private void cftf040(float[] a, int offa) {
        float x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;

        x0r = a[offa] + a[offa + 4];
        x0i = a[offa + 1] + a[offa + 5];
        x1r = a[offa] - a[offa + 4];
        x1i = a[offa + 1] - a[offa + 5];
        x2r = a[offa + 2] + a[offa + 6];
        x2i = a[offa + 3] + a[offa + 7];
        x3r = a[offa + 2] - a[offa + 6];
        x3i = a[offa + 3] - a[offa + 7];
        a[offa] = x0r + x2r;
        a[offa + 1] = x0i + x2i;
        a[offa + 2] = x1r - x3i;
        a[offa + 3] = x1i + x3r;
        a[offa + 4] = x0r - x2r;
        a[offa + 5] = x0i - x2i;
        a[offa + 6] = x1r + x3i;
        a[offa + 7] = x1i - x3r;
    }