Obviously you didn't read what I posted. The Quantum Transport is compute-intensive physics problem that has a lot of optimization research going behind it. One

Obviously you didn't read what I posted. The Quantum Transport is compute-intensive physics problem that has a lot of optimization research going behind it. One of the main bottleneck to solve this problem is Strided Matrix Multiplication. There is no C vs C++ issue, you keep saying that constexpr and template metaprogramming matter in high performance computing and GPGPU, I have given you links, benchmarks and actual code that showed you that what makes a difference is memory locality. Ergo, as long as your language is low-level enough to control that locality, be it C, C++, Fortran, Rust, Nim, Zig, ... you can achieve speedups by several order of magnitude and it is absolutely required to get high-performance. Constexpr and template metaprogramming don't matter in high performance computing, prove me wrong, walk the talk, don't drink the kool-aid. There are plenty of well studied computation kernels you can use: matrix multiplication, convolution, ray-tracing, recurrent neural network, laplacian, video encoding, Cholesky decomposition, Gaussian filter, Jacobi, Heat, Gauss Seidel, ...