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It looks a bit sloppy to hardcode so many constants in a single file: `src/gauss_quadrature/legendre.rs`. Isn't it possible to generate them with the help of ru
by JanisErdmanis 2y ago
It looks a bit sloppy to hardcode so many constants in a single file: `src/gauss_quadrature/legendre.rs`. Isn't it possible to generate them with the help of rust macros in the same way Julia uses metaprogramming?
- ok123456 2y agoGaussian quadrature points are typically solved numerically. There's a good chance these ultimately came from a table. Additionally, compile time floating-point evaluation is limited. When I looked around recently, I didn't see a rust equivalent of gcem; any kind of transcendental function evaluation (which finding Gaussian quadrature points absolutely would require) would not allow compile-time evaluation.
- AlotOfReading 2y agoSupport for float const fns was merged just a couple months ago and hasn't been officially announced yet.
- ok123456 2y agoIIRC, that only supports elementary arithmetic operations. Useful but not general.
- AlotOfReading 2y agoIt's relatively straightforward to build transcendental functions out of the basic operations and the stdlib support will eventually get there, but rust's float story is still a work in progress. They're trying to do things more properly and document semantics better than C and C++ have.
- BD103 2y agoSupport for constant float operations was released in Rust 1.82! https://blog.rust-lang.org/2024/10/17/Rust-1.82.0.html https://blog.rust-lang.org/2024/10/17/Rust-1.82.0.html
- zokier 2y agoI was under the impression that macros can execute arbitrary code, surely some FP would not be big problem. And if not macros then build.rs script certainly could do the trick.
- dhosek 2y agobuild.rs can definitely execute arbitrary code, which means that a lot of places (including, IIRC crates.io) will forbid crates that rely on build.rs. I ended up refactoring my build.rs into a separate sub-application in finl_unicode that built data tables which are then checked into git and used pre-built. I include the sub-app in the source code so that anyone with access to the repo could continue development if I were to die tomorrow.
- n_plus_1_acc 2y agoThere are many crates with build.rs scripts on crates.io, because they host just the source code with the Cargo.{toml,lock}.
- dhosek 2y agoI ran into some issues with crates.io and my build.rs when I first released the crate, although it’s long enough ago, that I don’t remember exactly what the issue was. It might also have been that the build.rs script downloaded raw data files from unicode.org
- Arnavion 2y agocrates.io doesn't care what your build.rs does because it doesn't try to compile your code, neither now or ever in the past. There would be no point in it trying to compile your code; there are lots of crates that are bindings to C libraries that crates.io's builders can't be expected to have, crates that target architectures which crates.io can't be expected to have builders for, etc.
- two_handfuls 2y agoProbably but that would slow down compilation a lot.
- simlevesque 2y agoExactly, it's not like the constants are gonna change.
- blharr 2y agoYou wouldn't have to recompile them every time. What if you didn't necessarily use macros but auto-generated it in a file that you keep separate from the other code at the bottom?
- dataflow 2y agoWhat I would do in these cases is to define the general computation function, but special-case it to return the hard-coded value for specific common inputs if it's being evaluated at compile time. Then add a test to verify both behaviors.
- mtantaoui 2y agothis was mainly to use an Iteration free method in this paper: https://www.cfm.brown.edu/faculty/gk/APMA2560/Handouts/GL_quad_Bogaert_2014.pdf https://www.cfm.brown.edu/faculty/gk/APMA2560/Handouts/GL_qu... this method is much faster and simpler.