Acceleration in CCSDT calculation

Dear MRCC developers,

I am running CCSDT calculations on small transition metal complexes using MRCC2019. I found that one iteration of CCSDT can take up to 8 hours for a system of 121 basis function. I know that CCSDT calculations are expensive but I am still wondering if I did something wrong to make it this slow. For example, if I could allocate more memory to reduce the file I/O on the disk? Below I attach the essential inputs of mine as well as the output file. Thanks in advance for your help.

Best,
Chenru

======input=======
calc=ccsdt
ovirt=off
rest=2
cialg=direct2
core=frozen
scftype=rohf
rohftype=semicanonical
dens=0
mem=64GB
usedist=1
mult=2
charge=2
===================

=======output========
Executing goldstone...

Generation of MRCC equations in terms of H and T...
Generation of antisymmetrized Goldstone diagrams...
Number of diagrams in T^1 equations: 15
Number of diagrams in T^2 equations: 37
Number of diagrams in T^3 equations: 47
Translation of diagrams to factorized equations...
Number of restricted diagrams in T^1 equations: 30
Number of restricted diagrams in T^2 equations: 126
Number of restricted diagrams in T^3 equations: 274
Optimizing intermediate calculation...
Number of floating-point operations per iteration step: 2.2488E+14
Probable CPU time per iteration step (hours): 2248.77
Required memory (Mbytes): 21353.1
Number of intermediates: 210
Number of intermediates to be stored: 100
Length of intermediate file (Mbytes): 49946.4

************************ 2020-02-16 12:47:24 *************************
Executing xmrcc...

**********************************************************************
MRCC( 3 ) calculation


Allocation of****** Mbytes of memory...
Number of spinorbitals: 246
Number of alpha electrons: 16
Number of beta electrons: 15
Number of active particles: 108
Number of active holes: 0
Spin multiplicity: 2
z-component of spin: 0.5
Spatial symmetry: 1
Convergence criterion: 1.0E-06
Construction of occupation graphs...
Number of 0 -fold excitations: 1
Number of 1 -fold excitations: 3332
Number of 2 -fold excitations: 4060650
Number of 3 -fold excitations: 2345138260
Total number of configurations: 2349202243
Calculation of coupling coefficients...
Length of intermediate file (Mbytes): 36278.4

======================================================================

Memory requirements /Mbyte/:
Minimal Optimal
Real*8: 36145.9237 36145.9237
Integer: 58.1929
Total: 36204.1166 36204.1166


************************ 2020-02-16 12:47:35 *************************
Executing mrcc...

**********************************************************************
CCSDT calculation


OpenMP parallel version is running.
Number of CPUs: 16
Allocation of36145.9 Mbytes of memory...
Number of spinorbitals: 246
Number of alpha electrons: 16
Number of beta electrons: 15
Number of active particles: 108
Number of active holes: 0
Spin multiplicity: 2
z-component of spin: 0.5
Spatial symmetry: 1
Convergence criterion: 1.0E-06
Construction of occupation graphs...
Number of 0-fold excitations: 1
Number of 1-fold excitations: 3332
Number of 2-fold excitations: 4060650
Number of 3-fold excitations: 2345138260
Total number of determinants: 2349202243
Calculation of coupling coefficients...
Initial cluster amplitudes are read from unit 16.
Length of intermediate file (Mbytes): 36278.4
Reading integral list from unit 55...
Sorting integrals...
Sorting integrals...
Sorting integrals...
Sorting integrals...
Energy of reference determinant [au]: -1557.177195858343
Calculation of MP denominators...

Starting CC iteration...
==========================

Dear Mihaly,

Thank you so much for your speedy reply. I will try playing around with the symmetry. In terms of using a machine of larger memory, I am wondering that now it seems only using 36204.1166 MB memory (I allocated 64 GB) and writing 36278.4 MB intermediate file. Do you think it will be accelerated if I use a machine with >73GB memory? Sorry I do not know whether I read the out file correctly and will be appreciated for your further help.

Best,
Chenru

Here is the out file. Thank you so much!

Chenru