The CASINO forum

The errors in the DMC Green's function, in f(R) and hence in the energy can be of either sign. In my experience time-step bias in the energy is usually, but not always, positive.

Best wishes,

Neil.

Dear Manuel,

Unfortunately this isn't readily available or implemented, and thought would be required...

Best wishes,

Neil.

Dear Vladimir, One argument for the time-step bias in the energy being linear is that the time-step error in the DMC Green's function is O(tau^2), and hence time-step errors are introduced at a rate O(tau^2)/tau=O(tau) into the mixed wave function f ( R , t )=phi( R , t ).Psi( R ), where Psi( R ) is...

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Dear Vladimir, I played around with "accelerated" Metropolis VMC methods in about 2002 and concluded that one can easily come up with transition probability densities that require fewer Monte Carlo iterations to achieve a given error bar; however, none of these methods was actually more ef...

Dear Vladimir, Thanks very much for reporting the problem and sorry for any inconvenience. The bug was introduced in 2.13.650. The issue is that mdet_max_mods needs to be broadcast before it is used in READGW in gaussians.f90. I've attached the git patch that I've just sent to Mike. Happy New Year! ...

Dear Vladimir,

Thanks for the report. Do you have an example that fails? (The MDET examples in CASINO/examples/TEST seem to work OK, at least with the gfortran and NAG compilers.)

Best wishes,

Neil.

Dear Vladimir, Sadly it doesn't make CASINO scale linearly with problem size. The cost of evaluating the wave function (or calculating a local energy, etc.) is usually dominated by the cost of evaluating the Slater wave function. For a localised basis set (e.g., blips or Gaussians but not plane wave...

Dear Katharina, Yes, sorry, I meant that it is usually best to aim for consistency in the cutoff lengths between different calculations when calculating energy differences or calculating results to be combined in some way. For example, when studying condensed matter I usually set the cutoff length f...

To be honest I don't usually bother optimising cutoff lengths these days. It's usually more important to be consistent with one's choice of cutoff lengths. When an optimisation goes wrong try the following: reducing the number of parameters (can increase it again later); increasing the number of con...