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A Few Questions about the DMRG code.
by T.J.Hewitt 13 Jan '16

13 Jan '16

Dear All, I'm currently using the ALPS DMRG algorithm to calculate energy eigenvalues for a given quantum model. After running many simulations and analyzing the results I have a few questions that I'm hoping you can answer. 1) The lattice model I'm looking at is an open ladder with 2-legs. Is the DMRG code supplied in ALPS capable of correctly handling such a lattice configuration? 2) I've also noticed that the results from these DMRG simulations are non-deterministic, that is the result is only consistent to a specific decimal point every run, given the same input parameters. Other DMRG programs I have used previously gave deterministic results given the same input parameters. I'm assuming that the inconsistency of the ALPS DMRG results is due to the utilization of the Lanczos algorithm to calculate the energy eigensets on each run. Can someone confirm that this is the case? Additionally, I have tried changing the 'LANCZOS_TOLERANCE' parameter, which I'm assuming would give better and more consistent results, but this has no effect on the results. Given that my assumption is correct what is the proper way to code this input parameter. Thanks, Tyler Hewitt

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measure correlatons use mps codes
by 北尘心 06 Jan '16

06 Jan '16

Hi, I want to measure corrections by mps code.I use the command like MEASURE_HALF_NN_CORRELATIONS[A]="cdag_up:cdag_down:c_up:c_down". but it unable to calculate the following situtation: "cdag_up:cdag_down:c_up:c_down|(0,1,1,2)".How can i acheieve it? Thank you very much if you could give me any advice . Best, Xinbo Wei

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ALPS DWA - Moving to C++11/ 14
by Tama Ma - Yotcopi 06 Jan '16

06 Jan '16

Dear ALPS community, Is there anyone who is strongly against using C++11/ 14 for ALPS DWA development? Also, if you have any desirable requirements from the physic community, please kindly drop me your comments here. Thank you very much. Best regards, Tama MA

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Question on time series and autocorrelation time
by Leo Fang 20 Dec '15

20 Dec '15

Hello, After the Monte Carlo simulation is done, the time series as well as the autocorrelation time (tau) for each observable are recorded in the path /simulation/results/ of the hdf5 file. (For example, /simulation/results/observable/timeseries/data gives the time series.) I have two questions: 1. What determines the length of the time series array? In my experience its typical size is around 100. How does ALPS decide to cut the array? 2. If the binning method is not specified, what's the default way of calculating tau? I've tried to calculate the integrated autocorrelation time using the recorded time series, but it's not exactly same as tau given by ALPS. Thank you. Sincerely, Leo (Fang Yao-Lung) Duke Physics

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About the stiffness in Direct loop QMC
by 郭怀明 20 Dec '15

20 Dec '15

Dear All, I have a question about the stiffness measured in direct loop QMC. I consider hard-core bosons, when the stiffness is the superfluid. I find its defination: <W^2_x+W^2_y>/2t\beta L, where W_x(y) is the winding number along the x or y direction. Suppose I have square lattice. If next nearest neighbor hopping is included with amplitude t', is its contribution is included in the code? Also if the lattice is two-leg ladder with NN and NNN hopping (the amplitudes are t and t'), the superfluid is along one direction. Is the contribution from the NN and NNN hoppings included? Sincerely, Huaiming Guo

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About the measurement in direct loop QMC
by 郭怀明 20 Dec '15

20 Dec '15

Dear all, I want to ask a question about the measurement in direct loop QMC. 1: can we use "Measure[Bond type stiffness]=True " for hardcore bosons? Since I use it, no result is returned. 2: If I use " MEAURE_FACTOR[Name]="n" " to measure the stucture factor, the error appears. Does QMC not support such expression? 3: When I measure the structure factor, are the structure factor with all possible momentum provided? Can I specify the wanted momentum, such as: 2\pi/3 for 1D? Thank you very much. Sincerely, Huaiming Guo

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Defining a complex operator in model.xml file for alps_mps_optim
by Henry Otobrise 08 Dec '15

