restart options

The restart table contains options relating to checkpointing within QMC calculations.

HANDE currently uses one restart file per MPI rank with a filename of the form HANDE.RS.X.pY.H5, where X is the restart index and Y is the MPI rank.

read

type: boolean or integer.

Optional. Default: false.

Start a QMC calculation from a previous calculation if true or an integer. If true, then the highest value of X is used for which a set of restart files exists, otherwise specifies the value of X to use.

Note

The calculation should be the same as the one that produced the ouput file, but it is possible to restart a calculation using an enlarged basis. The orbitals of the old (small) basis must correspond to the first orbitals of the new (larger) basis.

write

type: boolean or integer.

Optional. Default: false.

Write out checkpointing files at the end of the calculation if true or an integer. If true, then the highest value of X is used for which a set of restart files doesn’t exist, otherwise specifies the value of X to use.

write_shift

type: boolean or integer.

Optional. Default: false.

Write out checkpointing files when the shift is allowed to vary (i.e. once target_population is reached) if true or an integer. If true, then the highest value of X is used for which a set of restart files doesn’t exist, otherwise specifies the value of X to use.

write_frequency

type: integer.

Optional. Default: \(2^{31}-1\).

Write out checkpointing files every N report loops, where N is the specified value.

Note

The index used for the restart files created with this option is the next unused index. Depending upon the frequency used, a large number of restart files may be created. As such, this option is typically only relevant for debugging or explicitly examining the evolution of the stochastic representation of the wavefunction.

rng

type: boolean

Optional. Default: true.

Restart the state of the DSFMT random number generator from the previous calculation, allowing restarted calculations to follow the same Markov chain as if the entire series of calculations had been performed as a single calculation.

Note

  1. Calculations using OpenMP threads will not follow the same Markov chain due to the non-deterministic load balancing behaviour of the OpenMP implementation.

  2. Restart files from older restart files do not contain the necessary information to recreate the RNG state. This option is ignored automatically in such cases.

  3. Due to each processor using its own RNG stream, this functionality can only be used when restarting calculations on the same number of processors. Restart files created by the redistribute function will not contain RNG information as a result. This option is automatically ignored in such cases.

  4. The presence of the RNG information in a restart file can be detected by running the command

    $ h5dump -A -d rng/state <restart file>

    where <restart file> is the appropriate filename, which will return some metadata information on the rng/state dataset if the RNG state is present and an error otherwise.