Hi Klaus,
there are several options, e.g.:
*
http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Vec/VecCreateSeqWithArray.html
(sequential)
*
http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Vec/VecSetValues.html
(use with multiple MPI ranks if you cannot easily determine the local parts)
*
http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Vec/VecGetArray.html
(get a pointer to the data and assign values yourself)
Best regards,
Karli
On 09/28/2017 02:43 PM, Klaus Burkart wrote:
Hello,
I want to solve a physics problem with support of petsc i.e. solve the
linear system using petsc. So far I have been using another linear
algebra library. I am using c++. Now I am struggling to load the rhs
vector/array from the physics application to petsc and copying the
result x back to the physics application. I found information about how
to load data from binaries or from files but both is not the case here.
The computation will take place on a multi core CPU using MPI.
This is how far I am and includes my questions:
...
#include <petscvec.h>
// vector x, rhs size n; "matrix" is the matrix from the physics application
PetscMPIInt n = matrix.diag().size();
Vec rhs; // Question 1: How to set the value type to double?
VecSetSizes(rhs, n, PETSC_DECIDE); // Question 2: What is "global size"?
Vec x;
VecSetSizes(x, n, PETSC_DECIDE);
// Question 3:
// How to load petsc rhs vector with data from vector (= pointer array)
named rhs_source?
// Current load/copy syntax is: fast_copy(rhs_source.begin(),
rhs_source.end(), rhs.begin());
// Question 4:
// How to export petsc result vector x i.e. load the result x into array
named x_result?
// Current load/copy syntax is: fast_copy(x.begin(), x.end(),
x_result.begin());
// destroy petsc vectors
VecDestroy(&rhs);
VecDestroy(&x);
PetscFinalize();
// What's the best way to copy rhs to petsc and to copy the result x
back to the physics application?
