[RegCNET] compiler option -fp-model precise

[Raymond Arritt]

Dear friends,

In doing some tests with RegCM4 using various options for the Intel compiler I have 
found that the option "-fp-model precise" slows down the model by around 15%.  This 
option is specified by default in RegCM4.  A writeup from Intel explains some of the 
reasoning behind use of this option:
http://software.intel.com/file/32018/

I am curious as to whether anyone has tested RegCM4 with and without this option to 
see what *practical* effect it has on the model results; i.e., whether the concerns 
noted in the Intel document are significant in practice.  The Intel document notes 
that results from a WRF run were "slightly different" without this option, but 
doesn't specify what "slightly different" means.

If it can be turned off with little or no effect on model results then this would 
increase execution speed by a noticeable amount.  Although the difference of 15% in 
execution speed is not huge, for long runs it could mean a week or so in terms of 
time to complete a simulation.

Thanks
Ray


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  Raymond W. Arritt                       tel       +1-424-242-0329
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