# How to show the true wall time instead of cpu\_time?

**URL:** <https://fortran-lang.discourse.group/t/how-to-show-the-true-wall-time-instead-of-cpu-time/2189>\
**Category:** Uncategorized\
**Created:** [October 29, 2021, 6:44am UTC](https://fortran-lang.discourse.group/t/how-to-show-the-true-wall-time-instead-of-cpu-time/2189 "2021-10-29T06:44:25Z")\
**Posts on this page:** 1\
**Showing post:** 9

<div class="post-metadata">

**Author:** ![tomohirodegawa](https://avatars.discourse-cdn.com/v4/letter/t/51bf81/32.png) [@tomohirodegawa](https://fortran-lang.discourse.group/u/tomohirodegawa)\
**Post date:** [October 29, 2021, 3:40pm UTC](https://fortran-lang.discourse.group/t/how-to-show-the-true-wall-time-instead-of-cpu-time/2189/9 "2021-10-29T15:40:21Z")

</div>

> What is the practical limit with `integer(int64)` ?

For the compilers I used, practical upper limits with `integer(64)` are shown below:

| compiler | upper limit | count rate |
| --- | --- | --- |
| Intel | 290000 years | 1000000 |
| PGI | 29000 years | 10000000 |
| GNU | 290 years | 1000000000 |

I agree with what gfortran docs says.  
I NOW think that `system_clock` should be used with `integer (int64)`.  
My previous post is a pitfall I fell into when I didn’t know that.

---

_[View the full topic](https://fortran-lang.discourse.group/t/how-to-show-the-true-wall-time-instead-of-cpu-time/2189)._