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Changing code in spinmc
by Kourosh Sartipi 17 Dec '12

17 Dec '12

Hi everyone. We wanted to change the code to do some more calculations for nearest neighbor in spinmc. So far I've tracked down the problem to the file alps/applications/mc/spins/localupdate.h. We've also added the edge type for nearest neighbour in xml file defining the unit lattice. The problem is that getting edge type for the graph always returns zero. Can you please help me find our how should we track down the problem? Getting the edge type would be like this: int edgeType = boost::get(alps::edge_type_t(), graph, *iter); // iter is out_edge_iterator but the return value is always zero. (executing the exact same code for when the library parses the xml file produces the correct results. namely in file alps/src/alps/lattice/unitcell.c) Yours, Kourosh

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Worm algorithm and Green's function measurement
by Francisco Cordobés 16 Dec '12

16 Dec '12

Dear All, I have a question about the ALPS implementation of the Worm algorithm. In every paper I read about the Worm algorithm the same idea pervades: the Worm algorithm can easily sample Green's function(in imaginary time) because the movements of the worm do precisely that. Or in other words, Green's functions can be measured by histogramming the relative position of the head and tail of the worm(adding a 1 to the G(i-j,tau2-tau1) entry whenever the head is at i,tau2 and the tail is at j,tau1). The current version of the ALPS Worm code(alps 2.1) does not measure Green's functions and the issue was discussed, albeit briefly, earlier this year in a couple of e-mails, and it was mentioned that it would actually be too costly computationally to get all the N^2 values and only the relative distances would be measured. Is it because of the computational time needed in the Green's function configuration space would be too long and the current implementation samples mostly the partition function configuration space(by shifting/moving closed loops)? Or is it due to some technical detail that is usually not mentioned in the papers?(or that I might have not understood it correctly). Cheers, Francisco Cordobes

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meaning of sweep and thermalization
by Sara Ghadiri 14 Dec '12

14 Dec '12

Dear friends Sorry I have 2 question: 1) Would you mind explaining me that what is exact meaning of "sweep" and "thermalization" and "update" in your classical montecarlo? 2) My other question is that , how can be sure that my system in my program will arrive to thermal equilibrium and after that the plot will be written?I mean what numbers should I choose for sweep or thermalization?

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DMRG for 2D systems
by jessica.alfonsi＠unipd.it 14 Dec '12

14 Dec '12

Dear ALPS users and developers, is it possible to use the DMRG application in ALPS for two-dimensional systems (with not too many sites), like for instance two-leg ladder models, or is it necessary to implement additional the code ? Best regards, Jessica Alfonsi

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DMRG slow convergence
by Emanuele Levi 12 Dec '12

12 Dec '12

Dear ALPS developers and users, I am using the DMRG algorithm to check the entropic properties of the ground state of an Heisenberg chain. More specifically in the region Jx=Jy=1 and Jz>1 , which is a gapped region. I sweep until I see that the entanglement entropy repeats on a certain pattern through next sweeps. At that stage the simulation should have converged on a good approximation of the ground state, and I take my data. For systems close to the critical point (e.g. Jz=1.001) the results I get are comparable to exact results, and everything works perfectly. When I increase the gap though, I manage to get sensible results only on very short chains. To explain you what happens on longer chains I am attaching to this mail a plot of the entropy against the iterations. This picture refers to Jx=Jy=1 Jz=2.5 L=42 Nstates=400 Nsweeps=40 periodic boundary conditions As you can see it struggles to converge to a sensible value. This picture isa goodrepresentative of any simulation I run. There are two features I see: 1- jumps from a lower value to an higher one: I think this could be explained with the fact that as the system sweeps, it gets short range correlations and it converges immediately to another ground state. 2- the slow convergence in the final stage to a sensible value. This I really don't know how to explain. Do you know what is going on, and how could I enhance the simulation? Just increasing the number of sweeps or there is a smarter way in your opinion? (It looks like increasing the states kept doesn't change too much the situation, and I really need periodic boundaries for the kind of plot I want to produce). Many thanks again for your precious help. Kindest regards. -- Emanuele Levi emanuele.levi(a)gmail.com

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what is the classic monte carlo algorithm?
by sh sh 12 Dec '12

12 Dec '12

Dear friends Would you mint telling me what is the classic MC algorithm in codes of alps python? And , Is the "T" in units of J/KB , in the plots which are versus T, forexample sprcific heat ? thanks for your help

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maxent
by dt331＠bath.ac.uk 12 Dec '12

12 Dec '12

Dear All, I would like to attempt the analytic continuation of greens function produced by TRIQS to obtain the spectral function. I have installed the maxent tool, but can not find how to use it. Can anyone show me some example input files and other information on its functioning? A reference on the method would also be useful. Thanks, David Tompsett.

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help for one code
by sh sh 08 Dec '12

08 Dec '12

Hi friends.I am practicing tutorial and I faced one code for doing one plot with all data like this: #load the binning analysis for the absolute value of the magnetization binning = pyalps.loadBinningAnalysis(pyalps.getResultFiles(prefix='param'),'|Magnetization|') binning = pyalps.flatten(binning) #make one plot with all data for dataset in binning: dataset.props['label'] = 'L='+str(dataset.props['L']) plt.figure() plt.xlabel('binning level') plt.ylabel('Error of |Magnetization|') pyalps.plot.plot(binning) plt.legend() plt.show() Now I have 2 question: 1. I can not understand what is the meaning of : " dataset.props['label'] = 'L='+str(dataset.props['L'])",what is its meaning? 2. And also if I wanna plot energy versus temperature , which part of the above code must be changed ? thanks alot for your help

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question for extracttext
by sh sh 07 Dec '12

07 Dec '12

Hi friends.I am learning working with alps so I test the codes that is written in website for classic monte carlo simulation.I wrote those codes on my terminal but when I arrive to codes below: extracttext plot.xml parm2a.task*.out.xml extractxmgr plot.xml parm2a.task*.out.xml > plot2a.xmgr xmgrace plot2a.xmgr it gives error and in my terminal it said that /opt/alps/bin/xslttransform: 16: exit: Illegal number: -1 /opt/alps/bin/xslttransform: 16: exit: Illegal number: -1 /opt/alps/bin/xslttransform: 16: exit: Illegal number: -1 so what shoul i do? also how can I install xmgrace for the above code?

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question
by sh sh 07 Dec '12

07 Dec '12

Hi friends,sorry when I run "extracttest" program , I face the error that say: Could not find XSLT transformer. Please set the ALPS_XSLT_TRANSFORMER environment variable what does it mean?what can I do?

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