Function moe_zero_expert_add 

pub fn moe_zero_expert_add(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    out: DevicePtr,
    x: DevicePtr,
    zero_accum: DevicePtr,
    n: u32,
    h: u32,
    stream: u64,
) -> Result<()>

out[t, :] += zero_accum[t] * x[t, :] — the identity-expert blend.