Re: [ccp4bb] Refmac executables - win vs linux in RHEL VM

- Protein crystallography

Main steps:

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Special:

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

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Subject: Re: Refmac executables - win vs linux in RHEL VM
From: Roger Rowlett rrowlett {- at -} COLGATE {- dot -} EDU
Date: 2012-04-07

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From: Eric Bennett ericb {- at -} POBOX {- dot -} COM
Date: 2012-04-07

Subject: Re: Refmac executables - win vs linux in RHEL VM
From: Nat Echols nathaniel {- dot -} echols {- at -} GMAIL {- dot -} COM
Date: 2012-04-07

On Sat, Apr 7, 2012 at 9:50 AM, Roger Rowlett wrote:
> I don't know the state of current software, because I haven't tried
> recently, but when I set up my student crystallography workstations a few
> years back I noticed many packages (e.g. EPMR, Phaser) that had potentially
> long run times (where it is really noticeable) would run on the identical
> hardware about 2-3 times faster in Linux than in Windows XP. Memory swapping
> wasn't the issue. I was astounded there could be that much overhead in
> Windows. A Linux VM on a windows machine being faster than native Win7 is
> pretty weird, though.

Different compiler implementations will often have a huge effect on
runtimes. I recently spent some time trying to get a large amount of
C++ code (converted from F77) to compile under Visual C++ 9.0, and I
had to disable optimization of at least ten different functions to
prevent cl.exe from crashing. This was not especially complex code
(and g++ never complains) - just nested 'for' loops over three
dimensions. I did not attempt to compare runtimes since I was running
Windows in a virtual machine on a Mac, but I would be surprised if the
resulting Windows binaries were not slower on identical hardware. And
even if the compiler isn't broken, the math libraries may be; one of
my colleagues found (on Linux) that the exp() function provided by g77
was 20-fold slower than the equivalent in the Intel math library.

So I suspect it is related to the compilers (and optimization flags)
used by CCP4 for these platforms. Another good reason to avoid
Windows!

-Nat

CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: Refmac executables - win vs linux in RHEL VM
From: Roger Rowlett rrowlett {- at -} COLGATE {- dot -} EDU
Date: 2012-04-07

Next message:
Subject: Re: very informative - Trends in Data Fabrication
From: Eric Bennett ericb {- at -} POBOX {- dot -} COM
Date: 2012-04-07