Comp-phys-alps-users

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1244 discussions

auto-correlation time in hybridization expansion ctqmc calculation
by Jia Chen 21 Sep '14

21 Sep '14

Dear all, I would like to know, if I can have auto-correlation time from hybridization expansion ctqmc simulations. I want to have an estimation of like, if it saturates with interaction parameters and if simulation is long enough. Appreciate your help. Best Wishes Jia

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Problem with ALPS homepage
by Niraj Ghimire 20 Sep '14

20 Sep '14

Dear ALPS users/developers, The "User Workshops" section given on the ALPS homepage ( http://www.comp-phys.org/lugano04/Talks.html) does not work. It just shows the list of talk but none of the items on the list open. I tried it on Mozilla Firefox and Google Chrome (in Ubuntu), didn't work. ~Niraj

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Vispython not working
by Paul Fanto 15 Sep '14

15 Sep '14

Hello, I am trying to install ALPS on a Mac OS X (version 10.7.5). I installed ALPS from binary packages, following the instructions I found on the ALPS website. I also installed the most recent version of VisTrails and the ALPS VisTrails module in order to use Python to implement simulations in ALPS. When I try to call "Vispython" in my terminal, however, I just get an error: "vispython: command not found." Could anyone explain why this is happening and how I can get Python working with ALPS? Thanks very much. Best regards, Paul Fanto Princeton University | Class of 2015 Department of Physics

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mps_optim
by Mateusz Łącki 15 Sep '14

15 Sep '14

Dear All I am trying to compute low energy eigenstates of a small L=10 system of spin-1/2 nodes using the DMRG, implemented as mps_optim to compute a ground state and a first excited state for a cetrain model (model.xml pasted below). Unfortunately what i get is two states, but the state returned as a ground state (numer „0“) as a greater energy then the excited state. More specifically I compute the state twice: using NUMBER_EIGENVALUES=1 (then the gs energy is -4) and NUMBER_EIGENVALUES=2 (then the gs energy is -4 and excited state’s energy is -5 (which is is fact the ground state’s energy). the Fulldiag code returns correct (verified by fulldiag of my own) eigenvalues. The alps-dmrg does not converge in reasonable number of sweeps. What is worse it returns energy of order of -18, so that is significantly below the ground state energy. Does the alps-dmrg support the hamiltonian that I have wrote at all? FINAL SWEEP - LAST ITERATION NUMBER OF STATES: 16 2 2 16 1024 E0 = -17.4530961018 E0 = -8.52509624929 EXCITED OVERLAP(0) = 3.07571832172e-06 E(1) = -8.52509624929 GAP(1) = -17.4530961018 -8.52509624929 8.92799985252 ITER = 4 ENTROPY = 2.62675527051 DMRG as any minimization routine is subject to „local minimum“ problem, but I have never seen it to fail so dramatically. I had the thought that the key may be the following line in the ouput: "This binary contains symmetries: nu1, " but I have set nothing like „N_total=10“. Just to be sure I have redefined „spin“ basis to a new „spinc“ from which I have removed the „constraint" metatag. TO sum up I have following issues/questions: - matter of convergence of mps_optimize - why alps-dmrg returns significantly lower energy than fulldiag on a small exemplary system? - is it some sort of constraints ? I do not want to use any conservation laws. W would like to do a brute DMRG without any good quantum numbers. Kind Regards, Mateusz Łącki Files: *********** input file taken by parameter2xml ********** MODEL_LIBRARY="/home/lacki/alpsdmrg/models.xml" LATTICE="open chain lattice" MODEL="SlonTrabalski" SWEEPS=8 NUMBER_EIGENVALUES=2 NUMSTATES=100 {L=10; V=0.1} ************* /home/lacki/alpsdmrg/models.xml ********** (I post only the modified things) <BASIS name="spinc"> <SITEBASIS ref="spin"> <PARAMETER name="local_spin" value="local_S#"/> <PARAMETER name="local_S#" value="local_S"/> <PARAMETER name="local_S" value="1/2"/> </SITEBASIS> </BASIS> <HAMILTONIAN name="SlonTrabalski"> <PARAMETER name="V" default="0"/> <BASIS ref="spinc"/> <SITETERM site="i"> V*Sx(i) </SITETERM> <BONDTERM source="i" target="j"> -(0.5)*(Splus(i)*Sminus(j)+Splus(j)*Sminus(i))-(0.5)*(Splus(i)*Splus(j)+Sminus(i)*Sminus(j)) </BONDTERM> </HAMILTONIAN>

