feat: CUTLASS Cu10 grouped GEMM — real device verified

BI-V100 real device results:
  moe_group_gemm: err=0.000015 PASS
  moe_decode_cutlass: NaN=False PASS
  cutlass grouped: 4.77ms vs torch.mm loop: 9.38ms → 1.97x speedup

Fix: gemm_grouped.cu ldb=K (not N) for ColumnMajor B view
Link: -lcuinfer from /usr/local/corex-3.2.3/lib64/libcuinfer.so.7

ex_engine/build_gemm_grouped.sh

@@ -0,0 +1,80 @@
+#!/usr/bin/env bash
+# build_gemm_grouped.sh — Compile grouped GEMM kernel + bindings
+#
+# Requires: corex clang/16 + cutlass headers (on BI-V100 device)
+# Output: gemm_grouped.so (importable from Python)
+#
+# Reference: ex_engine/xllm_kernels/build_test_cutlass_batched.sh
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# Source files
+GEMM_CU="${SCRIPT_DIR}/csrc/gemm_grouped.cu"
+BIND_CPP="${SCRIPT_DIR}/csrc/gemm_grouped_bind.cpp"
+BATCHED_CU="${SCRIPT_DIR}/../xllm_kernels/cuda/corex_batched_gemm_kernel.cu"
+
+echo "[gemm] Building gemm_grouped.so"
+
+# Find cutlass include path
+SAMPLES="/usr/local/corex-samples-3.2.3_x86_64/samples/cutlass"
+CUTLASS_INCLUDE=""
+for d in "${SAMPLES}/include" "/usr/local/corex/include/cutlass" "/usr/include/cutlass"; do
+    if [[ -d "$d" ]]; then
+        CUTLASS_INCLUDE="$d"
+        break
+    fi
+done
+
+if [[ -z "$CUTLASS_INCLUDE" ]]; then
+    echo "[gemm] ERROR: cutlass include not found"
+    exit 1
+fi
+echo "[gemm] cutlass: ${CUTLASS_INCLUDE}"
+
+python3 << PYEOF
+import os, sys, shutil
+
+script_dir = "${SCRIPT_DIR}"
+cutlass_inc = "${CUTLASS_INCLUDE}"
+
+sources = [
+    "${GEMM_CU}",
+    "${BIND_CPP}",
+    "${BATCHED_CU}",
+]
+sources = [s for s in sources if os.path.isfile(s)]
+
+print(f"[gemm] Compiling {len(sources)} source files")
+for s in sources:
+    print(f"  {os.path.basename(s)}")
+
+try:
+    from torch.utils.cpp_extension import load
+    mod = load(
+        name="gemm_grouped",
+        sources=sources,
+        extra_include_paths=[cutlass_inc, script_dir],
+        extra_cflags=["-O2", "-std=c++17"],
+        extra_ldflags=["/usr/local/corex/lib64/libcuinfer.so", "-Wl,-rpath,/usr/local/corex/lib64"],
+        extra_cuda_cflags=["-O2", "",
+                           f"-I{cutlass_inc}"],
+        verbose=True,
+    )
+    print("[gemm] ✓ Compilation successful")
+
+    import importlib
+    spec = importlib.util.find_spec("gemm_grouped")
+    if spec and spec.origin:
+        dst = os.path.join(script_dir, "gemm_grouped.so")
+        shutil.copy2(spec.origin, dst)
+        print(f"[gemm] ✓ Saved to {dst}")
+
+except Exception as e:
+    print(f"[gemm] ERROR: {e}", file=sys.stderr)
+    import traceback; traceback.print_exc()
+    sys.exit(1)
+PYEOF
+
+echo "[gemm] Done"