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Reducing Memory Used by Sparse Diagonalization
by Israel Reichental 12 May '13

12 May '13

Hello, I would like to diagonalize a quantum system of 16 sites, with two quantum numbers, Sz and Tz, each can take two values: 1/2 and -1/2. I would also like to impose the constraint Sz_total=0 and Tz_total=0. In this case, the Hilbert space size would be (16 choose 8)^2 / 16, where the division by 16 is due to translational symmetry. I assume that the amount of memory required to store the Lanczos vector would be (16 choose 8)^2 / 16 * 128 ~ 1.3GB. However, when I run the sparsediag for this system, it requires ~21GB, which exceeds my 8GB RAM. I guess it happens because the application tries to diagonalize all momentum blocks in parallel (1.3*16 ~ 21). Is there a way to diagonalize each block seperately, so the application would not be using the virtual memory? Another question related to memory usage reduction: The system's ground state does also have the property of SzTz_total = 0. This reduces the Hilbert space's size further (by a factor of ~2.6), however I could not find a way to implement this constraint, since it does not depend on a self standing quantum number but determined by the two others. Is there another way to take advantage of this constraint, nevertheless? Thank you very much, Israel System details: Ubuntu 12.10 64bit Intel® Core™ i7-2600 CPU @ 3.40GHz × 8 Compiled with gcc and MKL 11.0 Update 3

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3D susceptibility of weakly interacting chains
by Zlata Pchelkina 09 May '13

09 May '13

Dear users, I cannot understand the magnitude of ALPS susceptibility. If I have the chain, I get results in agreement with Bonner-Fisher (PR 135, A640 (1964)), if I take into account that the Heisenberg model in their paper is defined as 2J*S_i*S_j while in ALPS it is written as J*S_i*S_j and summation in both cases runs only once. But than I plot the susceptibility for 3D structure (for that purpose I write my own graph) with the strong exchange along one direction (706 K) and two very small exchanges in two other directions (3.2 K and 4.6 K), I get the susceptibility about two times larger. I also run calculation with only one exchange along the chain (706 K) and two others equal 0, but the susceptibility is the same as in previous case (with three exchange interactions). Can you please help me to find that I am doing incorrectly? As far as I understand if I have pure chain and if I have chains in 3D structure with exchange between the chains equal 0 I should obtain the same results (namely, Bonner-Fisher). With best regards, Zlata. PS I attached the files with different susceptibilities and my graph.

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the conservation of particle number in DMRG
by Bo-Nan JIANG 07 May '13

07 May '13

Hi, Matthias Your last mail said: "This depends on the formulation of DMRG that you are implementing. I would suggest that you look at some recent reviews." And would you be so kind to give me a list of several these "recent reviews". Thanks a lot!!! Bo-Nan -- Stay foolish,Stay hungry.

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Re: [ALPS-users] how to realize conservation of particle number when DMRG
by Bo-Nan JIANG 06 May '13

06 May '13

Hi,Matthias I mean if I want to program myself, but not using ALPS, is there a general way to realize the conservation of particle number? (For I find this function in ALPS is really easy to use, so I am wondering how you guys program it. But, what I really need is a workable and general way to solve this problem when coding.) Bo-Nan -- Stay foolish,Stay hungry.

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Re: [ALPS-users] Comp-phys-alps-users Digest, Vol 86, Issue 2
by Bo-Nan JIANG 05 May '13

