Halide - AshokBhat/notes GitHub Wiki

About

• A language for fast, portable computation on images and tensors
• Embedded in C++
• Allows algorithm and implementation details to be separated, making to easier to tune to a platform.

Repository

• https://github.com/halide/Halide
• Aim to release new versions of Halide at the same cadence as LLVM (every six months or so)
• Version number based on LLVM version

Example

Func halide_blur(Func in) f
 Func tmp, blurred;
  Var x, y, xi, yi;

  // The algorithm - No storage or order
  // Defines a simple 3x3 blur filter split into a blur horizontal followed by a blur vertical step

  tmp(x, y) = (in(x-1, y) + in(x, y) + in(x+1, y))/3;
  blurred(x, y) = (tmp(x, y-1) + tmp(x, y) + tmp(x, y+1))/3;

  // The schedule - 
  // Specifies how the algorithm can be treated in a parallel implementation

  blurred.tile(x, y, xi, yi, 256, 32).vectorize(xi, 8).parallel(y);
  tmp.chunk(x).vectorize(x, 8);
 return blurred;
}

FAQ

• What is Halide?
• What is the key innovation?
• Where is it used?
• What does it use for underlying technology?

Users

• Adobe for Photoshop
• Google for Pixel

See also

• LLVM