Error in Partial Hessian Vibrational Analysis

Questions
#1

When I run a PHVA of a large system, I see this error:
" You cannot request more PEs than atoms"

This does not go away whether I reduce the number of atoms for which I need a hessian or increase set_iter (which I think allows for more cpscf steps).

Any suggestions on how to get around this error? I see this reported as a bug in trac that is not yet resolved.

#2

Hello ssharada,

Could you post the input file? If it’s confidential, you may build a model system that can reproduce the error.

Thanks

#3

it’s ticket 2969, still unresolved

#4

Hi Shaama,
I ran you molecule, with a slightly modified $rem (only to make it run faster):

$rem
jobtype freq
max_scf_cycles 1000
method hf
basis general
ecp general
smx_gas_phase true
mem_total 110000
mem_static 8000
scf_convergence 5
thresh 12
PHESS      TRUE
xc_grid    1
N_SOL      8
cpscf_nseg 8 ! maybe has to be equal to N_SOL?
set_iter   100
$end

$basis
    Cu
    lanl2dz
****
    C
    6-31g
****
    N
    6-31g
****
    O
    6-31g
****
    H
    sto-3g
****
$end

$ecp
    Cu
    fit-lanl2dz
****
$end

$alist
1
2
3
4
5
6
7
8
$end

This version runs to completion on 8 processors. Key part of output:

 CPSCF will be done in 8 segments to save memory.

(This was set automatically but you could set with CPSCF_NSEG in $rem.) Note that I did have to increase SET_ITER; the segments took up to 36 iterations to converge the CPSCF equations.)

I think this is not so much a bug as a limitation of the current implementation: number of processors (PEs) cannot exceed number of atoms (even for full Hessian), and in partial Hessian the number of atoms is N_SOL.

Please try this with your real job and let us know how it turns out.

#5

The CPSCF iterations are running, very slow with 8 cores, but no issues so far. I didn’t need to set CPSCF_NSEG. Will update if I see any other errors. Thank you, John!

#6

I’ve updated the relevant bug ticket with this information, for what it’s worth.