# 1/inf =? ifort says NaN

**URL:** <https://fortran-lang.discourse.group/t/1-inf-ifort-says-nan/4883>\
**Category:** Help\
**Created:** [December 8, 2022, 8:31am UTC](https://fortran-lang.discourse.group/t/1-inf-ifort-says-nan/4883 "2022-12-08T08:31:25Z")\
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**Author:** ![sblionel](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/sblionel/32/853_2.png) [@sblionel](https://fortran-lang.discourse.group/u/sblionel)\
**Post date:** [December 8, 2022, 5:05pm UTC](https://fortran-lang.discourse.group/t/1-inf-ifort-says-nan/4883/4 "2022-12-08T17:05:08Z")

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Optimizing compilers orften have default behaviors that favor performance over edge-cases, such as full IEEE semantics. The Fortran standard is completely silent on this topic. In the case of ifort, you need the `strict` option if you will be using anything from IEEE\_EXCEPTIONS and possibly even IEEE\_ARITHMETIC.

How realistic is it to expect a real-world application to be doing 1/Inf?

For another example, see [Strange behavior of `ifort` - Fortran Discourse (fortran-lang.discourse.group)](https://fortran-lang.discourse.group/t/strange-behavior-of-ifort/4846/13)

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