From 869460a932f0c202d06eae66849f71753ac42958 Mon Sep 17 00:00:00 2001
From: biondizzle <biondizzle@gmail.com>
Date: Thu, 28 May 2026 23:54:30 +0000
Subject: [PATCH] debug: add LSE verification and merge debug prints

---
 tests/unit/test_fmha_6warp_multirow.cu | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tests/unit/test_fmha_6warp_multirow.cu b/tests/unit/test_fmha_6warp_multirow.cu
index 5539b9dc..b6afcd38 100644
--- a/tests/unit/test_fmha_6warp_multirow.cu
+++ b/tests/unit/test_fmha_6warp_multirow.cu
@@ -144,6 +144,9 @@ static int test_single(int T, int n_h = 1, int batch = 1) {
                 cs /= (sqrtf(na)*sqrtf(nb)+1e-10f);
                 if(cs<min_cos) min_cos=cs;
                 if(cs<0.999f) { printf("  FAIL b=%d h=%d t=%d cos=%.6f\n",b,h,t,cs); failed++; }
+                // Check LSE
+                float lse_err = fabsf(h_lse[idx*T+t] - lse_ref[t]);
+                if(lse_err > 0.01f) { printf("  FAIL LSE b=%d h=%d t=%d kernel=%.6f ref=%.6f err=%.6f\n",b,h,t,h_lse[idx*T+t],lse_ref[t],lse_err); failed++; }
             }
         }
     }
@@ -218,6 +221,13 @@ static int test_multitile_merge(int T) {
         free(h_o_tile);
     }
 
+    // Debug: print first LSE values per tile
+    for (int tile = 0; tile < N_TILES; tile++) {
+        printf("  tile %d lse[0]=%.6f", tile, lse_per_tile[tile * T]);
+        if (T > 1) printf(" lse[1]=%.6f", lse_per_tile[tile * T + 1]);
+        printf("\n");
+    }
+
     // Python KV merge with normalized O + LSE:
     // O = Σ exp(lse_i - L) * O_i_norm / Σ exp(lse_i - L)
     // where L = max(lse_i) for numerical stability