QMCPACK FAQ
From QMCPACK
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Contents |
[edit] General
[edit] Can I edit wiki?
Only registered users are allowed to edit wiki including posting questions here. Anyone can create an account at Create account. But, note that some pages are limited to QmcDev group.
[edit] Installation
[edit] I want to disable MPI on my workstation. How to do it?
Currently, the default is to enable MPI. Do one of these
Before cmake
- Set QMC_MPI=0 in your shell by
export QMC_MPI=0 - Edit top-dir/CMakeLists.txt
SET(QMC_MPI 0 CACHE BOOL "Enable/disable MPI")
After cmake is completed, check:
- build-dir/CMakeCache.txt
QMC_MPI:BOOL=0 - Change QMC_MPI cache value.
[edit] Can I disable OpenMP?
Yes, by changing QMC_OMP similarly to QMC_MPI.
However, there is no reason to disable OpenMP if your compilers can support it. These compilers are tested for OpenMP:
- GNU 4.2.x and higher
- Intel compilers
- IBM XLC
[edit] External tools and libraries
[edit] Running
[edit] What criterion does the optimization use for stopping?
Typical parameters used for optimizations are
<optimizer method="cg">
<parameter name="max_steps">10</parameter>
<parameter name="tolerance"> 1e-6 </parameter>
<parameter name="stepsize"> 0.05 </parameter>
<parameter name="epsilon"> 1e-4 </parameter>
</optimizer>
The max_steps is the number of CG minimization steps which should be roughly proportional to the number of variables to be optimized.
The tolerance is the stopping criteria, i.e., the minimization will be terminated if 
is less than the tolerance. But, this is seldom satisfied.
Using a loop is recommended over running a long minimization using a large max_steps.
[edit] How to repeat the optimizations?
Use loop section as
<loop max="5">
<qmc method="optimize">
... everything else for optimization ...
</qmc>
</loop>
loop/@max sets the number of iterations. Each iteration generates un-correlated configurations by VMC which are then used for optimizations by correlated samplings.
loop section can have other qmc (vmc/dmc/rmc) sections too.
[edit] Where is the optimized wavefunction?
Files with *.opt.#.xml and *.opt.xml are created during the optimization.
- *.opt.#.xml where # is the CG step.
- *.opt.xml is the final wavefunction for a qmc/@method="optimize" section.
Include any of these files instead of the original wavefunction section. Be careful not to duplicate the wavefunction components.
[edit] Is there any pseudopotential database?
Not yet but we are working on it. What format we are using is an entirely different question but more important than anything else. Since there is "no standard" yet, we are using various formats. Check out pseudopotentials. We plan to have a drop-off place to which customized pseudopotentials after extensive testing by the contributors can be submitted.
