December 2010 - Comp-phys-alps-users

NUMBER_EIGENVALUES and TOTAL_MOMENTUM (ALPS 2)
by Martin Hohenadler 04 Dec '10

04 Dec '10

Dear all, I was trying to specify the number of eigenvalues calculated by sparsediag, using NUMBER_EIGENVALUES=1 as described here: http://alps.comp-phys.org/mediawiki/index.php/Documentation:sparsediag However, sparsediag nevertheless calculates the lowest eigenvalue for each wavevector. Does this option no longer work? The problem persists even for a simple test case: LATTICE="chain lattice" MODEL="spin" local_S=0.5 Jxy=0.0 Jz="-1.0" Gamma=0.5 NUMBER_EIGENVALUES=1 MEASURE_CORRELATIONS[Diagonal spin correlations]=Sz MEASURE_CORRELATIONS[Offdiagonal spin correlations]="Splus:Sminus" {L=20;} A second question pertains to the output of sparsediag. With the above input file, the results contain the line <PARAMETER name="TOTAL_MOMENTUM">5.7595865315812870833</PARAMETER> However, I have not specified TOTAL_MOMENTUM... Any help is appreciated. Best regards, Martin Hohenadler -- ==================================================== Dr Martin Hohenadler ---------------------------------------------------- Institute for Theoretical Physics and Astrophysics University of Würzburg Am Hubland, 97074 Würzburg ---------------------------------------------------- Tel: +49 (0)151 53506248 (mobile) ---------------------------------------------------- email: martin.hohenadler(a)physik.uni-wuerzburg.de web : www.hohenadler.com ====================================================

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Core parallelization and GPU porting
by degliesposti 03 Dec '10

03 Dec '10

Dear ALPS users, I wonder if some of you is experienced and could give us recent insights about these two points: i) core parallelization with ALPS: which parallel environment is better (OpenMP, MPICH, ...) ii) are there any porting/tests of ALPS on GPU's ? Thanks for your time, Cristian Degli Esposti Boschi

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Questions regarding DMRG
by Chong You Quan 03 Dec '10

03 Dec '10

Hi, I'm using ALPS 1.3.5 on Linux currently. I'm new to ALPS and DMRG and I'd just like to clarify a few questions:1. For full DMRG application with verbose = 1 using the Heisenberg (spin) model, what is the basis of the RHO's eigenvalues in the output? DMRG truncates the density matrix, so, the basis of the density matrix is that of the spin sites is it? For example, L = 2, then the basis would be |00>, |01>, |10>, |11>.. is it correct? What about the basis of the matrix after truncation? Also, if I would like to get the full wavefunction in the basis of the sites, what should I do? Also if I specify that N is conserved, what is the default value of N? Or does it try all possible N to give the lowest energy state?2. I can see that ALPS can be integrated into C++ but I tried googling for examples and documentation to no avail.. Is it in the Trac wiki? If so, must one register for it in order to view the documentation? The default documentation seems to specify what the input valu es represent but don't describe much of the output or how to integrate ALPS into C++.. Am I missing out on some way I can find the documentation for ALPS and how to integrate it in C++?3. I noticed there were some .dat files after running the DMRG application.. Are those temporary files stored during calculation or are those actual output files? I didn't seem to be able to extract any form of data from those files.. Is it that all the useful output for the DMRG is written to the screen?4. I'm not sure why but my parameter2xml does not seem to work on any of the example parameter files.. I'm currently just typing out the xml file by hand. Maybe I'm just missing out on something.. Does parameter2xml output to a specific directory or something?5. Almost all of the files on http://www.comp-phys.org/lugano04/Talks.html seem to be broken.. Is it that the links are outdated or something? I'm sorry if some of these questions sound too amateur but this seems to be the best place I can find an answer to these questions.Thanks in advance. Regards,YQ

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