Section with general information regarding which kind of simulation to perform an
parameters for the whole PROGRAM
Section path:
CP2K_INPUT
/
GLOBAL
This section cannot be repeated.
At the end of the run write a callgraph to file, which contains detailed timing informations.
This callgraph can be viewed e.g. with the open-source program kcachegrind.
Use fft library specific values for the allows number of points in FFTs. The default
is to use the internal FFT lengths. For external fft libraries this may create an
error at the external library level, because the length provided by cp2k is not supported
by the external library. In this case switch on this keyword to obtain, with certain
fft libraries, lengths matching the external fft library lengths, or larger allowed
grids, or grids that more precisely match a given cutoff. IMPORTANT NOTE: in this
case, the actual grids used in CP2K depends on the FFT library. A change of FFT library
must therefore be considered equivalent to a change of basis, which implies a change
of total energy.
FFTW can have improved performance if it is allowed to plan with explicit measurements
which strategy is best for a given FFT. While a plan based on measurements is generally
faster, differences in machine load will lead to different plans for the same input
file, and thus numerics for the FFTs will be slightly different from run to run.PATIENT
planning is recommended for long ab initio MD runs.
The name of the file that contains wisdom (pre-planned FFTs) for use with FFTW3. Using
wisdom can significantly speed up the FFTs (see the FFTW homepage for details). Note
that wisdom is not transferable between different computer (architectures). Wisdom
can be generated using the fftw-wisdom tool that is part of the fftw installation.
cp2k/tools/cp2k-wisdom is a script that contains some additional info, and can help
to generate a useful default for /etc/fftw/wisdom or particular values for a given
simulation.
Specifies the FFT library which should be preferred. If it is not available, use FFTW3
if this is linked in, if FFTW3 is not available use FFTSG. Improved performance with
FFTW3 can be obtained specifying a proper value for FFTW_PLAN_TYPE. Contrary to earlier
CP2K versions, all libraries will result in the same grids, i.e. the subset of grids
which all FFT libraries can transform. See EXTENDED_FFT_LENGTHS if larger FFTs or
grids that more precisely match a given cutoff are needed, or older results need to
be reproduced. FFTW3 is often (close to) optimal, and well tested with CP2K.
FFTW3
a fast portable FFT library. Recommended.See also the FFTW_PLAN_TYPE, and FFTW_WISDOM_FILE_NAME
keywords.
