A=128x16, B=16x16) ===\n");
+    int smem = (4+16 + 128*16*2 + 16*16*2 + 256 + 127) & ~127;
+    test_pv_ss<<<1, 128, smem>>>();
+    cudaError_t err = cudaDeviceSynchronize();
+    if (err != cudaSuccess) { printf("CUDA ERROR: %s\n", cudaGetErrorString(err)); return 1; }
+    printf("PASS\n");
+    return 0;
+}