ALPS 2 Tutorials:MC-01 Equilibration

Equilibration

Rule of thumb: All Monte Carlo simulations have to be equilibrated before taking measurements.

Example: Quantum Monte Carlo (directed worm algorithm) simulations

As an example, we consider a Quantum Monte Carlo simulation implemented in the directed worm algorithm for boson Hubbard model in square lattice geometry of size 20².

Using command line

The parameter file parm1a:

LATTICE="square lattice"
MODEL="boson Hubbard"

L=20  
Nmax=20

t=1.
U=16.
mu=32.

THERMALIZATION=10000
SWEEPS=100000 
SKIP=400

{T=1.0}

We first convert the input parameters to XML and then run the application dwa:

parameter2xml parm1a
dwa parm1a.in.xml

Using Python

Script file tutorial1a.py:

import pyalps

parms = [];
for T in [0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0]:
  parms.append({
    'LATTICE'         : "square lattice",          
    'MODEL'           : "boson Hubbard",
    'L'               : 20,
    'Nmax'            : 20,
    't'               : 1.,
    'U'               : 16.,
    'mu'              : 32.,
    'T'               : T,
    'THERMALIZATION'  : 10000,
    'SWEEPS'          : 100000,
    'SKIP'            : 400
  })

input_file = pyalps.writeInputFiles('parm1a',parms)
res = pyalps.runApplication('dwa',input_file)