diku-dk / futhark

:boom::computer::boom: A data-parallel functional programming language
http://futhark-lang.org
ISC License
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C code generation involving large arrays of constants is very slow #2160

Closed athas closed 5 months ago

athas commented 5 months ago

The Futhark compiler can handle large arrays of monomorphic literals reasonably well (due to a specialised fast path). However, when the code generator constructs a C AST via language-c-quote and feeds it to the prettyprinter, it can take a pretty long time. I do not think language-c-quote is designed to handle array literals with that many elements. For a representative program submitted by @WilliamDue, the C backend takes 17s to generate the program, while the Python backend takes 1s - and that is including fairly naive (inefficient) prettyprinting.

I don't know if there is a quick way to hack up a fix, or if we should consider ditching language-c-quote and using a simpler representation for C. We don't need most of what it offers, and we particularly don't need its tracking of source locations (which I suspect is a major source of overhead).