Subject: ccl: iend, mxcore summary

From: Martijn Zwijnenburg <M.A.Zwijnenburg$at$tnw.tudelft.nl>
Date: Fri, 06 Jun 2003 19:37:39 +0200

Hi,

Thanx, to all those numerous people who responded to my question 
about what iend and mxcore are in G98 an why a job would fail if iend 
would be smaller then mxcore. Below I included the answer of Doug Fox 
(from Gaussian) which summarizes almost everything.

Thanx,

Martijn

Answer:
Gaussian 98 works with a fixed memory allocation which is set
in the input.  The default is 6MW (48MB) but you simply need to
add a line at the top of the input of the form

%mem=8MW

to increase this.

This is related to the error message as follows, iend is the amount 
of memory that Gaussian needs at this step.  MxCore is the amount of 
the total memory left at this point.  So when you get this message 
you need to increase the %mem value overall by the difference between 
these two. 

Looking at the fragment below you have the default memory as noted by

>  Leave Link  301 at Thu Jun  5 14:59:36 2003, MaxMem=    6291456 
cpu: 

and then some of it has been previously allocated at the time this 
failed,

>  ShPair-CalcS2-2 allocation failure:  iend,mxcore=   4107035   
4060616

and only 4MW are left.  The calculation was only a little short, 
needing
4107035 - 4060616 = 46419 words but generally you will do better to
allocate some excess.  So

%mem=7mw

would be plenty.

You can increase the default if you have more memory available by
putting a line in the /opt/g98/g98Default.Route file,

-M- 12MW

to request 96MB.  Just doing more memory will not always make it 
faster so don't allocate all of the available memory.  For a 512MB 
machine making the default 256MB is reasonable.  You can increase it 
for individual jobs if needed, as noted above.

Original question:
> 
> Hi,
> 
> We're trying to find the limitations of one of our machines (for 
> getting the specs for our new machines) and have noticed that some 
jobs
> crash upon increasing the basis-set with the following error 
message:
> 
> here are  1488 symmetry adapted basis functions of A   symmetry.
>  Crude estimate of integral set expansion from redundant 
> integrals=1.000.
>  Integral buffers will be    262144 words long.
>  Raffenetti 2 integral format.
>  Two-electron integral symmetry is turned on.
>   1488 basis functions     3232 primitive gaussians
>    432 alpha electrons      432 beta electrons
>        nuclear repulsion energy     32002.1321856990 Hartrees.
>       0.1
>  (Enter /opt/g98/g98/l302.exe)
>  One-electron integrals computed using PRISM.
>  Error termination via Lnk1e in /opt/g98/g98/l302.exe.
> 
> Can somebody explain what's happening here? and what are iend and 
> mxcore precisely? 
> 
> Thanx in advance
> 
> Cheers,
> 
> Martijn-------------------------------------------------------------
------------
Martijn Zwijnenburg
Lab. of Applied Organic Chemistry and Catalysis
Delft University of Technology
Julianalaan 136
2628 BL Delft
The Netherlands
Tel: 0031-(0)152782691
Fax: 0031-(0)152784700
e-mail: M.A.Zwijnenburg$at$tnw.tudelft.nl
web page: http://come.to/tock