How to define generic reductions using any binary Operator example OR or AND, custom function?

Question

I believe Halide currently supports sum,minimum,maximum and product which work with RDom. I would like to write a function which does reductions over custom binary operations For Eg. 'AND (&&)', 'OR (||)', '(&)', '(|)' etc. How can I do this in Halide ?

Here are my thoughts on this problem: Suppose we have a uint8_t input and to perform a reduction using (|),

RDom rw(0,width); rh(0,height);
Func f,g;
f(y) = cast<uint8_t>(0);
f(y) = f(y) | input(rw,y);
g(x) = cast<uint8_t>(0);
g(x) = g(x) | f(rh);

It would be nice to have a Halide function which can perform generic reduction by means of specifying a reduction function (two inputs)

Thanks in advance for your reply.

score 2 · Accepted Answer · answered Mar 05 '19 at 20:54

The helpers sum, product, etc are not actually built-ins. They are just helpers written in the Halide front-end language itself, so you can define more if you like, or make a generic that takes a binary operator. I would start by looking at https://github.com/halide/Halide/blob/master/src/InlineReductions.cpp

The bulk of the magic is just the automatic capturing of free variables, the rest is just like the code you wrote.

How to define generic reductions using any binary Operator example OR or AND, custom function?

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