Deleting extraneous files from destination: rsync

There were some reported non-functioning --delete flag when using rsync in syncronizing two filesystems/locations. This may occur due to failures or errors during rsync tries to sync zero size files. One simple work around for this is using --ignore-errors flag. Some examples for taking backup of user directory:

rsync -vaz -e ssh --delete --ignore-errors user@host:/home/user/ local_dir/
rsync -vaz --delete --ignore-errors /home/user/ /media/disk/backup_dir/

TCL Bad Code Error

Using tcl extension would be quite reasonable to write a flexable code. How ever if you use parse command set and TCL_OK as a return, be sure that type of your function is int, otherwise tcl complains with a strange run time error, saying bad code. So, be sure about the correct return type.

Traffic Utilization on router high CPU usage.

Long time ago, I was trying to address traffic utilization issues on border routers. This is the summary of my communication with nsp mailing list [Traffic Utilization Summary].

Simple syncronization via ssh with rsync.

One can syncronize two different locations by using rsync via ssh or without ssh.
Here are the steps:

1. get from the other location
rsync -avuzb dir/mydir/ .

2. put into other location
rsync -Cavuzb . dir/mydir/

If one of the location is reachable via ssh then one ca write

rsync -avz -e ssh remoteuser@remotehost:/remote/dir /this/dir/

Look at the man pages for more details. Actually -e flag is not needed.

CPU Timing in a C code

Examine this simple example :

#include < stdio.h >
#include < stdlib.h >
#include < time.h >
#include < math.h >

int main();

int main() {
  long int i,a;
  clock_t cputime,cputime1;
  double timing,timing0;
   cputime= clock();
    for(i=0;i<10000000;i++){
       a=pow(4,2);
       a=pow(4,2);
       a=pow(4,2);
       a=pow(4,2);
       a=pow(4,2);
      }

   cputime1= clock();
   timing0=((double) cputime1-cputime);
   timing=((double) cputime1-cputime) / CLOCKS_PER_SEC;
   printf("timing =%12.9f clock per sec=%d timing0=%12.9f\n",
          timing,CLOCKS_PER_SEC,timing0);
   exit(0);
}

Latex Poster: A working full example

You must use Latex to generate your posters, because it looks beautiful. Here is fully working and self contained example [latex_poster].

Simple scripts: Compressing Files & Cluster Queue Jobs Termination

If you would like to compress your data files or any type recursively you can use this simple perl script [datcompress].

Sometimes it is annoying to delete all your PBS jobs one by one, so simple perl script helps [deleteall].

How to benchmark communication cost in the beowulf (parallel system)

Quite long time ago, I've proposed one simple way of estimating
communication cost of an MPI program (or multiple-instruction)
appeared in the beowulf mailing list. Here is the outline of
the procedure.
[original post]

Definition Communication cost (Comm) is the ratio between the real
time used by all processors (processes actually if you use MPI)
and global real cpu time (GRU).

 Comm=GRU/GR = (GR-GU-GS)/GR 

Undefined symbols are as follows:

Comm= Communication cost
GR=global real time
LR=local worked real time 
LU=local user
LS=local system
GS=global system
GU=global user
n=# of procs
GU=n*LU
GS=n*LS
GR=n*LR 

In the actual MPI program this measure's implementation could be outlined
as follows

 BEGIN PROGRAM Myprogram
      begin distribution
       initial_timings=timings;
                ...do whatever is your distributed computing....
       end_timings=timings;
      end distribution
       if(myrank == 0) {compute communication cost}        
END Myprogram

BEGIN PROC timings
    for(n=0;n < numproc;numproc) {
       if(n==myrank) { measure timing of myrank and send to rank 0 }
     }
END PROC