PETSc Problem with fgets

[Sh.M]

Hi,

I apologize in advance if I am confusing you or down right saying something
that is wrong.

When I initially checked you code, it looks like CPU O is opening the
file... but the rest of the CPUs try to read it aswell even though they
havent opened(dont have a correct file pointer to the file) it yet... This
would cause a segmentation fault. fgets is using the fd variable, wich in
case of anything but CPU 0 are pointing to some garbage and not the file
itself.

With best regards, Shaman Mahmoudi

----- Original Message ----- 
From: "Joshua Adelman" <jadelman at ocf.berkeley.edu>
To: <petsc-users at mcs.anl.gov>
Sent: Friday, May 12, 2006 12:54 AM
Subject: PETSc Problem with fgets


> I am trying to read some parameters into my PETSc simulation using
> fgets, and am getting a strange error. It appears that fgets and
> sscanf are working since the proper values are read into the
> simulation, but it throws an error anyways. This problem only arises
> when I am using the parallel version of the code (i.e. setting -n in
> mpiexec to a value greater than 1). Basically if I comment everything
> out and then start uncommenting one line at a time, the error appears
> once I've uncommented the line with fgets. One strange thing to note
> is that the error happens after the program has already finished
> executing the function where the problem is. Here's a snippet of the
> code that seems to be causing the problem:
>
> PetscErrorCode DataReadParams(SimData *sdata) {
> int rank, size;
> PetscErrorCode ierr;
> int i;
> FILE *fd;
> char        str[256];
> char line[100];
> int max = 100;
>
> PetscFunctionBegin;
>
> ierr = MPI_Comm_size(PETSC_COMM_WORLD,&size); CHKERRQ(ierr);
> ierr = MPI_Comm_rank(PETSC_COMM_WORLD,&rank); CHKERRQ(ierr);
>
>
> /* Read data from files */
> sprintf(str,"%s%s",sdata->simname,".param");
> ierr = PetscFOpen(PETSC_COMM_WORLD,str,"r",&fd); CHKERRQ(ierr);
> if (!rank && !fd) {
>     SETERRQ1(PETSC_ERR_FILE_OPEN,"Cannot open %s\n",str);
> }
> // PetscPrintf(PETSC_COMM_WORLD,"Opening file %s\n",str);
> fgets(line,max,fd);
>     sscanf(line,"%d",&sdata->NP);
>
> The error that is kicked out is:
>
>
> [1]PETSC ERROR: Caught signal number 10 BUS: Bus Error, possibly
> illegal memory access
> [1]PETSC ERROR: Try option -start_in_debugger or -
> on_error_attach_debugger
> [1]PETSC ERROR: or try http://valgrind.org on linux to find memory
> corruption errors
> [1]PETSC ERROR: likely location of problem given in stack below
> [1]PETSC ERROR: --------------- Stack Frames ---------------
> [1]PETSC ERROR: Note: The EXACT line numbers in the stack are not
> available,
> [1]PETSC ERROR:       INSTEAD the line number of the start of the
> function
> [1]PETSC ERROR:       is given.
> [1]PETSC ERROR: [1] DataReadParams line 23 datareadparams.c
> [1]PETSC ERROR: [1] SimInit line 19 siminit.c
> [1]PETSC ERROR: --------------------------------------------
> [1]PETSC ERROR: User provided function() line 0 in unknown directory
> unknown file
> [1]PETSC ERROR: Signal received!
> [1]PETSC ERROR:  !
>
>
> Any insight would be most appreciated.
>
> Josh
>
> ------------------------------------------------------------------------ 
> ------------------------------
> Joshua L. Adelman
> Biophysics Graduate Group              Lab: 510.643.2159
> 218 Wellman Hall                                Fax: 510.642.7428
> University of California, Berkeley     http://www.ocf.berkeley.edu/
> ~jadelman
> Berkeley, CA 94720 USA                   jadelman at ocf.berkeley.edu
> ------------------------------------------------------------------------ 
> ------------------------------
>
>
>