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inline int offset(int x, int y, int width) { return width*y + x; }
inline float mapX(float x) {return x*3.25f - 2.f;}
inline float mapY(float y) {return y*2.5f - 1.25f;}
__kernel void compiler_mandelbrot_alternate(__global uint *out,
float rcpWidth,
float rcpHeight,
float criterium)
{
int xDim = get_global_id(0);
int yDim = get_global_id(1);
int width = get_global_size(0);
int height = get_global_size(1);
int idx = offset(xDim, yDim, width);
float xOrigin = mapX((float) xDim * rcpWidth);
float yOrigin = mapY((float) yDim * rcpHeight);
float x = 0.0f;
float y = 0.0f;
float iteration = 256.f;
bool breakCond = true;
while (breakCond) {
const float xtemp = mad(-y,y,mad(x,x,xOrigin));
y = mad(2.f*x, y, yOrigin);
x = xtemp;
iteration -= 1.f;
breakCond = -mad(y,y,mad(x,x, -criterium)) * iteration > 0.f;
}
const uint iIteration = 256 - (uint) iteration;
const uint isBlack = (iIteration == 256);
const uint black = 255 << 24;
const uint nonBlack = iIteration | (iIteration << 8) | (iIteration << 16) | (255 << 24);
out[idx] = select(nonBlack, black, isBlack);
}
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