[petsc-users] PetscOptionsGetRealArray command line format

[Jed Brown]

Xiangdong <epscodes at gmail.com> writes:

> I have a simple script (see below) by just
> calling PetscOptionsGetRealArray. I run the program like this: mpirun -np
> 1 runarraytest -myarray 1,2,3,4,5. However, the output is always "the
> length of input myarray is 0".
>
> Can you produce the correct result? Thank you.

$ valgrind ./a -myarray 1,2,3
==8778== Memcheck, a memory error detector
==8778== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==8778== Using Valgrind-3.9.0 and LibVEX; rerun with -h for copyright info
==8778== Command: ./a -myarray 1,2,3
==8778== 
==8778== Conditional jump or move depends on uninitialised value(s)
==8778==    at 0x4EBBB6F: PetscOptionsGetRealArray (options.c:1863)
==8778==    by 0x400861: main (a.c:11)
==8778== 
the length of input myarray is 0 
[...]

Hmm,

options.c:1863   while (n < *nmax) {


Yup, you definitely have to initialize nmax before calling the function.

> Below is the script I use:
>
>
> #include <petsc.h>
>
> int main(int argc, char **argv)
> {
>   PetscInitialize(&argc, &argv, PETSC_NULL, PETSC_NULL);
>
>   double myarray[10];
>   int nmax;
>   PetscBool flg;
>

Add nmax = 10;

>   PetscOptionsGetRealArray(NULL,"-myarray",myarray,&nmax,&flg);
>
>   printf("the length of input myarray is %d \n",nmax);
>
>   int i;
>   for(i=0;i<nmax;++i)
>     {
>       printf(" %g\n",myarray[i]);
>     }
>
>   PetscFinalize();
>   return 0;
> }
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