September 2012 - Comp-phys-alps-users

Inconsistent comment in generate_spline_matrix in the DMFT folder
by Kuangshing Chen 21 Jul '15

21 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

ALPS 2.0.1 released
by Matthias Troyer 19 Sep '12

19 Sep '12

Dear ALPS users, ALPS 2.0.1 has been released. This is the version included with the ALPS paper: B. Bauer et al., J. Stat. Mech. (2011) P05001, which is available at : http://www.iop.org/EJ/abstract/1742-5468/2011/05/P05001 .Besides references to this paper, this release contains many minor bug fixes. The MacOS X 10.5 binary release will be uploaded shortly. The others are ready for download. Best regards Matthias Troyer

4 33

questions about worm code
by Lev 18 Sep '12

18 Sep '12

Dear Dr. Troyer and users of ALPS, I am trying to measure local magnetization with MEASURE_LOCAL[Local magnetization]=Sx for the following model: <HAMILTONIAN name="my spin model 1"> <BASIS ref="spin"/> <SITETERM site="i"> -2*xi*Sz(i)-2*h*Sx(i) </SITETERM> <BONDTERM source="i" target="j"> -g*(Splus(i)*Sminus(j)+Sminus(i)*Splus(j)) </BONDTERM> </HAMILTONIAN> Value of parameter xi depends on the site in an actual problem, but this is not important now. Since dirloop_sse says that "Offdiagonal site terms are not implemented in this SSE code", I use the worm code. Worm code says the following for this: "Will not measure "Local magnetization" since it is off-diagonal or not a site operator". As a trick to overcome this problem, I tried to rotate the coordinate system in order to measure the required values with MEASURE_LOCAL[Local magnetization]=Sz In this case the rotated model is: <SITEOPERATOR name="Sy" site="x"> 1/2/I*(Splus(x)-Sminus(x)) </SITEOPERATOR> <HAMILTONIAN name="my spin model 2"> <BASIS ref="spin"/> <SITETERM site="i"> -2*xi*Sy(i)-2*h*Sz(i) </SITETERM> <BONDTERM source="i" target="j"> -2*g*Sz(i)*Sz(j)-2*g*Sx(i)*Sx(j) </BONDTERM> </HAMILTONIAN> Now the worm code says the following: "can not convert complex number into real one". Therefore, the worm code does not seem to understand Sy(i) as a site term in Hamiltonian (?). Finally, I tried another version of rotation, which also would allow to measure with MEASURE_LOCAL[Local magnetization]=Sz The rotated model is: <SITEOPERATOR name="Sy" site="x"> 1/2/I*(Splus(x)-Sminus(x)) </SITEOPERATOR> <HAMILTONIAN name="my spin model 3"> <BASIS ref="spin"/> <SITETERM site="i"> 2*xi*Sx(i)-2*h*Sz(i) </SITETERM> <BONDTERM source="i" target="j"> -2*g*Sz(i)*Sz(j)-2*g*Sy(i)*Sy(j) </BONDTERM> </HAMILTONIAN> Now the worm code says the following: "Cannot simulate this bond term with the worm code". Therefore, the worm code does not seem to understand Sy(i)*Sy(j) as a bond term in Hamiltonian (?). Could you let me know whether there are ways to perform the measurement ? Sincerely yours, Lev Barash

2 1

Dynamical quantities with ALPS ED
by Mykola Maksymenko 13 Sep '12

13 Sep '12

Dear everybody, I am curious I it is possible to write a function in ALPS ED code to calculate the dynamical responses in a spectral representation ? It seems like in a simplest case one can compute it directly by having access to the matrix elements of the operator and corresponding energy eigenvalues of the Hamiltonian. Isn't it ? Will be thankful for the answer! With best regards, Mykola

1 0

Binary installation of ALPS at an alternative location in windows
by Chao Shen 09 Sep '12

09 Sep '12

Hi all, I try to install ALPS binary in a position other than 'C:\program files' because there I would need administrator privilege to create files, etc. I noticed on ALPS website it says I just need to set environment variable ALPS_XML_DIR to point to the position of the actual XML directory, e.g. 'E:\ALPS\lib\xml'. However this doesn't really have any effect. When I run 'tutorial1a.py' which calls 'spinmc.exe' in the tutorial folder, 'spinmc.exe' complains about missing 'lattice.xml' at location 'C:\program files\ALPS\lib\xml'. Apparently the environment variable ALPS_XML_DIR didn't take effect at all. I am wondering if this is a bug or there are actually other environment variables to set? Thanks in advance. Yours, Chao

1 0