[gmx-developers] trajana.h trajana.c

Tsjerk Wassenaar tsjerkw at gmail.com
Wed Apr 11 11:26:09 CEST 2012

Hi Paolo,

If you use masking and other bitwise operations, it is handy to know
which bit is set; the second for ANA_USE_TOPX and the fifth for
ANA_NOUSER_PBC. Of course it's equal to 2 and 16, but that notation
makes it a bit less obvious what to do with bitwise operations.



On Wed, Apr 11, 2012 at 11:18 AM, Paolo Franz <paolo.franz at gmail.com> wrote:
> Hello everybody,
> For sometimes, I have been developing analysis tools for gromacs
> trajectories using the gromacs library. I am puzzled about some definitions
> in the file trajana.h, which I do not seem to understand completely. Why are
> definitions such as
> #define ANA_USE_TOPX         (1<<1)
> #define ANA_NOUSER_PBC       (1<<4)
> used in the code? What is the purpose of this bitwise shift - why not set
> ANA_USE_TOPX and ANA_NOUSER_PBC to 2 and 16 for instance??
> Thanks in advance
> Paolo
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Tsjerk A. Wassenaar, Ph.D.

post-doctoral researcher
Molecular Dynamics Group
* Groningen Institute for Biomolecular Research and Biotechnology
* Zernike Institute for Advanced Materials
University of Groningen
The Netherlands

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