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#include "Halide.h"
using namespace Halide;
extern "C" HALIDE_EXPORT_SYMBOL int expensive(int x) {
float f = 3.0f;
for (int i = 0; i < (1 << 10); i++) {
f = sqrtf(sinf(cosf(f)));
}
if (f < 0) return 3;
return x;
}
HalideExtern_1(int, expensive, int);
int main(int argc, char **argv) {
if (get_jit_target_from_environment().arch == Target::WebAssembly) {
printf("[SKIP] WebAssembly does not support async() yet.\n");
return 0;
}
// Basic compute-root async producer
{
Func producer, consumer;
Var x, y;
producer(x, y) = x + y;
consumer(x, y) = expensive(producer(x - 1, y - 1) + producer(x + 1, y + 1));
consumer.compute_root();
producer.compute_root().async();
Buffer<int> out = consumer.realize({16, 16});
out.for_each_element([&](int x, int y) {
int correct = 2 * (x + y);
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Sliding and folding over a single variable
{
Func producer, consumer;
Var x, y;
producer(x) = expensive(x);
consumer(x) = expensive(producer(x) + producer(x - 1));
consumer.compute_root();
producer.store_root().fold_storage(x, 8).compute_at(consumer, x).async();
Buffer<int> out = consumer.realize({16});
out.for_each_element([&](int x) {
int correct = 2 * x - 1;
if (out(x) != correct) {
printf("out(%d) = %d instead of %d\n",
x, out(x), correct);
exit(1);
}
});
}
// Sliding and folding over a single variable, but flipped
{
Func producer, consumer;
Var x, y;
producer(x) = expensive(x);
consumer(x) = expensive(producer(-x) + producer(-x + 1));
consumer.compute_root();
producer.store_root().fold_storage(x, 8, false).compute_at(consumer, x).async();
Buffer<int> out = consumer.realize({16});
out.for_each_element([&](int x) {
int correct = -2 * x + 1;
if (out(x) != correct) {
printf("out(%d) = %d instead of %d\n",
x, out(x), correct);
exit(1);
}
});
}
// Sliding and folding over y
{
Func producer, consumer;
Var x, y;
producer(x, y) = x + y;
consumer(x, y) = expensive(producer(x - 1, y - 1) + producer(x + 1, y + 1));
consumer.compute_root();
// Producer can run 5 scanlines ahead
producer.store_root().fold_storage(y, 8).compute_at(consumer, y).async();
Buffer<int> out = consumer.realize({16, 16});
out.for_each_element([&](int x, int y) {
int correct = 2 * (x + y);
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Sliding over x and y, folding over y
{
Func producer, consumer;
Var x, y;
producer(x, y) = x + y;
consumer(x, y) = expensive(producer(x - 1, y - 1) + producer(x + 1, y + 1));
consumer.compute_root();
// Producer can still run 5 scanlines ahead
producer.store_root().fold_storage(y, 8).compute_at(consumer, x).async();
Buffer<int> out = consumer.realize({16, 16});
out.for_each_element([&](int x, int y) {
int correct = 2 * (x + y);
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Sliding over x, folding over x and y. Folding over multiple
// dimensions implies separate semaphores for each dimension
// folded to prevent clobbering along each axis. The outer
// semaphore never actually does anything, because the inner
// semaphore stops it from getting that far ahead.
{
Func producer, consumer;
Var x, y;
producer(x, y) = x + y;
// No longer a stencil in y, so that multiple dimensions can be folded
consumer(x, y) = expensive(producer(x - 1, y) + producer(x + 1, y));
consumer.compute_root();
// Producer can run 5 pixels ahead within each scanline, also
// give it some slop in y so it can run ahead to do the first
// few pixels of the next scanline while the producer is still
// chewing on the previous one.