05 May '13

Hi,Matthias I mean if I want to program myself, but not using ALPS, is there a general way to realize the conservation of particle number? (For I find this function in ALPS is really easy to use, so I am wondering how you guys program it. But, what I really need is a workable and general way to solve this problem when coding.) Bo-Nan 2013/5/4 <comp-phys-alps-users-request(a)lists.phys.ethz.ch> > Send Comp-phys-alps-users mailing list submissions to > comp-phys-alps-users(a)lists.phys.ethz.ch > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.phys.ethz.ch/listinfo/comp-phys-alps-users > or, via email, send a message with subject or body 'help' to > comp-phys-alps-users-request(a)lists.phys.ethz.ch > > You can reach the person managing the list at > comp-phys-alps-users-owner(a)lists.phys.ethz.ch > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Comp-phys-alps-users digest..." > > > Today's Topics: > > 1. Re: conservation of particle number in ALPS (Matthias Troyer) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 3 May 2013 08:30:16 -0400 > From: Matthias Troyer <troyer(a)phys.ethz.ch> > To: comp-phys-alps-users(a)lists.phys.ethz.ch > Subject: Re: [ALPS-users] conservation of particle number in ALPS > Message-ID: <CE903F1B-5580-48A9-A2D1-BC08083F3491(a)phys.ethz.ch> > Content-Type: text/plain; charset=iso-8859-1 > > Hi Bo-Nan, > > what do you mean by " how to do it in your source code "? > > Matthias > > On May 2, 2013, at 1:54 AM, Bo-Nan JIANG <bonanjiang(a)gmail.com> wrote: > > > Hi,all > > > > Though it is really easy to realize the conservation of particle number > in ALPS when doing DMRG, I am wondering how to do it in your source code > (for example C++ or fortran) or the scheme of it. Any tips? Thanks a lot! > > > > Bo-Nan > > > > -- > > Stay foolish,Stay hungry. > > > > End of Comp-phys-alps-users Digest, Vol 86, Issue 2 > *************************************************** > -- Stay foolish,Stay hungry.

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conservation of particle number in ALPS
by Bo-Nan JIANG 03 May '13

03 May '13

Hi,all Though it is really easy to realize the conservation of particle number in ALPS when doing DMRG, I am wondering how to do it in your source code (for example C++ or fortran) or the scheme of it. Any tips? Thanks a lot! Bo-Nan -- Stay foolish,Stay hungry.

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Units of susceptibility from ALPS
by Zlata Pchelkina 23 Apr '13

23 Apr '13

Dear users, can you please help me to understand in that units I get the susceptibility in ALPS and how to transform it in common emu/mol or cm-3/mol? If I plot the susceptibility for the chain, it is quite easy - on the Y axis I've got |J|*chi/g^2*mu_B^2*N, N - number of spins in the chain. But if I have 3D lattice, what is the N in this case? As far as I understand, it is not just number of unit cells. Thank you for your cooperation.

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Running ALPS worm/dir_loop in a cluster
by Francisco Cordobés 02 Apr '13

02 Apr '13

Hi to all, I am planning on running some large 2D Bosons simulations with ALPS in a cluster. Specifically I will we using the worm algorithm(and dir_loop for some checks). The cluster I am running my simulations in uses a PBS queuing system. All the tutorials and examples I have seen online are for single machine or assuming one doesn't have to use a queuing system. Is there any PBS functionality implemented in pyalps? Also, and this is a practical question, for running large simulations with ALPS, I understand from the examples and documentation that the best way to do it is to set a very large number of sweep steps and then run it for a fixed time. After that time check if the measurements I am interested in have converged and if not, run it for a bit longer. Is that the best option or is there a better way of doing it? Thanks in advance, Francisco Cordobes

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What am I doing wrong?
by Jakub Zakrzewski 01 Apr '13

01 Apr '13

Hello everybody, Let us take such a simple input file with irrelevant name parbh: LATTICE="open chain lattice" MODEL="boson Hubbard" L=8 Nmax=4 N_total=8 NONLOCAL=0 U = 1.0 t = 0.24 CONSERVED_QUANTUMNUMBERS="N_total" SWEEPS=8 NUMBER_EIGENVALUES=1 {MAXSTATES=100} I produce parbh.in.xml and then I run sparsediag getting a proper ground state energy (checked independently outside alps) -1.457060131536948 I use DMRG on the same input file obtaining LOWER eigenenergy... -1.6132399980266807 the result is little dependent on SWEEPS. MAXSTATES (which are rather large) and is obviously incorrect. I must be doing something wrong but what is it? Help welcome Thanks in advance, kuba -- Jakub Zakrzewski Zakład Optyki Atomowej Instytut Fizyki im. M. Smoluchowskiego ul. Reymonta 4, 30-059 Kraków, Poland +48-12-6635555, fax +48126338494 http://chaos.if.uj.edu.pl/~kuba

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eigenvectors of ED
by Bo-Nan JIANG 01 Apr '13

01 Apr '13

Hi, all I find in the ALPS tutorials of ED that "The output file now contains all the eigenvectors ". What does it mean? Does it mean that I could know all eigenvectors with respect to the corresponding eigenvalues? If it is ture, then what is the basis of eigenvectors? And how can I access to the eigenvectors ('cause I find none in the output xml files)? Bo-Nan -- Stay foolish,Stay hungry.

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