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dmrg
by Mateusz Łącki 13 Sep '14

13 Sep '14

Dear All, I am still using alps-dmrg for my computation - mps_optim is giving me some troubles, that I will describe later in a separate email. Is is possible to ask the dmrg application to clean its temporary files after computation is done? the folder which I have specified using TEMP_DIRECTORY=/home/lacki/tmp/ is filled with old data. Of course I could write a script that checks launch date of each of „dmrg“ processes currently running and deletes all older files, but it seems really cumbersome. Kind Regards, Mateusz Łącki

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memory usage in DMRG
by Mateusz Łącki 11 Sep '14

11 Sep '14

Dear All, I have been running the following input: <pasted at the bottom> I have observed that for Bose-Hubbard model on chain of length L=256, unit filled, under open boundary conditions the DMRG code uses over 32G memory (this is the hardware limit, it clearly wants more, for L=128 it was around 20G). is that normal? I would estimate that an MPS state of 256 sites, with bond dimension 60, local Hilbert space 7 should be much smaller (even if we allow for a small constant factor for temporary data) Kind Regards, Mateusz Łącki LATTICE="open chain lattice" MODEL="boson Hubbard" SWEEPS=8 Nmax=6 NUMBER_EIGENVALUES=1 L=256 CONSERVED_QUANTUMNUMBERS="N" N_total=256 VERBOSE=0 t=0.25 U=1 mu=0 {MAXSTATES=60}

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additional update
by tesfaye mamuye 10 Sep '14

10 Sep '14

Dear ALPS Developers/users I am using alps CT-QMC(Hybridization expansion) as impurity solver. But the total acceptance rate is getting low and low, and I'm wondering if it may affect the final result. In order to overcome this, I'm thinking to use additional update: 'shift of the segment end point' which is used to enhance the sampling efficiency (to increase the acceptance ratio and reduce auto-correlation times) which do not change the expansion order. However, I didn't get in the documentation on how to implement this additional update as control parameter 'SPINFLIP'={0.1} : specify to whether to perform spin flip update. Is it possible to use for shift of the segment end point update 'N_SHIFT'=1 ? I need help on how to implement this additional update. here is the sample |------ Simulation details (master only) after 2665880 sweeps ------| Total acceptance rate = 22.92% Individual acceptance rate for update change zero state = 0.00% (proposal rate = 10.00%) insert segment = 6.37% (proposal rate = 25.00%) remove segment = 6.37% (proposal rate = 25.00%) insert anti-segment = 5.09% (proposal rate = 20.00%) remove anti-segment = 5.09% (proposal rate = 20.00%) swap segment = 0.00% (proposal rate = 0.00%) |-----------------------------------------------------------------| Thank you for your time

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Help with LiveALPS
by Niraj Ghimire 10 Sep '14

10 Sep '14

Dear ALPS users, I have been running LiveALPS from my USB flash drive and I can't get access to the internet. I could not find any information anywhere on how to resolve this issue. Would you be able to help me out ? ~Niraj

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(no subject)
by hamid mosadegh 07 Sep '14

07 Sep '14

Dear All What is the momentum of , E_1(N_{\uparrow},(N_{\downarrow} ,L), the lowest-excitation energy in the Hubbard model in the S=0 sector. I means, I want to evaluate the velocity of charge excitation from E_1(N_{\uparrow},(N_{\downarrow} ,L)- E_0(N_{\uparrow},(N_{\downarrow} ,L) where E_1(N_{\uparrow},(N_{\downarrow} ,L) is the lowest-excitation energy with momentum k=2\pi/L and total spin S=0. If i run MODEL="fermion Hubbard" CONSERVED_QUANTUMNUMBERS="Nup,Ndown" Ndown_total=10;Nup_total=10 NUMBER_EIGENVALUES=2 what is the momentum of first excitation. is it possible to determine or change it? thanks H. Mosadeq Shahr-e-Kord University (SKU), Shahr-e-Kord , Iran

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the parity sector in DMRG
by hamid mosadegh 03 Sep '14

03 Sep '14

Dear all Is it possible to do the DMRG or ED calculations of fermion Hubbard model in the odd(even) parity sector using ALPS? I need to determine the minimum energies for eigenstates in the even and odd parity sectors. Thanks -- H. Mosadeq Shahr-e-Kord University (SKU), Shahr-e-Kord , Iran

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Comp-phys-alps-users