sdr-wideband-suite/internal/demod/gpudemod/README.md

gpudemod

Phase 1 CUDA demod scaffolding.

Current state

• Standard Go builds use gpudemod_stub.go (!cufft).
• cufft builds allocate GPU buffers and cross the CGO/CUDA launch boundary.
• If CUDA launch wrappers are not backed by compiled kernels yet, the code falls back to CPU DSP.
• The shifted IQ path is already wired so a successful GPU freq-shift result can be copied back and reused immediately.

First real kernel

kernels.cu contains the first candidate implementation:

• gpud_freq_shift_kernel

This is not compiled automatically yet in the current environment because the machine currently lacks a CUDA compiler toolchain in PATH (nvcc not found).

Next machine-side step

On a CUDA-capable dev machine with toolchain installed:

1. Compile kernels.cu into an object file and archive it into a linkable library
   • helper script: tools/build-gpudemod-kernel.ps1
2. For MinGW/CGO builds, prefer building the archive with MinGW host compiler + ar.exe
3. Link gpudemod_kernels.lib into the cufft build
4. Replace gpud_launch_freq_shift(...) stub body with the real kernel launch
5. Validate copied-back shifted IQ against dsp.FreqShift
6. Only then move the next stage (FM discriminator) onto the GPU

Why this is still useful

The runtime/buffer/recorder/fallback structure is already in place, so once kernel compilation is available, real acceleration can be inserted without another architecture rewrite.