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Written by Dominik Domin
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Monday, 21 March 2005 |
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The generation of walkers in Zori tends to be very simple and rapid once you have good psi and orbitals files from the previous trial wave function creation step. A sample input file (create.xml) for the creation of walkers is included in the examples TAR archive file that can be obtained from the DOWNLOADS section. Modify the create.xml file so that the number of “Particles” is equal to the number of electrons and that the “TargetEnergy” is reasonably close to energy of you trial wave function. In this section examples of how to create single and multiprocessor walker files (both XML and HD5 formats) in the LAM MPI environment is described.
Description of important tags in create.xml input file.
WalkersPerProcessor = self-explanatory: how many walkers per processor will be produced.
TargetEnergy = walkers produced will be distributed around this Energy. It should correspond approximately to the energy of the trial wave function.
Tolerance = this parameter controls the tolerance on the acceptance of generated configurations when their energies deviate from the TargetEnergy. Setting this parameter too small increases the time needed to generate the walker file. Setting it too large produces high-energy configurations that may get stuck in the QMC calculation or produce "cannot compose determinant" errors.
Dimensions = Currently only 3-D is implemented in Zori
Particles = this usually corresponds to the number of electrons in the atom or molecule
XML format walkers
The command to create the walkers in XML format on a single processor and store them in a file called walkers-0.xml is for example:
zori -n -i create.xml -p hno-psi.xml -w walkers
The "-n" option is necessary so that Zori will not attempt to read walkers from a nonexistent walkers file.
The "-w" option causes the walkers to be stored in a file with the prefix ("walkers") specified followed by the processor number ("-0.xml").
To modify this command for Zori to generate, for example, 6 walker files for a 6 processor calculation just preface the zori command by the mpirun command that is specific for your version of mpi. For LAM-MPI the command would be:
mpirun -np 6 zori -n -i create.xml -p hno-psi.xml -w walkers
This would generate the files walker-0.xml, walker-1.xml, walker-2.xml, walker-3.xml, walker-4.xml, walker-5.xml.
HD5 format walkers
Once you have the walker file(s) in XML format convert them into the HD5 format by the following command:
zori -K -X -i create.xml -p hno-psi.xml -r walkers -w theSingleHD5walkerFile
Note this will generate a single HD5 walker file ("theSingleHD5walkerFile.hd5") from all of the XML walker files if you preceed the zori command with a mpirun command
The "-K" option skips any walk specified by the "-i" option and only proceeds in the walker conversion.
The "-X" option converts XML walkers specified by "-r" and outputs the HD5 walkers into the HD5 file specified by "-w"
Conversion from HD5 to XML is possible by using the "-V" switch instead of "-X"
mpirun -np 6 zori -K -V -i create.xml -p hno-psi.xml -w zwalkers -r walkerFile.hd5
6 XML walker files ("zwalkers-*.xml") are generated as expected.
Now that you have walkers you are ready to proceed with a VMC calculation. |
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Last Updated ( Monday, 21 March 2005 )
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