text: #include <Halide.h>
  #include <stdio.h>
  
  using namespace Halide;
  
  int main(int argc, char **argv) {
      if (!get_jit_target_from_environment().has_gpu_feature()) {
          printf("No gpu target enabled. Skipping test.\n");
          return 0;
      }
  
      Func f, g, h, out;
      Var x, y, z;
  
      f(x, y, z) = x + y + z;
      f(x, y, z) += 1;
      g(x, y, z) = f(x, y, z);
      g(x, y, z) += 1;
      h(x, y, z) = g(x, y, z);
      h(x, y, z) += 1;
      out(x, y, z) = h(x, y, z);
      out(x, y, z) += 1;
  
      out.gpu_tile(x, y, z, 4, 4, 4);
      out.update().gpu_tile(x, y, 4, 4);
      h.compute_at(out, Var::gpu_blocks()).gpu_threads(x, y);
      h.update().gpu_threads(x);
      // Normally it isn't useful to schedule things at in-between
      // thread levels, so Halide doesn't expose a clean name for it.
      g.compute_at(h, Var("__thread_id_y")).gpu_threads(x);
      g.update();
      f.compute_at(g, Var::gpu_threads());
      f.update();
  
      Image<int> o = out.realize(64, 64, 64);
  
      for (int z = 0; z < 64; z++) {
          for (int y = 0; y < 64; y++) {
              for (int x = 0; x < 64; x++) {
                  int correct = x + y + z + 4;
                  if (o(x, y, z) != correct) {
                      printf("out(%d, %d, %d) = %d instead of %d\n",
                             x, y, z, o(x, y, z), correct);
                      return -1;
                  }
              }
          }
      }
  
      printf("Success!\n");
      return 0;
  }
  