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CASINO HELP SYSTEM
 ==================

 Keyword : vmc_nstep
 Title   : Number of (main) VMC steps
 Type    : Integer
 Level   : Basic

 DESCRIPTION
 -----------
 Total number of VMC steps summed over all processors; this corresponds to
 the total number of particle configurations for which the energy (and other
 quantities to be averaged) are calculated.
 
 Note that because adjacent moves are likely to be serially correlated, there
 is also an inner decorrelation loop of length VMC_DECORR_PERIOD, so the total
 number of configuration moves attempted in a VMC run following equilibration
 is  VMC_NSTEP*VMC_DECORR_PERIOD.
 
 On parallel machines, each core will do the same number of steps and for
 each step the energy is averaged over the cores and written to the vmc.hist
 file (which will ultimately contain VMC_NSTEP/NCORES lines - though
 VMC_AVE_PERIOD adjacent lines may be averaged over to reduce the file size).
 This means that if VMC_NSTEP is not divisible by the number of cores then it
 will internally be rounded up to the nearest multiple of the number of cores
 (example: on a 12-core machine, given VMC_NSTEP=20 in input, CASINO will
 round up VMC_NSTEP to 24; each core will then do two steps and a total of two
 records will be written to vmc.hist, each of which is an average of 12
 energies). On a single-core machine with VMC_NSTEP=20, CASINO will move the
 single config 20 times, and 20 records will be written to vmc.hist.
 
 Note the VMC_NBLOCK keyword may be used to vary the frequency with which
 checkpointing is done i.e. how often we write the data to disk; it does not
 affect the total number of VMC steps and expectation values such as average
 energy should be independent of it.

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CASINO HELP SYSTEM
 ==================

 Keyword : vmc_nblock
 Title   : Number of blocks in VMC
 Type    : Integer
 Level   : Intermediate

 DESCRIPTION
 -----------
 Number of blocks into which the total VMC run is divided
 (post-equilibration). The purpose of VMC_NBLOCK is to determine how often the
 output, history and configuration/checkpoint files are written to. More
 specifically, at the end of each block:
 
 (1) the node- and block-averaged energies and a short 'report' are written
 to out.
 
 (2) the node-averaged energies for each step in the current block are
 appended to vmc.hist (and other quantities to expval.data).
 
 (3) the current VMC state plus any accumulated configs are written to the
 config.out file (this latter only if the CHECKPOINT input keyword is
 increased to 2 from its default value of 1 - otherwise config.out is only
 written after the end of the final block).
 
 Note that the total energy and error bar should be effectively independent
 of VMC_NBLOCK (provided it is ensured that the random number sequence is
 independent of the number of blocks - which it has not been at various
 periods in CASINO's history, though it should be now). Note also that the
 value of VMC_NBLOCK is ignored if VMC_NTWIST>0. The default value of
 VMC_NBLOCK is 1.

Code: Select all

CASINO HELP SYSTEM
 ==================

 Keyword : vmc_nconfig_write
 Title   : Number of configs to write in VMC
 Type    : Integer
 Level   : Basic

 DESCRIPTION
 -----------
 Total number of configurations to be written out in VMC for later use
 (wave-function optimization or DMC). This number must be <= VMC_NSTEP (though
 you may want to set VMC_NSTEP to be significantly greater than
 VMC_NCONFIG_WRITE to get an acceptable error bar on the energy; this is
 useful for e.g. judging the success of an optimization after each stage).
 Since each processor always does the same number of steps, then
 VMC_NCONFIG_WRITE (and VMC_NSTEP) will be rounded up to the nearest multiple
 of the number of processors (e.g. VMC_NCONFIG_WRITE=20 will be rounded up
 internally to 24 on 12 cores, and 24 configs will be written to config.out -
 2 from each core). Note that the config.out file will still be written even
 if VMC_NCONFIG_WRITE is zero, since this file is used to store the current
 state of the system at the end of every VMC block (equivalent to writing one
 config, though of course multiple cores write multiple configs to save the
 state). Writing of config.out may be suppressed completely with an
 appropriate value for the CHECKPOINT keyword, and the data will be held in
 memory between different stages of the calculation.