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#!/usr/bin/python3
# Halide tutorial lesson 3
# This lesson demonstrates how to inspect what the Halide compiler is
# producing.
# This lesson can be built by invoking the command:
# make test_tutorial_lesson_03_debugging_1
# in a shell with the current directory at python_bindings/
import halide as hl
def main():
# We'll start by defining the simple single-stage imaging
# pipeline from lesson 1.
# This lesson will be about debugging, but unfortunately in C++,
# objects don't know their own names, which makes it hard for us
# to understand the generated code. To get around this, you can
# pass a string to the hl.Func and hl.Var constructors to give them a
# name for debugging purposes.
gradient = hl.Func("gradient")
x, y = hl.Var("x"), hl.Var("y")
gradient[x, y] = x + y
# Realize the function to produce an output image. We'll keep it
# very small for this lesson.
gradient.realize([8, 8])
# That line compiled and ran the pipeline. Try running this
# lesson with the environment variable HL_DEBUG_CODEGEN set to
# 1. It will print out the various stages of compilation, and a
# pseudocode representation of the final pipeline.
# If you set HL_DEBUG_CODEGEN to a higher number, you can see
# more and more details of how Halide compiles your pipeline.
# Setting HL_DEBUG_CODEGEN=2 shows the Halide code at each stage
# of compilation, and also the llvm bitcode we generate at the
# end.
# Halide will also output an HTML version of this output, which
# supports syntax highlighting and code-folding, so it can be
# nicer to read for large pipelines. Open gradient.stmt.html" with your
# browser after running this tutorial.
gradient.compile_to_lowered_stmt("gradient.stmt.html", [], hl.StmtOutputFormat.HTML)
# You can usually figure out what code Halide is generating using
# this pseudocode. In the next lesson we'll see how to snoop on
# Halide at runtime.
print("Success!")
return 0
if __name__ == "__main__":
main()
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