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Re: 20040920: performance enhancement for NetCDF F90 Interface

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  • Subject: Re: 20040920: performance enhancement for NetCDF F90 Interface
  • Date: Tue, 21 Sep 2004 16:25:09 -0600
>To: address@hidden
>From: Mathis Rosenhauer <address@hidden>
>Subject: NetCDF F90 Interface
>Organization: German Climate Computing Center
>Keywords: 200409211415.i8LEFLnJ002151 netCDF Fortran90

Hi Mathis,

Wow, I'm surprised no one else noticed that problem, I think it will
make a big difference to anyone using the Fortran 90 interface.  It
looks like the original code never called any of the
nc_{put,get}_vara_ functions, but instead just used the
nc_{put,get}_varm_ functions with a default map to emulate them,
greatly increasing the function call overhead.

On behalf of the users of the netCDF f90 interface, thank you!  I will
put this fix into the 3.6.0 release immediately.

--Russ


On 21 Sep 2004 09:11:23 -0600, Mathis Rosenhauer wrote:

Hi Russ,

I am working with some code here which uses the fortran 90 interface
of NetCDF. The performance of writing NetCDF files was very poor
compared to raw output. The code calls nf90_put_var() with simple
arrays, no stride or map. However, it ends up in nc_put_varm_double()
which calls nc_put_vara_double() very often. On our NEC SX6 this
caused a huge overhead.

Attached is a patch which may help other platforms as well - unless I
broke something. I stripped out all SX specific stuff. The patch is
against 3_6_0-beta3 but should also work with older versions.

Cheers,

Mathis

-- 
Mathis Rosenhauer                  http://www.dkrz.de/whois?rosenhauer
Application Software               Phone: +49 40 41173 395
German Climate Computing Center    Pavillon 107

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