Recent Posts

1

General Questions and Discussion / MCTDHX forum will be shut down on February 11th 2024

« Last post by paolomo on February 06, 2024, 12:47:06 PM »

Dear users,
please note that this forum will be definitively closed down on February 11th 2024. Our entire MCTDH-X community has moved to Discord for instant messaging and discussion threads: https://discord.gg/CmEstjWE .

Many thanks,
Paolo for ultracold.org

2

General Questions and Discussion / IMPORTANT: Moving the MCTDH-X forum to Discord

« Last post by rui_lin on May 10, 2023, 06:19:37 PM »

Dear all users of the MCTDH-X forum,

we will soon close down this forum by this summer (2023), and will move our discussions to Discord.
You are very welcome to join our MCTDH-X community on Discord by the following link:

https://discord.gg/aQ4qYTV4Cx

Sincerely,
MCTDH-X team

3

General Questions and Discussion / Re: Errors encounterd during Installation

« Last post by Rohit Panda on April 05, 2023, 12:59:59 PM »

Hello,

I made use of the functionality implemented in the file /External_Software/External_Software.cmake available in the branch "FftwBlasLib" in the "MCTDH-X" gitlab repository.
The installation ran flawlessly and the MCTDH-X software is now working perfectly on my machine.

I extend my Thanks for your support.

Warmest Regards,
Rohit Panda

4

General Questions and Discussion / Re: Errors encounterd during Installation

« Last post by rui_lin on March 24, 2023, 01:52:34 PM »

Hi Rohit!

We have very recently implemented this functionality in the branch "FftwBlasLib" in the "MCTDH-X" gitlab repository. You can realize the mentioned functionality in the file /External_Software/External_Software.cmake. There should be detailed instruction in the file.

Please tell me if anything is unclear.

5

General Questions and Discussion / Re: Errors encounterd during Installation

« Last post by Rohit Panda on March 06, 2023, 06:30:07 AM »

Hello,

I have tried reinstalling the FFTW and BLAS. But I get the same errors as mentioned.
The BLAS and FFTW folders have been generated (extracted) in the "External Software" folder.
I think the error is encountered during the step " Performing build step for 'project_openblas' ".
Can you guide me on how to not link against FFTW ( if the problem is associated with FFTW) or specify CPU target for openBLAS ( if the problem is associated with BLAS).

I have also attached 2 screenshots of the lines in terminal right before the error is encountered.
Any help would be greatly appreciated.

Thank You,
Rohit Panda

6

General Questions and Discussion / Re: Errors encounterd during Installation

« Last post by mctdhb on February 25, 2023, 09:13:23 AM »

Hi there,

do you know at which step in the build process this error appears?

It looks like FFTW to me, but I am not sure.
Can you verify if this please (check if the FFTW and/or openblas were generated)?

For FFTW: if you have this from your Linux distro you have to make sure that you do not link against it, because the binary libraries in the distribution lack headers required for linking to Fortran.

For Openblas: might be required to specify a CPU target or upgrade the build to the latest version.

Hope that helps

7

General Questions and Discussion / Errors encounterd during Installation

« Last post by Rohit Panda on February 25, 2023, 08:57:48 AM »

Hello folks,

After running the installation file (Install_MCTDHX.sh) and selecting option 1 (FFTW+OpenBlas+GCC+mpif90) which is applicable for my machine, I get the following errors:

error: inlining failed in call to ‘always_inline’ ‘_mm256_extractf128_ps’: target specific option mismatch
error: inlining failed in call to ‘always_inline’ ‘_mm256_castps256_ps128’: target specific option mismatch
error: inlining failed in call to ‘always_inline’ ‘_mm256_hadd_ps’: target specific option mismatch
error: inlining failed in call to ‘always_inline’ ‘_mm256_hadd_ps’: target specific option mismatch

I have also attached a screenshot of the errors.
Any help would be greatly appreciated.

Thank you,
Rohit Panda

8

General Questions and Discussion / Re: Maximum number of particles for MCTDHB

« Last post by mctdhb on September 03, 2020, 09:34:31 AM »

Hi Asaad Sakhel!

The accuracy of MCTDH-B is dependent on the physical situation that is considered.
The size of the configuration space is N+M-1 choose N ; so for N=2000 particles you can work at most with M=3 orbitals.

If these 2003001 configurations would be a sufficiently large configuration space for the system you have in mind, then yes.

For instance, I think you could get a very accurate representation for harmonically, double-well, and triple-well trapped particles.
There exist many examples where MCTDH-B has been applied for N>200, for instance:

https://www.pnas.org/content/109/34/13521
https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.106.240401
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.100.130401

Best,
Axel

9

General Questions and Discussion / Maximum number of particles for MCTDHB

« Last post by asakhel on August 22, 2020, 12:34:15 AM »

Dear all,

  I just wanted to ask if MCTDHB can handle calculations with N=2000 particles
in three dimensions, like in a quasi-1D cigar trap. I know for example some
methods cannot handle more than 200 particles, etc.

Thank you
--Asaad Sakhel

10

Main Program Usage / Re: Default choice of the starting orbitals

« Last post by mctdhb on February 28, 2020, 02:02:48 PM »

Hi chrisapo!

Questions are always appreciated! Sorry for the delayed reply.

Regarding: the random choice of initial conditions
The algorithm to compute ground states via imaginary time propagation of the MCTDH-X working equations is generally very insensitive to the choice of initial conditions.

However, there are some pitfalls. For instance, when initial state (determined by coefficients and orbitals) has exactly zero overlap with the ground state that is sought.

The motivation for the random choice of initial conditions is to guarantee that the overlap with any possible state is finite. This random choice typically makes the initial steps of the integration a bit slower.

Regarding orthonormality: the orbitals (working as well as natural) should always be strictly orthonormal. For hand-given-orbitals, this is ensured by a Gram-Schmidt orthonormalization.

During real-time evolution, orthonormality is a property that follows from the projection operator in the equations of motion and the unitarity of the Hamiltonian.

During imaginary-time evolution, the orthonormality is guaranteed by a Gram-Schmidt orthonormalization at every integration step.

Hope that helps!