TorchFDTD: GPU-accelerated finite-difference time-domain simulation with discrete adjoints and host-streamed execution for photonic inverse design

Gradient-based photonic design needs full-wave derivatives with respect to millions of parameters, but on a single GPU workstation the time-domain adjoint is limited by device memory and by the incompatibility of fused update kernels with automatic differentiation. Here, we present TorchFDTD, an ope