diff --git a/python/examples/tutorials/mat_mul.py b/python/examples/tutorials/mat_mul.py
index 75650a6cb..bc0017f23 100644
--- a/python/examples/tutorials/mat_mul.py
+++ b/python/examples/tutorials/mat_mul.py
@@ -3,34 +3,79 @@ import triton
 
 class _dot(torch.autograd.Function):
     src = """
-    __global__ void dot(TYPE *A, TYPE *B, TYPE *C, int M, int N, int K,
-                        int lda __multipleof(8), int ldb __multipleof(8), int ldc __multipleof(8)) {
-        int pm = get_program_id(0);
-        int pn = get_program_id(1);
+    __global__ void dot(TYPE *A __noalias __readonly __aligned(16), 
+                        TYPE *B __noalias __readonly __aligned(16), 
+                        TYPE *C __noalias __aligned(16), 
+                        float alpha,
+                        int M, int N, int K,
+                        int lda __multipleof(8), 
+                        int ldb __multipleof(8), 
+                        int ldc __multipleof(8)) {
+      // prologue
+      int ridx = get_program_id(0);
+      int ridy = get_program_id(1);
+      int ridz = get_program_id(2);
+      int gridx = M / TM;
+      int gridy = N / TN;
+      int rid = ridx + ridy * gridx;
+      ridx = rid / gridy;
+      ridy = rid % gridy;
+      int rm[TM] = ridx * TM + 0 ... TM;
+      int rn[TN] = ridy * TN + 0 ... TN;
 
-        // ranges
-        int rm[TM] = pm * TM + 0 ... TM;
-        int rn[TN] = pn * TN + 0 ... TN;
-        int rk[TK] = 0 ... TK;
+      // reduction splitting
+      K           = K / TZ;
+      int rk[TK]  = ridz * K + 0 ... TK;
 
-        // accumulator
-        float c[TM, TN] = 0;
+      // pointers to operands
+      int offa[TM, TK] = rk[newaxis, :] * STRIDE_AK + rm[:, newaxis] * STRIDE_AM;
+      int offb[TK, TN] = rk[:, newaxis] * STRIDE_BK + rn[newaxis, :] * STRIDE_BN;
+      TYPE* pa[TM, TK] = A + offa;
+      TYPE* pb[TK, TN] = B + offb;
 
-        // pointers
-        TYPE* pa[TM, TK] = A + rk[newaxis, :] * 1 + rm[:, newaxis] * lda;
-        TYPE* pb[TK, TN] = B + rk[:, newaxis] * ldb + rn[newaxis, :] * 1;
+      // prefetches operands
+      bool checka[TM, TK] = rk[newaxis, :] < K;
+      bool checkb[TK, TN] = rk[:, newaxis] < K;
+      TYPE a[TM, TK] = checka ? *pa : 0;
+      TYPE b[TK, TN] = checkb ? *pb : 0;
 
-        for(int k=K; k>0; k-=TK) {
-            TYPE a[TM, TK] = *pa;
-            TYPE b[TK, TN] = *pb;
-            c += a @ b;
-            pa = pa + TK * 1;
-            pb = pb + TK * ldb;
-        }
+      // reduction loop
+      float acc[TM, TN] = 0;
+      for(int k = K; k > 0; k -= TK){
+        acc += a @ b;
+        bool checka[TM, TK] = k > TK;
+        bool checkb[TK, TN] = k > TK;
+        pa += TK * STRIDE_AK;
+        pb += TK * STRIDE_BK;
+        a = *?(checka)pa;
+        b = *?(checkb)pb;
+      }
+      acc = acc * alpha;
+      TYPE c[TM, TN] = acc;
 
-        TYPE* pc[TM,TN] = C + rn[newaxis, :] + rm[:,newaxis] * ldc;
-        *pc = c;
-    }
+      // epilogue
+      int rxm[TM] = get_program_id(0) * TM + 0 ... TM;
+      int rxn[TN] = get_program_id(1) * TN + 0 ... TN;
+      int offc[TM, TN] = rxm[:, newaxis] * ldc + rxn[newaxis, :];
+      TYPE* pc[TM, TN] = C + offc;
+      bool checkc[TM, TN] = (rxm[:, newaxis] < M) && (rxn[newaxis, :] < N);
+
+#if (TZ==1)
+      *?(checkc) pc = c;
+#else
+      // accumulate partial result using spin-locks
+      int *plock  = locks + rid;
+      int *pcount = plock + get_num_programs(0) * get_num_programs(1);
+      for(int repeat = 1; repeat == 1; repeat = atomic_cas(plock, 0, 1));
+      int count = *pcount;
+      if(count == 0)
+        *?(checkc) pc = c;
+      else
+        *?(checkc) pc = c + *?(checkc)pc;
+      atomic_xchg(pcount, (count + 1) % TZ);
+      atomic_xchg(plock, 0);
+#endif
+}
     """
 
     @staticmethod
@@ -43,30 +88,31 @@ class _dot(torch.autograd.Function):
 
     @staticmethod
     def _call(a, b):
-        # shapes
-        M, K = a.shape
-        K, N = b.shape
-        # leading dimension
-        lda = K
-        ldb = N
-        ldc = N
-        dtype = a.dtype
         # create kernel if necessary
+        dtype = a.dtype
         if dtype not in _dot.kernel:
             defines = {
                 'TYPE' : dtype,
+                'STRIDE_AM': '1', 'STRIDE_AK': 'lda',
+                'STRIDE_BN': '1', 'STRIDE_BK': 'ldb',
                 'TM'   : [64, 128],
                 'TN'   : [64, 128],
                 'TK'   : [8, 16],
+                'TZ'   : [1]
             }
-            _dot.kernel[dtype] = triton.kernel(_dot.src, num_warps=[2, 4], defines=defines)
+            _dot.kernel[dtype] = triton.kernel(_dot.src, num_warps=[4], defines=defines)
         kernel = _dot.kernel[dtype]
         # allocate output
+        M, K = a.shape
+        K, N = b.shape
         c = triton.empty([M,N], dtype=dtype)
         # enqueue
         grid = lambda opt: [triton.cdiv(M, opt.d('TM')), 
                             triton.cdiv(N, opt.d('TN'))]
-        kernel(a, b, c, M, N, K, lda, ldb, ldc, grid=grid)
+        time = kernel(a, b, c, 1., M, N, K, 
+                      a.stride(0), b.stride(0), c.stride(0), 
+                      grid=grid, bench=100)
+        print(time)
         return c
 
 
@@ -74,12 +120,12 @@ dot = _dot.apply
 
 torch.manual_seed(0)
 
-M, N, K = 128, 512, 256
+M, N, K = 2048, 2048, 2048
 a = torch.rand((M, K)).cuda()
 b = torch.rand((K, N)).cuda()
 
 
-zc  = torch.matmul(a,b)
+#zc  = torch.matmul(a,b)
 zc_ = dot(a,b)
 
-print(torch.allclose(zc, zc_))
\ No newline at end of file
+#print(torch.allclose(zc, zc_))
\ No newline at end of file