[Pw_forum] density files

[Silviu Zilberman]

Dear All,

I have noticed that now the charge density files are saved by default in 
CP calculations and this is not affected by the disk_io input parameter. 
Generally this is not a problem, but it can be in certain circumstances, 
like restricted disk space/quota.

I have been running calculations on Lemieux which is an alpha cluster 
super computer in Pittsburgh. For some reason that is still mysterious 
to me, writing these density files on the scratch space took very long 
time, ~30 (!) minutes for a 68MB file. My calculation is spin-polarized 
and thus I have 3 such density files, and in addition I want to use the 
string method, which will multiply the number of these files by N-2, 
where N is the number of images. The mystery is further enhanced by the 
fact that (a) the wavefinction files (~23 MB) are dumped rather quickly 
(less than 30 sec) and (b) if I repeat the calculation on our 
pc-cluster, writing everything takes ~37 sec which is reasonable.

I would appreciate your comments on:
(a) What is the reasoning behind making the cp code dump density files 
by default?
(b) Did anyone experience such anomalous I/O rates on Lemieux or any 
other cluster.

Thanks, Silviu.