Example of loop unrolling vs default

loop_unrolling.cc

# Without Loop Unrolling
for (int y = 0; y < height; ++y) {
  for (int x = 0; x < width; ++x) {
    for (int c = 0; c < 3; ++c) {
      output(x, y, c) = input(x, y, c) + b;
    }
  }
}

# With Loop Unrolling
for (int y = 0; y < height; ++y) {
  for (int x = 0; x < width; ++x) {
    output(x, y, 0) = input(x, y, 0) + b;
    output(x, y, 1) = input(x, y, 1) + b;
    output(x, y, 2) = input(x, y, 2) + b;
  }
}