==== parent kernel ====
printf("s before: %f - ",s[i].x);
mixer <<<1, 64>>>(s, refexp, i);
printf("s after: %f\n", s[i].x);

==== mixer kernel ====
__global__ void mixer(cuFloatComplex *s, float freq, uint32_t i) {
    [....]
    s[i+threadIdx.x].x = t.x;
    s[i+threadIdx.x].y = t.y;
}