CUTLASS
CUTLASS is a C++ template library for building GEMM (and convolution) kernels with cuBLAS-class performance out of composable, reusable pieces — tile shapes, memory-movement stages, and epilogues — rather than a single pre-built call. cuBLAS is fast but fixed: cublasSgemm computes C = alpha op(A) op(B) + beta * C and nothing else, in the layouts and precisions it was built for. CUTLASS exists for the shapes and fusions that fall outside that fixed surface — an unusual data type, a custom epilogue, a problem size cuBLAS's kernel selection handles badly — while still generating code tuned close to cuBLAS's own throughput on the same hardware.