From f33d54c29094910bd5b24c2be7109ed598ab2438 Mon Sep 17 00:00:00 2001
From: Wenqing Wang <wenqing.wang@ufz.de>
Date: Thu, 22 Mar 2018 10:01:36 +0100
Subject: [PATCH] [PETSc] Added a more detailed description of PETScMatrix::add
---
MathLib/LinAlg/PETSc/PETScMatrix.h | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/MathLib/LinAlg/PETSc/PETScMatrix.h b/MathLib/LinAlg/PETSc/PETScMatrix.h
index bca4e150691..2b29072f6a0 100644
--- a/MathLib/LinAlg/PETSc/PETScMatrix.h
+++ b/MathLib/LinAlg/PETSc/PETScMatrix.h
@@ -127,11 +127,30 @@ public:
MatSetValue(_A, i, j, value, ADD_VALUES);
}
- /// Add sub-matrix at positions given by \c indices.
+ /*!
+ \brief Add sub-matrix at positions given by global \c indices, in which
+ negative index indicates ghost entry.
+
+ In order to use MatZeroRows to apply Dirichlet boundary condition,
+ entries in the rows with the negative global indices are skipped to added
+ to the global matrix, meanwhile entries in the columns with the negative
+ global indices are added the global matrix. By using MatZeroRows to apply
+ Dirichlet boundary condition, the off diagonal entries in ghost rows of
+ the global matrix are set to zero, while the off diagonal entries in
+ ghost rows of the global matrix are assembled and kept for linear solver.
+
+ For the setting of Dirichlet boundary condition
+ in PETSc, please refer to
+ <a href="http://www.mcs.anl.gov/petsc/documentation/faq.html#redistribute">PETSc:Documentation:FAQ</a>
+ */
template <class T_DENSE_MATRIX>
void add(RowColumnIndices<PetscInt> const& indices,
const T_DENSE_MATRIX& sub_matrix)
{
+ // Set global column indices to positive to allow all entries of columns
+ // to be added to the global matrix. For the ghost columns, only the
+ // off diagonal entries are added due to the negative indices of the
+ // corresponding rows.
std::vector<PetscInt> cols;
cols.reserve(indices.columns.size());
for (auto col : indices.columns)
--
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