WOLFRAM

Wolfram Language & System Documentation Center

Automatic Single- to Double-Precision Conversion

Write code that will use the maximum available precision on the specific CUDA or OpenCL device.

    
First, define the OpenCL code to build the Julia set fractal:
Wolfram Language code: code = " #ifdef USING_DOUBLE_PRECISIONQ #pragma OPENCL EXTENSION cl_khr_fp64 : enable #pragma OPENCL EXTENSION cl_amd_fp64 : enable #endif /* USING_DOUBLE_PRECISIONQ */ __kernel void julia_kernel(__global Real_t * set, int width, int height, Real_t cx, Real_t cy) { int xIndex = get_global_id(0); int yIndex = get_global_id(1); int ii; Real_t x = ZOOM_LEVEL*(width/2 - xIndex); Real_t y = ZOOM_LEVEL*(height/2 - yIndex); Real_t tmp; Real_t c; if (xIndex < width && yIndex < height) { for (ii = 0; ii < MAX_ITERATIONS && x*x + y*y < BAILOUT; ii++) { tmp = x*x - y*y + cx; y = 2*x*y + cy; x = tmp; } c = log(0.1f + sqrt(x*x + y*y)); set[xIndex + yIndex*width] = c; } } ";
Compile and link the OpenCL code automatically in the Wolfram Language:
Wolfram Language code: Needs["OpenCLLink`"] {width, height} = {512, 512}; jset = OpenCLMemoryAllocate[Real, {height, width}]; JuliaCalculate = OpenCLFunctionLoad[code, "julia_kernel", {{_Real, _, "Output"}, _Integer, _Integer, _Real, _Real}, {16, 16}, "Defines" -> {"MAX_ITERATIONS" -> 10, "ZOOM_LEVEL" -> "0.0050", "BAILOUT" -> "4.0"}];
Now you can build the interactive interface to dynamically call the OpenCL code:
Wolfram Language code: Manipulate[ JuliaCalculate[jset, width, height, c[[1]], c[[2]], {width, height}]; ReliefPlot[OpenCLMemoryGet[jset], DataRange -> {{-2.0, 2.0}, {-2.0, 2.0}}, ImageSize -> 256, ColorFunction -> "SunsetColors"], {{c, {0, 1}}, {-2, -2}, {2, 2}, Locator}]