// The producer doesn't run into the new scanline as much as
// it could, because we're sharing one semaphore for x in
// between the two scanlines, so we're a little conservative.
producer.store_root().fold_storage(x, 8).fold_storage(y, 2).compute_at(consumer, x).async();
Buffer<int> out = consumer.realize({16, 16});
out.for_each_element([&](int x, int y) {
int correct = 2 * (x + y);
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Multiple async producers at root.
{
Func producer_1;
Func producer_2;
Func consumer;
Var x, y;
producer_1(x, y) = x;
producer_2(x, y) = y;
// Use different stencils to get different fold factors.
consumer(x, y) = (producer_1(x - 1, y) + producer_1(x + 1, y) +
producer_2(x - 2, y) + producer_2(x + 2, y));
producer_1.compute_root().async();
producer_2.compute_root().async();
Buffer<int> out = consumer.realize({16, 16});
out.for_each_element([&](int x, int y) {
int correct = 2 * (x + y);
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Multiple async producers inside an outer parallel for loop
{
Func producer_1;
Func producer_2;
Func consumer;
Var x, y;
producer_1(x, y) = x;
producer_2(x, y) = y;
consumer(x, y) = (producer_1(x - 1, y) + producer_1(x + 1, y) +
producer_2(x - 2, y) + producer_2(x + 2, y));
producer_1.compute_at(consumer, y).async();
producer_2.compute_at(consumer, y).async();
consumer.parallel(y);
Buffer<int> out = consumer.realize({16, 16});
out.for_each_element([&](int x, int y) {
int correct = 2 * (x + y);
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Multiple async producers inside an outer parallel for loop
// with sliding within the inner serial loop
{
Func producer_1;
Func producer_2;
Func consumer;
Var x, y;
producer_1(x, y) = expensive(x);
producer_2(x, y) = expensive(y);
// Use different stencils to get different fold factors.
consumer(x, y) = expensive((producer_1(x - 1, y) + producer_1(x + 1, y) +
producer_2(x - 2, y) + producer_2(x + 2, y)));
producer_1.compute_at(consumer, x).store_at(consumer, y).async();
producer_2.compute_at(consumer, x).store_at(consumer, y).async();
consumer.parallel(y);
Buffer<int> out = consumer.realize({16, 16});
out.for_each_element([&](int x, int y) {
int correct = 2 * (x + y);
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Nested asynchronous tasks.
{
Func f0, f1, f2;
Var x, y;
f0(x, y) = x + y;
f1(x, y) = f0(x - 1, y - 1) + f0(x + 1, y + 1);
f2(x, y) = f1(x - 1, y - 1) + f1(x + 1, y + 1);
f2.compute_root();
f1.compute_at(f2, y).async();
f0.compute_at(f1, x).async();
Buffer<int> out = f2.realize({16, 16});
out.for_each_element([&](int x, int y) {
int correct = 4 * (x + y);
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Two async producer-consumer pairs over x in a producer-consumer
// relationship over y.
{
Func producer_1;
Func consumer_1;
Func producer_2;
Func consumer_2;
Var x, y;
producer_1(x, y) = x + y;
consumer_1(x, y) = producer_1(x - 1, y) + producer_1(x + 1, y);
producer_2(x, y) = consumer_1(x, y - 1) + consumer_1(x, y + 1);
consumer_2(x, y) = producer_2(x - 1, y) + producer_2(x + 1, y);
consumer_2.compute_root();
producer_2.store_at(consumer_2, y).compute_at(consumer_2, x).async();
consumer_1.store_root().compute_at(consumer_2, y).async();
producer_1.store_at(consumer_2, y).compute_at(consumer_1, x).async();
Buffer<int> out = consumer_2.realize({16, 16});
out.for_each_element([&](int x, int y) {
int correct = 8 * (x + y);
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Sliding and folding over y, with a non-constant amount of stuff
// to acquire/release in the folding semaphore.