08 Dec '15

Dear users, I need to use the Alps_mps_optim code to compute the expectation values of some complex operators e.g. string and parity operators. However, after modifying the model.xml file to define the operator of interest (following Michele Dolfi's earlier suggestion), I kept getting error messages indicating that I must have done somethings wrong in the model.xml file. Below is the relevant portion of the model.xml file that includes the modifications made by me: <SITEBASIS name="boson"> <PARAMETER name="rho" default="1" /> <PARAMETER name="theta" default="pi" /> !my modification <PARAMETER name="Nmax" default="infinity" /> <QUANTUMNUMBER name="N" min="0" max="Nmax" /> <OPERATOR name="bdag" matrixelement="sqrt(N+1)"> <CHANGE quantumnumber="N" change="1" /> </OPERATOR> <OPERATOR name="b" matrixelement="sqrt(N)"> <CHANGE quantumnumber="N" change="-1" /> </OPERATOR> <OPERATOR name="n" matrixelement="N" /> <OPERATOR name="n2" matrixelement="N*N" /> <OPERATOR name="dn" matrixelement="rho-N" /> <OPERATOR name="strireal" matrixelement="cos(theta*(rho-N))" /> !my modification <OPERATOR name="strimag" matrixelement="1j*sin(theta*(rho-N))" /> !my modification <OPERATOR name="string" matrixelement="cos(theta*(rho-N))+1j*sin(theta*(rho-N))" /> !my modification </SITEBASIS> Following is the result produced by the attempt to run the code with the modifications: Running task 1. This binary contains symmetries: nu1 MAQUIS repo r4143 Temporary storage enabled in /home/henry/Documents/ALPS_TEMP_DATA/storage_temp_ad178b56d3f6/ Restoring state. Will start again at site -1 in sweep 16 Exception thrown: Did not parse to end of string 'cos(theta*(rho-N))+1j*sin(theta*(rho-N))' henry@TheoreticalPhys-OAU:~$ The code ran when the "string" operator definition is removed, so that I believe that the problem is with my definition of the "string" operator. I will appreciate any assistance to help solve this problem. Thank you and best regards. Henry Otobrise, Dept. of Physics and Engineering Physics OAU, Ile-Ife, Nigeria.

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Weird error when compiling ALPS as a release build on Linux
by Leo Fang 04 Dec '15

04 Dec '15

Hello all, I used the following command to build the ALPS 2.2.0.b3 library (with Boost source code): cmake \ -D ALPS_BUILD_TESTS=OFF \ -D ALPS_BUILD_EXAMPLES=OFF \ -D ALPS_BUILD_APPLICATIONS=ON \ -D ALPS_BUILD_PYTHON=ON \ -D LAPACK_64_BIT=ON \ -D Boost_ROOT_DIR=/home/yf30/alps-2.2.b3-r7462-src-with-boost/boost/ \ -D CMAKE_BUILD_TYPE=Release \ -D CMAKE_INSTALL_PREFIX=/home/yf30/alps/ \ -D CMAKE_C_COMPILER=/usr/bin/gcc \ -D CMAKE_CXX_COMPILER=/usr/bin/g++ \ -D ALPS_ENABLE_MPI=ON \ -D MPI_CXX_COMPILER=/usr/lib64/openmpi/bin/mpicxx \ -D MPI_C_INCLUDE_PATH=/usr/include/openmpi-x86_64/ \ -D MPI_C_LIBRARIES="/usr/lib64/openmpi/lib/libmpi.so;/usr/lib64/openmpi/lib/libopen-pal.so;/usr/lib64/openmpi/lib/libopen-rte.so" \ -D MPI_CXX_INCLUDE_PATH=/usr/include/openmpi-x86_64/ \ -D MPI_CXX_LIBRARIES="/usr/lib64/openmpi/lib/libmpi_cxx.so;/usr/lib64/openmpi/lib/libopen-pal.so;/usr/lib64/openmpi/lib/libopen-rte.so" \ /home/yf30/alps-2.2.b3-r7462-src-with-boost/alps/ However, when I execute the hybridization solver, the program terminates with the following error message: (input parameter omitted) Hybridization Expansion Simulation CT-HYB Part of the ALPS DMFT Project Usage requires citation of the ALPS CT-HYB paper and the ALPS paper Refer to the documentation for more information. process 0 of total: 1 starting simulation in dgesv: info was not zero. After a lot of trials and errors, I found that if I set "CMAKE_BUILD_TYPE=Debug" when building ALPS, this error does not show up and I do get correct results. I thought the only difference between a debug build and a release build is that the former has an extra "-g" flag to include debug symbols. Why would the lapack function dgesv be wrong? Thanks. Sincerely, Leo (Fang Yao-Lung) Duke Physics

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spin correlations in classicla ALPS simulations
by D´Souza, Sunil Wilfred 04 Dec '15

04 Dec '15

Dear ALPS users, I am trying classical Monte Carlo simulations using the executable (spinmc) by considering the 3D Heisenberg model. I am interested in studying the spin correlation functions. In this regard, I was searching for the key word by using which i will be able to obtain the spin correlation data. but i have not come across any key words related to the spin correlation measurements in the classical case of the ALPS simulations. Henceforth, I am very kindly requesting you to let me know that is it possible to determine the spin correlations by using the spinmc executable and if so please provide me with the necessary details. I am eagerly looking forward for your valuable suggestions.I thank you in advance for your time and consideration with best regards Sunil

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About the Green function in QMC
by 郭怀明 02 Dec '15

02 Dec '15

Dear All, I have a question regarding measuring Green function in QMC with directed loop update. In my understanding, the green function is the average G_{i,j}=<b^\dagger_i b_j>. If i=j, G should equal the local density. However it turns out that they are not equal. I wonder what is wrong with my understanding. I appreciate the replies. Sincerely, Huaiming Guo

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