October 2012 - Comp-phys-alps-users

Inconsistent comment in generate_spline_matrix in the DMFT folder
by Kuangshing Chen 22 Jul '15

22 Jul '15

Hi, The function generate_spline_matrix in fouriertransform.C in the dmft folder shows the comments as follows: // A is the matrix whose inverse defines spline_matrix // // 6 6 // 1 4 1 // 1 4 1 // A = ... // // 1 4 1 // -2 0 0 2 However, the following codes, dense_matrix A = 4*dt/6.*boost::numeric::ublas::identity_matrix<double>(Np1); for (int i=1; i<Np1-1; i++) { A(i,i-1) = dt/6.; A(i,i+1) = dt/6.; } A(0,0) = 1.; A(0, Np1-1) = 1.; A(Np1-1, 0) = -2.*dt/6.; A(Np1-1, 1) = -1.*dt/6.; A(Np1-1, Np1-2) = 1*dt/6.; A(Np1-1, Np1-1) = 2*dt/6.; the red lines will make the matrix looks like // 6 6 // 1 4 1 // 1 4 1 // A = ... // // 1 4 1 // -2 *-1* *1* 2 Is the comment correct or the code correct? Any reference for this algorithm? Thank you, Kuang-Shing Chen

5 25

question about sparsediag
by 陈巧妮 01 Jan '13

01 Jan '13

Hi, everyone When I use sparsediag to diagnalize the Hamiltonian of Hubbard model, the paprameter is : CONSERVED_QUANTUMNUMBERS="Nup,Ndown" Nup_total=6 Ndown_total=6 the system size is L=12, no translation symmetry here, the process will take 100s, which is much slower than our own Davison code(It only take 20s). if I add the measurements MEASURE_ENERGY="True" MEASURE_LOCAL[density]=n MEASURE_LOCAL[double occupancy]=U*double_occupancy MEASURE_CORRELATIONS[density matrix_up]="cdag_up:c_up" MEASURE_CORRELATIONS[density matrix_down]="cdag_down:c_down" the process will take 900s. Does anyone know how to speed up this calculation? Or at least avoid the waste time on the measurements -- Qiaoni Chen Department of Chemistry, Princeton University Princeton, NJ, 08544 Tel +1-609-865-0817

2 1

Edit Complex number
by Forwordom 30 Oct '12

30 Oct '12

2 1

How can we visualize a lattice in ALPS?
by kaveh edalat 30 Oct '12

30 Oct '12

Dear All I want to make a new lattice, but before serious calculation, I like to see the lattice. I searched in the alps mailing list and I found that probably "lattice-preview" should be a tool for visualization of lattices in ALPS. But I have two problem: first, when simply I type "lattice-preview" in the terminal I receive the following error: /opt/alps/bin/lattice-preview: 30: /opt/alps/lib/python/alps/preview.py: Permission denied Is there anyone to know why I receive the error? second, If we suppose the "lattice-preview" works well, what is the input file for this program? thanks in advanced Kaveh Edalat

2 1

Covariance matrix of RealVectorObservable
by Giuseppe Carleo 29 Oct '12

29 Oct '12

Dear all, I have got a question about the calculation of the covariance matrix of a vector observable (RealVectorObservable type, for example): Indeed I am able to compute the (jacknife-corrected) simple covariance of two given scalar observables in this simple way --------------- string filename = "simulation.task1.out.h5"; mcdata<double> obs1; mcdata<double> obs2; obs1.load(filename, "simulation/results/" + alps::hdf5_name_encode("Observable1")); obs2.load(filename, "simulation/results/" + alps::hdf5_name_encode("Observable2")); cout << "Covariance: " << obs1.covariance(obs2) << "\n\n"; --------------- However it is not entirely clear to me how to proceed when one instead has a single vector observable recorded in the hdf5 file and wants to compute to covariance matrix of its entries. In that case mcdata cannot be used any longer and digging into the code source I did not manage to find a method "covariance" implemented for other than mcdata-like scalar observables. Is there a handy solution already implemented for that? Thank you in advance! Regards, Giuseppe

1 0

Re: [ALPS-users] Comp-phys-alps-users Digest, Vol 79, Issue 6
by Forwordom 29 Oct '12

29 Oct '12

2 1

Edit Complex number
by Forwordom 28 Oct '12

28 Oct '12

Hi alps users and developers I want to simulate a lattice phase transition in external magnetic along x,y,z direction by using dmrg.I have to couple site operator with external magnetic field. But how to edit a complex number in the ALPS models.xml to get site operator Sy=1/2i(Splus-Sminus). Thanks in advance for your reply.

2 1

Imaginary Operators and advanced correlation functions
by zhian asadzadeh 27 Oct '12

27 Oct '12

Dear ALPS users, I have two questions regarding DMRG application of ALPS; 1. is it possible to define imaginary operators in this new version? in the simplest case I tried for operator like Sy=1/(2*I)(S+-S-) and it seems doesn't recognise I, how should i define the imaginary part? 2. I am interested to calculate correlations like <O1O2O3> in which O's are local operators and they could be also imaginary like Sy in (<Sx(i)Sy(j)Sz(k)>? I know at the moment just correlations like <O1O2> are calculable, but I would like to know is it easy to implement the above mentioned problem or is there a kind of trick to do it? -- Sincerely yours, Zhian.

1 0

spinmc questions
by Jonas Anderson 22 Oct '12

22 Oct '12

I have some very basic questions for which I cannot find documented answers. (1) For the Ising models or more generally for classical spin models is it possible to view the final spin configuration of a system after the simulation has run its course? (2) Is it possible to observe the magnetization and not just the absolute value of the magnetization? Thanks in advance, -jonas -- Jonas T. Anderson Post-doc Université de Sherbrooke

2 3

tmp directory for DMRG
by benoît grémaud 19 Oct '12

19 Oct '12

Dear All, I would like to know if one can change, at runtime, the directory for temporary files used by the DMRG code. /tmp is the current location, but my / partition is rather small and get filled rapidly for large system sizes. thank you for your help. (i am using alps-2.1.1-r6176) regards, Benoît Grémaud -- -------------------- Researcher at CNRS, Laboratoire Kastler Brossel (Paris, France) Visiting Associate Professor at the Centre for Quantum Technologies (NUS, Singapore)

3 3