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tutorial/lesson_10_aot_compilation_generate.cpp
// Halide tutorial lesson 10: AOT compilation part 1
// This lesson demonstrates how to use Halide as an more traditional
// ahead-of-time (AOT) compiler.
// This lesson is split across two files. The first (this one), builds
// a Halide pipeline and compiles it to a static library and
// header. The second (lesson_10_aot_compilation_run.cpp), uses that
// static library to actually run the pipeline. This means that
// compiling this code is a multi-step process.
// On linux, you can compile and run it like so:
// g++ lesson_10*generate.cpp -g -std=c++17 -I <path/to/Halide.h> -L <path/to/libHalide.so> -lHalide -lpthread -ldl -o lesson_10_generate
// LD_LIBRARY_PATH=<path/to/libHalide.so> ./lesson_10_generate
// g++ lesson_10*run.cpp lesson_10_halide.a -std=c++17 -I <path/to/Halide.h> -lpthread -ldl -o lesson_10_run
// ./lesson_10_run
// On os x:
// g++ lesson_10*generate.cpp -g -std=c++17 -I <path/to/Halide.h> -L <path/to/libHalide.so> -lHalide -o lesson_10_generate
// DYLD_LIBRARY_PATH=<path/to/libHalide.dylib> ./lesson_10_generate
// g++ lesson_10*run.cpp lesson_10_halide.a -o lesson_10_run -I <path/to/Halide.h>
// ./lesson_10_run
// The benefits of this approach are that the final program:
// - Doesn't do any jit compilation at runtime, so it's fast.
// - Doesn't depend on libHalide at all, so it's a small, easy-to-deploy binary.
// If you have the entire Halide source tree, you can also build it by
// running:
// make tutorial_lesson_10_aot_compilation_run
// in a shell with the current directory at the top of the halide
// source tree.
#include "Halide.h"
#include <stdio.h>
using namespace Halide;
int main(int argc, char **argv) {
// We'll define a simple one-stage pipeline:
Func brighter;
Var x, y;
// The pipeline will depend on one scalar parameter.
Param<uint8_t> offset;
// And take one grayscale 8-bit input buffer. The first
// constructor argument gives the type of a pixel, and the second
// specifies the number of dimensions (not the number of
// channels!). For a grayscale image this is two; for a color
// image it's three. Currently, four dimensions is the maximum for
// inputs and outputs.
ImageParam input(type_of<uint8_t>(), 2);
// If we were jit-compiling, these would just be an int and a
// Buffer, but because we want to compile the pipeline once and
// have it work for any value of the parameter, we need to make a
// Param object, which can be used like an Expr, and an ImageParam
// object, which can be used like a Buffer.
// Define the Func.
brighter(x, y) = input(x, y) + offset;
// Schedule it.
brighter.vectorize(x, 16).parallel(y);
// This time, instead of calling brighter.realize(...), which
// would compile and run the pipeline immediately, we'll call a
// method that compiles the pipeline to a static library and header.
//
// For AOT-compiled code, we need to explicitly declare the
// arguments to the routine. This routine takes two. Arguments are
// usually Params or ImageParams.
brighter.compile_to_static_library("lesson_10_halide", {input, offset}, "brighter");
printf("Halide pipeline compiled, but not yet run.\n");
// To continue this lesson, look in the file lesson_10_aot_compilation_run.cpp
return 0;
}
Halide::Func
A halide function.
Definition Func.h:706
Halide::Func::parallel
Func & parallel(const VarOrRVar &var)
Mark a dimension to be traversed in parallel.
Halide::Func::vectorize
Func & vectorize(const VarOrRVar &var)
Mark a dimension to be computed all-at-once as a single vector.
Halide::Func::compile_to_static_library
void compile_to_static_library(const std::string &filename_prefix, const std::vector< Argument > &args, const std::string &fn_name="", const Target &target=get_target_from_environment())
Compile to static-library file and header pair, with the given arguments.
Halide::ImageParam
An Image parameter to a halide pipeline.
Definition ImageParam.h:23
Halide::Param
A scalar parameter to a halide pipeline.
Definition Param.h:22
Halide::Var
A Halide variable, to be used when defining functions.
Definition Var.h:19
Halide
This file defines the class FunctionDAG, which is our representation of a Halide pipeline,...
Definition AbstractGenerator.h:19
Halide::type_of
Type type_of()
Construct the halide equivalent of a C type.
Definition Type.h:572