June 2007 - Comp-phys-alps-users

Transverse Ising-Model
by Armin 13 Jul '07

13 Jul '07

I am trying to calculate the ground state energy of the transverse Ising-Model ( -J*Sx(i)*Sx(j)-h*Sz(i) ) on a simple 1d-chain-lattice with the DMRG and DIRLOOP applications. The results seems to be calculated with a constrained basis even without the CONSERVED_QUANTUMNUMBERS="Sz" parameter (compared to the FULLDIAG where the parameter has its effect on the results). It looks more like the half of a XY-model. So my question is if there is a special problem with the DMRG and DIRLOOP applications and the Ising-Model. Btw, wenn changing the x- and z-axis then the LOOP application gets the same results as the FULLDIAG, but DIRLOOP aborts with an 'Did not find raising and lowering operators' error. best regards, Armin

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2-D heisenberg system
by John Single 06 Jul '07

06 Jul '07

Hello, I am trying to use alps version 2 to simulate a 2-D heisenberg spin ladder model with 2 different (ladder and rail) exchange strengths. In the example for a 1-D chain I changed the lattice to rectangular lattice but I guess that is not the right keyword. Is there an easy way to do this? Thanks, John

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ALPS 1.3b4 released
by Matthias Troyer 30 Jun '07

30 Jun '07

I have put the current ALPS version (1.3b4) on the web. Before the final release there are only a few things that need to be fixed: * correct structure factors for non-square and non-cubic lattices * add evaluation of custom measurements to fulldiag * finalize the documentation Best regards Matthias

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missing graphs in Tutorials:Latticehowto
by Gang Chen 28 Jun '07

28 Jun '07

Hi, all, when I was reading the tutorials, I couldn't see the graphs on the page http://alps.comp-phys.org/mediawiki-1.9.3/index.php/Tutorials:LatticeHOWTO:… Can someone who has the graphs re-post them? Thanks, Gang

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Low performance on APPLE
by Dirk Schuricht 13 Jun '07

13 Jun '07

Dear all, I have a new APPLE with Intel Core 2 Duo Processor which shows very poor performance with all ALPS Applications requiring linear algebra like fulldiag and dmrg. I have already tried to install the ATLAS and LAPACK routines, which had no effect. When installing ALPS and ALPS applications I get the following error message: i686-apple-darwin8-g++-4.0.1: unrecognized option '-pthread' It seems that the pthreads are not working with the standard c- compiler on my system. Is it possible that this causes the poor performance? And if so, what can I do to overcome this problem? Many thanks, Dirk

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Long-ranged Hamiltonians
by Dirk Schuricht 06 Jun '07

06 Jun '07

Dear all, how can I specify an Hamitonian with long-range interactions in the .xml files? For example, I would like to implement the Haldane- Shastry model, i.e. an S=1/2 antiferromagnetic Heisenberg chain whose interaction strength falls off as 1/r^2? Thanks a lot, Dirk

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Low performance on MAC
by Dirk Schuricht 05 Jun '07

05 Jun '07

Dear all, I have installed ALPS 1.35 on my two years old laptop and on my brand- new APPLE. Now the astonishing thing: The dmrg routines from the applications run three to four times faster on my laptop. I have already tried to compile ATLAS, BLAS and LAPACK on the APPLE, but this had no effect on the performance. Is there anything known about performance problems on Macs? Thanks, Dirk

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