Function sigmoid

cake-core/benches/bench_backend_ops.rs:93–99

(bencher: divan::Bencher, size: usize)

#[divan::bench(args = [256, 1024, 4096])]
fn sigmoid(bencher: divan::Bencher, size: usize) {
    let b = backend();
    let x = Tensor::randn(0f32, 1.0, (1, size), &Device::Cpu).unwrap();
    bencher.bench_local(|| {
        let _ = b.sigmoid(&x).unwrap();
    });
}

// ── embedding ──────────────────────────────────────────────────────────