{
Func producer, consumer;
Var x, y;
producer(x, y) = x + y;
consumer(x, y) = expensive(producer(x - 1, min(y - 1, 15)) + producer(x + 1, min(y + 1, 17)));
consumer.compute_root();
producer.store_root().fold_storage(y, 8).compute_at(consumer, y).async();
Buffer<int> out = consumer.realize({128, 128});
out.for_each_element([&](int x, int y) {
int correct = (x - 1 + std::min(y - 1, 15)) + (x + 1 + std::min(y + 1, 17));
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Sliding and folding over y, with a non-constant amount of stuff
// to acquire/release in the folding semaphore, and a flip in y
// (the footprint marches monotonically up the image instead of
// monotonically down the image).
{
Func producer, consumer;
Var x, y;
producer(x, y) = x + y;
consumer(x, y) = expensive(producer(x - 1, -min(y - 1, 15)) + producer(x + 1, -min(y + 1, 17)));
consumer.compute_root();
producer.store_root().fold_storage(y, 8, false).compute_at(consumer, y).async();
Buffer<int> out = consumer.realize({128, 128});
out.for_each_element([&](int x, int y) {
int correct = (x - 1 - std::min(y - 1, 15)) + (x + 1 - std::min(y + 1, 17));
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Downsample by 2x in y with sliding and folding over y
{
Func producer, consumer;
Var x, y;
producer(x, y) = x + y;
// Use a lousy [1 1 1 1] downsampling kernel
consumer(x, y) = producer(x, 2 * y - 1) + producer(x, 2 * y) + producer(x, 2 * y + 1) + producer(x, 2 * y + 2);
consumer.compute_root();
producer.store_root().fold_storage(y, 8).compute_at(consumer, y).async();
Buffer<int> out = consumer.realize({16, 64});
out.for_each_element([&](int x, int y) {
int correct = 4 * x + 8 * y + 2;
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Downsample by 1.5x in y with sliding and folding over y
{
Func producer, producer_up, consumer;
Var x, y;
producer(x, y) = x + y;
// Use a dyadic filter equivalent to upsampling by 2x with
// nearest neighbor then downsampling by 3x with a [1 2 3 2 1]
// kernel.
consumer(x, y) = select(y % 2 == 0,
(1 * producer(x, 3 * (y / 2) - 1) +
5 * producer(x, 3 * (y / 2) + 0) +
3 * producer(x, 3 * (y / 2) + 1)),
(3 * producer(x, 3 * (y / 2) + 1) +
5 * producer(x, 3 * (y / 2) + 2) +
1 * producer(x, 3 * (y / 2) + 3)));
consumer.compute_root().align_bounds(y, 2).unroll(y, 2);
producer.store_root().fold_storage(y, 8).compute_at(consumer, y).async();
Buffer<int> out = consumer.realize({256, 256});
out.for_each_element([&](int x, int y) {
// Write it out as a 2x upsample followed by a [1 2 3
// 2 1] downsample to check correctness and also my
// math:
int correct = (9 * x +
((3 * y - 1) >> 1) +
2 * ((3 * y) >> 1) +
3 * ((3 * y + 1) >> 1) +
2 * ((3 * y + 2) >> 1) +
((3 * y + 3) >> 1));
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
// Computing other stages at the outermost var of an async stage
// should include it in the async block.
{
Func producer, producer_friend, consumer;
Var x, y;
producer_friend(x, y) = x + y;
producer(x, y) = x + y + producer_friend(x, y);
consumer(x, y) = producer(x, y);
producer.compute_root().async();
consumer.compute_root();
producer_friend.compute_at(producer, Var::outermost());
Buffer<int> out = consumer.realize({256, 256});
out.for_each_element([&](int x, int y) {
int correct = 2 * (x + y);
if (out(x, y) != correct) {
printf("out(%d, %d) = %d instead of %d\n",
x, y, out(x, y), correct);
exit(1);
}
});
}
printf("Success!\n");
return 0;
}
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