https://github.com/equipez/infnan
Fortran functions for checking Inf/NaN. They should work even if the compilers are invoked with aggressive optimization flags such as `gfortran -Ofast`.
https://github.com/equipez/infnan
floating-point fortran inf nan numerical
Last synced: 4 months ago
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Fortran functions for checking Inf/NaN. They should work even if the compilers are invoked with aggressive optimization flags such as `gfortran -Ofast`.
- Host: GitHub
- URL: https://github.com/equipez/infnan
- Owner: equipez
- License: lgpl-3.0
- Created: 2021-09-16T03:34:28.000Z (over 4 years ago)
- Default Branch: main
- Last Pushed: 2024-06-14T07:56:06.000Z (almost 2 years ago)
- Last Synced: 2025-10-09T21:55:28.257Z (8 months ago)
- Topics: floating-point, fortran, inf, nan, numerical
- Language: Fortran
- Homepage:
- Size: 466 KB
- Stars: 9
- Watchers: 1
- Forks: 1
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- Codeowners: .github/CODEOWNERS
Awesome Lists containing this project
README
# infnan
`infnan.f90` implements a module that provides some functions for checking Inf/NaN. They aim to work
even when compilers are invoked with aggressive optimization flags, including particularly `gfortran -Ofast`.
Many ways exist to implement functions like `is_nan`. However, not all of them work with
aggressive optimization flags. For example, there are such discussions on
[StackOverflow](https://stackoverflow.com/questions/15944614) and [Fotran Discourse](https://fortran-lang.discourse.group/t/checking-inf-nan-when-compilers-are-invoked-with-aggressive-optimization-flags/1851).
The `ieee_is_nan` included in `ieee_arithmetic` of `gfortran 9.3.0` does not work with aggressive
optimization flags like `-Ofast`.
Given the fact that `-Ofast` implies `-ffinite-math-only`, we cannot blame `ieee_arithmetic` for
the failure. In addition, some compilers
(`gfortran 9.3.0`, `ifort 21.0`, and `nagfor 7.0`) may not behave in the most desirable way concerning
the return kind of `ieee_is_nan` when some special compilation flags are imposed, as has been discussed
on [Fortran Discourse](https://fortran-lang.discourse.group/t/is-this-expected-fortran-standard-is-not-respected-by-gfortran-fdefault-integer-8-ifort-i8-or-nagfor-i8).
My choice of implementation is totally empirical, in the sense that I have not studied in-depth what
the aggressive optimization flags really do, but only made some tests and found some implementation
that worked correctly. In other words, I do not know why my implementation works but other
implementations may not. The story may change when compilers are changed/updated.
The good news is, I have tested the functions using ten compilers with the most
aggressive optimization flags that I can figure out, and they all succeeded. In particular, the functions work well with `gfortran -Ofast` for `gfortran` 9.3.0 and 10.3.0,
but those based on `ieee_arithmetic` fail. Such a test can be done by
```
cd test && make clean && make gtest
```
However, we did observe failures.
See the [issues](https://github.com/zaikun/infnan/issues) for details. I will be very happy to hear your suggestions on how to fix them.