MK-CCSD on Kogence isn't much faster as expected.


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Gets Around
Hello Nwchem users

I have following input

title "cubane CCSD/cc-pVDZ hessian"

memory stack 500 mb heap 500 mb global 22000 mb

geometry
 symmetry C2v
 H                     2.05734129    -1.32981120     0.02496974
 C                     1.09520984    -0.79607173    -0.03872782
 H                     2.05734129     1.32981120     0.02496974
 C                     1.09520984     0.79607173    -0.03872782
 H                     0.00000000    -1.59258557    -2.05035614
 C                     0.00000000    -1.20794408    -1.02589691
 H                     0.00000000     1.59258557    -2.05035614
 C                     0.00000000     1.20794408    -1.02589691
 H                     0.00000000    -1.45028854     1.97989592
 C                     0.00000000    -0.78106969     1.10677261
 H                     0.00000000     1.45028854     1.97989592
 C                     0.00000000     0.78106969     1.10677261
 H                    -2.05734129    -1.32981120     0.02496974
 C                    -1.09520984    -0.79607173    -0.03872782
 H                    -2.05734129     1.32981120     0.02496974
 C                    -1.09520984     0.79607173    -0.03872782
end

basis spherical
 H library cc-pVDZ
 C library cc-pVDZ
end

scf
 direct
end

tce
 mkccsd
 2emet 1
 freeze atomic
end

mrccdata
 root 1
 nref 2
 22222222222222222222222222220
 22222222222222222222222222202
end

task tce freq


I ran it on my personal 4-core computer and
get the following benchmarks

Symmetry of references

Ref.   1 sym:a   
Ref.   2 sym:a   
MR MkCCSD, version 1.0

Heff
=============================================
    0    1 -664.87322151    0.09099694
    0    2    0.09099694 -664.79730579

Eigenvalues (real and imaginary)
=============================================
 -664.933860013217    0.00000000
 -664.736667291187    0.00000000

Left eigenvectors
=============================================
    1   -0.83216055   -0.55453478
    2    0.55453478   -0.83216055

Right eigenvectors
=============================================
VR    1   -0.83216055   -0.55453478
VR    2    0.55453478   -0.83216055
Target root:    1

MkCC iter. #   1      -664.9338600132171      -307.3328942731508      -664.9338600132171
ddot R:  0.049763349351  1.692918082150
Iter cpu           236.1          315.6   1


I ran it on Kogence 128-core instance
https://kogence.com/app/jobs/files/list/-632%5ETransition_state_of_Cubane_and_azo-Cubane_t....
and have got
Symmetry of references

Ref.   1 sym:a   
Ref.   2 sym:a   
MR MkCCSD, version 1.0

Heff
=============================================
    0    1 -664.87322151    0.09099694
    0    2    0.09099694 -664.79730579

Eigenvalues (real and imaginary)
=============================================
 -664.933860013248    0.00000000
 -664.736667291216    0.00000000

Left eigenvectors
=============================================
    1   -0.83216055   -0.55453478
    2    0.55453478   -0.83216055

Right eigenvectors
=============================================
VR    1   -0.83216055   -0.55453478
VR    2    0.55453478   -0.83216055
Target root:    1

MkCC iter. #   1      -664.9338600132476      -307.3328942731813      -664.9338600132476
ydot R:  0.043047295224  1.692940929883
Iter cpu             3.7           64.3   1


128-core isn't faster 32 times, it faster only 5 times.

Why this happens?

Best Vladimir.