extern "C" __global__ void weno5_lf_flux( const double* __restrict__ cons, double* __restrict__ flux, double alpha, int N) { __shared__ double s[256 + 2 * 5]; int tid = threadIdx.x; int i = blockIdx.x * blockDim.x + tid; // load tile + 5-cell halo s[tid + 5] = cons[min(i, N-1)]; if (tid < 5) { s[tid] = cons[max(i-5, 0)]; s[tid+261] = cons[min(i+256, N-1)]; } __syncthreads(); // WENO5-JS smoothness indicators double b0, b1, b2, w0, w1, w2; weno5_weights(s + tid, &b0, &b1, &b2); // Lax-Friedrichs split + reconstruct flux[i] = lf_split(w0, w1, w2, alpha); }