Minimal GPU example

The following is the simplest program that does something interesting on the GPU. It uses JIT compilation.

#include <Halide.h>
#include <stdio.h>

int main(int argc, char **argv) {
  // Define a gradient function.
  Halide::Func f;
  Halide::Var x, y;
  f(x, y) = x + y;

  // Schedule f on the GPU in 16x16 tiles.
  f.gpu_tile(x, y, 16, 16);

  // Construct a target that uses the GPU.
  Halide::Target target = Halide::get_host_target();

  // Enable OpenCL as the GPU backend.
  target.set_feature(Halide::Target::OpenCL);

  // Enable debugging so that you can see what OpenCL API calls we do.
  target.set_feature(Halide::Target::Debug);

  // JIT-compile the pipeline.
  f.compile_jit(target);

  // Run it.
  Halide::Image<int> result = f.realize(32, 32);

  // Print the result.
  for (int y = 0; y < result.height(); y++) {
      for (int x = 0; x < result.width(); x++) {
          printf("%3d ", result(x, y));
      }
      printf("\n");
  }

  return 0;
}

For a longer worked example of using the GPU, see tutorial lesson 12