[ALPS-users] Maybe a DataSet.props bug for ALPS MPS Project

13 Dec 2017

      Dear all,

I found an interesting wrong var assignment in ALPS MPS Project version: MAQUIS repo r4143 (2013-2014). It appears both on OSX bmg package version and builds from source code version on Linux. You can use the following simple script to reappear the problem:

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#

#  Author: Rongyang Sun <sun-rongyang@outlook.com>

#  Date: 2017-12-13 11:59

#  Last Modified Date: 2017-12-13 11:59

#  Last Modified By: Rongyang Sun <sun-rongyang@outlook.com>

#

#  Description: A demo to show the interesting bug

#

import pyalps

#prepare the input parameters

parms = [ {

        'LATTICE'                   : "open chain lattice",

        'MODEL'                     : "spin",

        'CONSERVED_QUANTUMNUMBERS'  : 'N,Sz',

        'Sz_total'                  : 0,

        'J'                         : 1,

        'spin'                      : 1,

        'SWEEPS'                    : 4,

        'NUMBER_EIGENVALUES'        : 1,

        'L'                         : 10,

        'MAXSTATES'                 : 100

       } ]

input_file = pyalps.writeInputFiles('bug',parms)

res = pyalps.runApplication('mps_optim',input_file,writexml=True)

data = pyalps.loadEigenstateMeasurements(pyalps.getResultFiles(prefix='bug'),verbose=True)

print("\nMODEL: {0}".format(str(data[0][0].props['MODEL'])))

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It will return "MODEL: 1" not the right "MODEL" parameter because I define an unused parameter 'spin' with value 1. Once a parameter with a name which appears at the value of 'MODEL', it will be replaced by the value of the parameter. It is more severe for 't-J' model case. if you set 't': 1.0 and 'J': 0.5, 'MODEL' will be assigned as 0.5 which equals 1.0('t') - 0.5('J')! I have checked the output hdf5 file and found that the wrong replace had happened in the file. That means it may be a bug about ALPS MPS code.

Best regards,

Rongyang Sun