// Version:    <1.0>

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////////////////////////////////////////////////////////////////////////////////////////////////////

__kernel void 

advanceintime(

    __global float4 *h0, 

    __global float2 *ht,

    const float twoPiOverWX, 

    const float twoPiOverWY, 

    const int N, 

    const int m,

    const float time)

{

    int i = get_global_id(0);

    int j = get_global_id(1);

    int index = (i << m) + j;

    int mi = (N - i) & (N - 1);

    int mj = (N - j) & (N - 1);

    int indexm = (mi << m) + mj;

    int ii = (i + (N >> 1)) & (N - 1);

    int jj = (j + (N >> 1)) & (N - 1);

    int indexo = (ii << m) + jj;

    int offset = 1 << (2*m);

    float4 hf0Wg1 = h0[index];

    float4 hf0Wg2 = h0[indexm];

    float wt = hf0Wg1.z*time;

    float cs = native_cos(wt);

    float sn = native_sin(wt);

    float2 t1 = (float2)(cs, -sn);

    float2 t2 = (float2)(sn,  cs);

    float2 H1 = (float2)(hf0Wg1.x, hf0Wg1.y);

    float2 H2 = (float2)(hf0Wg2.x, hf0Wg2.y);   

    float hor = dot(H1+H2, t1);

    float hoi = dot(H1-H2, t2);

    float2 h = (float2)(hor, hoi);

    float kx = twoPiOverWX * (i - (N >> 1));

    float ky = twoPiOverWY * (j - (N >> 1));

    float2 h2 = (float2)(h.y, -h.x);

    float4 h3 = (float4)(h2.x*kx, h2.y*kx, h2.x*ky, h2.y*ky);

    ht[indexo] = h;

    ht[indexo + offset] = (float2)(h3.x, h3.y);

    ht[indexo + (offset << 1)] = (float2)(h3.z, h3.w);

}