I was using MPS code in ALPS to calculate exited states of the fermion Hubbard model
when there throwed an error
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Sweep 0, optimizing sites 19 and 20
Input <MPS|O[0]> : 0
Output <MPS|O[0]> : -nan
JCD used 8 iterations.
Time elapsed in JCD: 0.19799719
MPS overlap: 0
Energy 1 2.341151156e-310
Exception thrown:
Error in SVD!
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This error vanished when the "total number" was less than 10 or great than 20 (or around) or the 'MAXSTATES' is greater than about 80.
In the attachment I deliver my python script.
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import pyalps
import numpy as np
parms=[]
for L in [40]:
for P in [12]:
# for P in [55,56,57,58,59,60,61,62]:
parms.append({
'LATTICE' : "open chain lattice",
'L' : L,
'MODEL' : "fermion Hubbard",
'CONSERVED_QUANTUMNUMBERS' : 'Nup,Ndown',
'Nup_total' : P,
'Ndown_total' : P,
'mu' : 0.0,
't' : 1.0,
'U' : 0.0,
'SWEEPS' : 4,
'MAXSTATES' : 50,
'NUMBER_EIGENVALUES' : 2,
'storagedir' : 'storage',
})
#write the input file and run the simulation
input_file = pyalps.writeInputFiles('parm_tsc',parms)
res = pyalps.runApplication('mps_optim',input_file,writexml=True)
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