CUTLASS 2.3 initial commit (#134)

CUTLASS 2.3 adds GEMMs targeting Sparse Tensor Cores on the NVIDIA Ampere Architecture, fast SGEMM, and small matrix classes, bug fixes, and performance enhancements.

test/unit/core/bfloat16.cu

@@ -142,6 +142,9 @@ TEST(bfloat16_t, host_conversion) {
     EXPECT_TRUE(static_cast<float>(y) == f);
   }
 
+  // Try out default-ctor (zero initialization of primitive proxy type)
+  EXPECT_TRUE(cutlass::bfloat16_t() == 0.0_bf16);
+
   // Try out user-defined literals
   EXPECT_TRUE(cutlass::bfloat16_t(7) == 7_bf16);
   EXPECT_TRUE(7 == static_cast<int>(7_bf16));