Subject: problem with g94 casscf77 under linux

From: BRION Jean <[email-masked]>
Date: Wed, 8 Jul 98 16:39:35 WETDST

Hello,

We have installed the Gaussian 94 package on a Linux machine
and we meet now one problem when trying a CASSCF(7,7) (generating
784 configurations)...
The problem is in link 510, when the program begins "Generating Lanczos Guess".
At this moment, we establish that the running does not create any output more...
(even with a long calculation time about 3000 minutes !). 

-We have a PII 400 machine, with 256Mo of memory and a 9Go hard disk.

-Gaussian version is D.4

-Linux version is S.u.S.e 1998

-the memory used for this calculation was 8MW

-The previous CASSCF(5,5) has worked very well in 5 minutes for 75
generated CONFIGURATIONS.

-When adding the FULLDIAG keyword in the CASSCF options list, the calculation
 works !  (but takes a long time)

- on a HP755 machine:
*
The same CASSCF(5,5) calculations takes about 10 minutes 
*
The same CASSCF(7,7) works very well, and takes about 12 minutes

We have tried another thing to try to solve
our problem: i.e add the -malign-double in the
compilator options.

=> Although other jobs (than the casscf(7,7) one)
run faster, our problem on the CASSCF(7,7)
remains the same (that means this job never stops
without output and without  error).

Has someone already met this difficulty ? Is this
a gaussian environement problem or a machine configuration problem ?

We have also tried to drop the -O2 option in the source's compilation 
with gcc. We have no idea any more at this time ...            

    Thank you in advance for your help.

		  E. Henon