:orphan:

Counting the RelCC memory consumption
=====================================

It is of great importance to know the exact number of
the memory needed for a high memory and time demanding  RelCC job.

SCF
---
The first step is the SCF run with saving  molecular orbitals, preferably as DFPCMO text file.
Afterwards, using obtained molecular orbitals, prepare the active space for MOLTRA and RelCC.

MOLTRA & RelCC
--------------
Equip the MOLTRA input with the :ref:`MOLTRA_.NO4IND` keyword and RelCC input with the :ref:`RELCC_.COUNTMEM` keyword.
Run SCF part with previously saved converged molecular orbitals, with one iteration. 
The job passes quickly through MOLTRA integrals transformations as it produces only
two-index quantities in the MRCONEE file.

In the RelCC module, the program counts the memory need and leaves. 

Example
-------

Demonstration of this feature is in the DIRAC *test/count_cc_memory*, see
:download:`test  <../../../../test/count_cc_memory/test>`

We found the almost minimal setting - via the *--ag* parameter flag -  for the memory counting run:

::

 pam --noarch --gb=0.20 --ag=0.366 --inp=H2O.ae4z.x2c.scf_countmem-relcc.inp  --mol=H2O.xyz --put "DFPCMO.H2O.x2c.ae4z=DFPCMO" 

Input files are :download:`H2O.ae4z.x2c.scf_countmem-relcc.inp  <../../../../test/count_cc_memory/H2O.ae4z.x2c.scf_countmem-relcc.inp>`, :download:`H2O.xyz  <../../../../test/count_cc_memory/H2O.xyz>`, producing the output 
:download:`file  <../../../../test/count_cc_memory/result/H2O.ae4z.x2c.scf_countmem-relcc_H2O.out>`.

We are to look the "Peak memory usage" to get reasonable estimate of dynamic memory:

::

 Predicted RelCC memory demand:           0.335 GB
 Peak memory usage    (Gb) :   0.363

Next step is the sharp run based on the previous RelCC memory conuting.
The serial job
needs at least 0.366 GB, rounding to 0.4 GB of the total memory:

::

 pam --noarch --gb=0.20 --ag=0.366 --inp=H2O.ae4z.x2c.scf_relcc.inp  --mol=H2O.xyz --put "DFPCMO.H2O.x2c.ae4z=DFPCMO"

We also perform the parallel run, which
consumes at least 16*0.366 = 5.856 GB of the memory, rounding to 5.9 GB.
This amount of  memory must be free at the running machine equiped with at least 16 CPUs:

::

 pam --noarch --mpi=16 --gb=0.20 --ag=0.366 --inp=H2O.ae4z.x2c.scf_relcc.inp  --mol=H2O.xyz --put "DFPCMO.H2O.x2c.ae4z=DFPCMO"  

Have a look at the 
:download:`output  <../../../../test/count_cc_memory/result/H2O.ae4z.x2c.scf_relcc_H2O.out>` file.
We search there the peak memory usage which is cca 99.2% of the *--ag* parameter.

::

 Predicted RelCC memory demand:        0.335 GB
             Peak memory usage:        0.363 GB

Therefore in practical RelCC memory demanding calculations watch for the **Peak memory usage** value and set the **--ag** parameter
accordingly. This may take few iterations, especially when you want to find the real memory minimum.  
Don't forget to multiply your memory amount with the number of threads in parallel calculations.