DevLog:2008-08-26

From QMCPACK

Subversion branches r3039-r3054 have several changes to handle a chain job (opt|vmc|dmc)+.

Added parameters for VMC

• warmupSteps : number of steps without any accumulation
  • There is no need to have multiple vmc blocks, if this is set to be a reasonable number ~100.
• samples : total number of walker configurations stored in memory
  • will be used by optimization or by the next DMC block

Changes in VMC/DMC

• mass of the quantum particle set is used.
  • previously, mass==1 was assumed.

Changes in DMC

• MCWalkerConfiguration::loadEnsenble is called to load the samples to the active walkers
  • The trial energy is recalculated.
• First step during a warmup DMC does not branch.
• During a warmup stage, the trial energy is calculated by a mixture of the running average and the instant energy.
  • Currently

A sample of vmc+dmc on a 64 mpi x 8 threads with a target population of 2560 (40 per mpi node).

  <qmc method="vmc" move="pbyp">
    <estimator name="LocalEnergy"/>
    <parameter name="walkers">  8 </parameter>
    <parameter name="warmupSteps"> 100 </parameter>
    <parameter name="blocks">   16 </parameter>
    <parameter name="steps">    100 </parameter>
    <parameter name="samples">  2560 </parameter>
    <parameter name="timestep">      0.5 </parameter>
  </qmc>
  <qmc method="dmc" move="pbyp">
    <parameter name="blocks">        20 </parameter>
    <parameter name="steps">          1000 </parameter>
    <parameter name="timestep">      0.01 </parameter>
    <parameter name="nonlocalmoves">  yes </parameter>
    <parameter name="warmupSteps">   1000 </parameter>
  </qmc>

There are unresolved problems when the vmc after optimization uses parameter/@name='useDrift' is turned on.