 __device__ inline float
 gridkernelhat (const float u, const float kernwidth, const float sigma)
 {
-    // u in [-n/2,n/2]
+    // u in [-1/sigma,1/sigma]
     const float J = 2.0f*kernwidth;
     float alpha = kernel_shape(kernwidth, sigma);
     float r = M_PI*J*u;

        z = sqrtf(-q);
        y = J * sinhf(z) / z / besseli0(alpha);
    } else
        y = 0.0f;
    // identity: J_1/2(z) = sin(z) * sqrt(2/pi/z)
    return y;
}

        switch (c) {
            case '3':
                flags.koosh = 1;
                break;
            case 'a':
                flags.adjoint = 1;
                break;
