Function fractional_sumcheck_gpu 

pub fn fractional_sumcheck_gpu<SC, TS>(
    transcript: &mut TS,
    leaves: DeviceBuffer<Frac<EF>>,
    sizes: FractionalInputSize,
    alpha: EF,
    assert_zero: bool,
    mem: &mut MemTracker,
    device_ctx: &GpuDeviceCtx,
) -> Result<(FracSumcheckProof<SC>, Vec<EF>), FractionalSumcheckError>
where
    SC: StarkProtocolConfig<EF = EF>,
    TS: FiatShamirTranscript<SC>,

GKR fractional sumcheck prover. See docs/cuda-backend/gkr-prover.md (repo root) for the protocol and implementation details.