Recent Posts

21

Main Program Usage / Re: Estimation of Memory in Relaxation.

« Last post by mctdhb on December 04, 2017, 09:18:03 AM »

Hi there!

The memory needed for a computation with MCTDH-B for the coefficients is (N+M-1 over N)*(16 bytes [double precision complex])*(Dimension of Krylov subspace used for the integrator). The size of the Krylov subspace is adaptive, i.e., it depends on the particular problem studied; but it can be controlled using the "Minimal_Krylov" and "Maximal_Krylov" inputs in the MCTDHX.inp file.

In addition, M*N_g*[O(10)]*(16 bytes [double precision complex]) of memory is needed for the solution of the orbital equation.

Regards,
Axel

22

Analysis Program Usage / Memory errors when Phase, Gradient = .T.

« Last post by yeongjingwak on November 27, 2017, 10:45:18 AM »

Hi,
Recently, I'm using the program in 1D.

When I run the analysis program, I found that the program gives several memory errors.

I wanted to find it myself, but I can't do it because I don't understand the program structure yet.

Would you give me any suggestion about these issues?



Error Messages are followings

(1) Memory Corruption
Before phase: T T F
*** Error in 'MCTDHX_analysis_gcc' : malloc(): memory corrupton: 0x~~~~~
======

(2) Memory Free (At the same place with (1))
free(): Invalid next size (fast): 0x~~

23

Main Program Usage / Estimation of Memory in Relaxation.

« Last post by yeongjingwak on November 27, 2017, 10:31:03 AM »

Hello, I joined this community 2 months ago.

I'm wondering how to estimate the memory capability of the computation.

When I run relaxation program, It seems that it mainly depends on the value (N+M-1 over N).

But the allocated memory scale grows much faster than that when I changed N and M values.

When other parameters are fixed, how does the allocated memory size depend on M and N?

24

General Questions and Discussion / MCTDH-X Synopsis

« Last post by mctdhb on May 09, 2017, 11:49:36 AM »

What MCTDH-X is and what it can do

MCTDH-X is a unique method that -- roughly speaking -- allows one to describe the way little particles behave according to quantum physics. The MCTDH-X software is an implementation of that theory that allows to compute and visualize these quantum dynamics. Specifically, it is a way compute some fundamental properties of ensembles of indistinguishable particles, that is gases of atoms, that are constrained in a box or container at extremely low temperatures or electrons in atoms or molecules.

These properties can be collective, i.e., followed by all (or almost all) particles of the system or not. In the former case one is talking about a Bose-Einstein condensate if the considered particles are indistinguishable bosons or uncorrelated fermions if the considered particles are indistinguishable fermions; in the latter case, the we speak about something more complicated, a so-called fragmented many-boson or a correlated many-fermion state. Indistinguishable bosons at low temperature or indistinguishable electrons in atoms or molecules behave quantum-mechanically: they are wave-like in nature and, hence, totally different than ordinary matter. In a Bose-Einstein condensate (BEC), for instance, all the indistinguishable particles of the gas behave as if they were single effective particle.

Quantum fluctuations and correlations are negligible -- such a behavior is referred to as coherent for bosons and single-configurational for fermions. However, there are many cases in which this not true, even at ultracold temperatures. Phenomena like fragmentation and  correlations become very important. In such cases MCTDH-X is applicable, but conventional mean-field descriptions fail. MCTDH-X is designed to solve many-body dynamics of small and intermediate systems of ultracold particles (bosons or fermions) and shed light at phenomena where correlations emerge and mean-field approaches break down.     

The fundamental physical equation that governs the evolution of atomic and quantum systems is the Schrödinger equation. MCTDH-X is a method that can, in principle, describe these quantum dynamics exactly, i.e., to any desired given numerical accuracy, for a wide range of scenarios. To see more details about the MCTDH-X method and software, just click here:  http://ultracold.org/menu/

25

Main Program Usage / Re: RungeKutta Error

« Last post by mctdhb on December 09, 2014, 09:51:48 AM »

Hello Andr?,

The problem you quote is with the integrator Runge Kutta of order 8 that you chose for the solution of the orbitals equations of motion. The energy and occupations seem to be undefined (NaN). In the future, please also post the input file "MCTDHB.inp" to make the analysis easier.

I think you specified the wrong file to read from, right? Anyways, I think we resolved this problem by renaming your *orbs.dat and *coefs.dat files?

I will take your post as a request to revise the input handling, especially, I would like to deprecate the restart from ASCII files with GUESS='DATA' in the near future.

Could you specify, what fixed the issue?

Regards,
Axel

26

Main Program Usage / RungeKutta Error

« Last post by andre_smaira on December 05, 2014, 09:56:34 AM »

Hello

I made a mistake (I don't know where) and all executions are returning this message:

RUNGEKUTTA order 8 Problem: Errorflag:         -51
 Time   1.5000000000000000E-003 Step   1.0000000000000000E-003 Energy                       NaN
 Difficulties in the inversion of the rhos.    Using simplified inversion for the rhos.
 Nocc(           1 )=0d0                       NaN
 Nocc(           2 )=0d0                       NaN
 Product of Rho*(Rho^(-1))                       NaN

Can someone help me?

Thank you
Andre

27

Main Program Usage / Re: Full CI

« Last post by mctdhb on June 20, 2014, 04:36:12 PM »

Dear Shachar,

FCI is basically operative, yes. If the Job_Type is set to 'FCI', either standard "Full CI" or Bose-Hubbard Hamiltonians can be treated.

What orbitals will be taken, depends on the input variable "Guess". If you set Guess to 'HAND', then the routine source/ini_guess_pot/Get_Initial_Orbitals.F will be executed to specify the orbitals of the initial guess, if Guess='BINR' ('DATA'), the program will restart with the orbitals in the PSI_bin file ( ASCII file with the filename you specified by Restart_Orbital_FileName) in the working directory.

After the initial guess' orbitals and coefficients are determined, a full CI computation is done -- that is, the coefficients are propagated in real or imaginary time.

Did that resolve your question?

Regards,
Axel

28

Main Program Usage / Full CI

« Last post by shachar on May 28, 2014, 12:27:15 PM »

Hello developers,

Should the FCI option work? I don't see any related printout when I set it.

Do I understand correctly that it should take the initial orbitals and just solve for the CI and give me the CI vector and energy of the given orbital set?

Thanks in advance.

best,
Shachar

29

Analysis Program Usage / R-MCTDHB Synopsis

« Last post by mctdhb on October 17, 2013, 11:50:07 PM »

The Recursive implementation of the multiconfigurational time-dependent Hartree for bosons

What is it?
A collection of programs and scripts to solve exactly the time-dependent many-boson Schr?dinger equation and visualize the obtained solutions. The numerical solution of the problem is obtained with an efficient, shared and distributed memory-parallelized Fortran program that can be used with bash scripts or through a graphical user interface. From the simulation's output, graphs and videos are generated by invoking bash scripts that use mencoder and gnuplot for the task.

How it is documented?
The usage of the program is documented in a user manual and the code is documented in doxygen-generated html pages containing call- and caller-graphs.

How is it managed?
The code is version managed by mercurial (hg).

What does it need?
The program package can be installed on any Linux/Unix-based system that has a bash-shell, GCC or Intel Fortran compilers, and LAPACK, FFTW, and/or Intel MKL.