# Gfortran compiling options

**URL:** <https://fortran-lang.discourse.group/t/gfortran-compiling-options/1847>\
**Category:** Help\
**Created:** [September 15, 2021, 3:30pm UTC](https://fortran-lang.discourse.group/t/gfortran-compiling-options/1847 "2021-09-15T15:30:57Z")\
**Posts on this page:** 1\
**Showing post:** 12

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**Author:** ![CRquantum](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/crquantum/32/730_2.png) [@CRquantum](https://fortran-lang.discourse.group/u/CRquantum)\
**Post date:** [September 16, 2021, 12:22am UTC](https://fortran-lang.discourse.group/t/gfortran-compiling-options/1847/12 "2021-09-16T00:22:08Z")

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Thank you very much!

Do you have suggestions about what flags to use for ‘release mode’?

By the way, in my another topic,

> [@Why solving two differential equations is 8 times slower than solving one?](https://fortran-lang.discourse.group/t/why-solving-two-differential-equations-is-8-times-slower-than-solving-one/1842/5):
>
> compiler flag: /nologo /debug:full /O3 /QxHost /assume:buffered\_io /heap-arrays0 /Qipo /debug-parameters:all /module:“x64\Release\” /object:“x64\Release\” /Fd"x64\Release\vc150.pdb" /traceback /libs:static /threads /Qmkl:cluster /c linker flag: /OUT:“x64\Release\stochastic\_RK.exe” /INCREMENTAL:NO /NOLOGO /MANIFEST /MANIFESTFILE:“x64\Release\stochastic\_RK.exe.intermediate.manifest” /MANIFESTUAC:“level=‘asInvoker’ uiAccess=‘false’” /DEBUG /PDB:“D:\Works CHLA\stochastic\_RK\stochastic\_RK\stochast…

It seems really the 8 times slow down is caused by my random number generator. Thank you very much for bring that to my attention!

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