From 9aad99e1432cef9cbc9e6b713b439c2bcf7a9df9 Mon Sep 17 00:00:00 2001
From: wolf <wolf@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Fri, 16 Apr 2004 20:49:34 +0000
Subject: [PATCH] Have a function that copies a sequential into a parallel
 vector, but only the local part.

git-svn-id: https://svn.dealii.org/trunk@9030 0785d39b-7218-0410-832d-ea1e28bc413d
---
 .../lac/include/lac/petsc_parallel_vector.h   | 37 +++++++++++++++++++
 deal.II/lac/source/petsc_parallel_vector.cc   | 35 +++++++++++++++++-
 2 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/deal.II/lac/include/lac/petsc_parallel_vector.h b/deal.II/lac/include/lac/petsc_parallel_vector.h
index 2c3f9bd774..6eb511a7d0 100644
--- a/deal.II/lac/include/lac/petsc_parallel_vector.h
+++ b/deal.II/lac/include/lac/petsc_parallel_vector.h
@@ -130,6 +130,43 @@ namespace PETScWrappers
                                           */
         Vector & operator = (const Vector &v);
 
+                                         /**
+					  * Copy the given sequential
+					  * (non-distributed) vector
+					  * into the present parallel
+					  * vector. It is assumed that
+					  * they have the same size,
+					  * and this operation does
+					  * not change the
+					  * partitioning of the
+					  * parallel vector by which
+					  * its elements are
+					  * distributed across several
+					  * MPI processes. What this
+					  * operation therefore does
+					  * is to copy that chunk of
+					  * the given vector @p v that
+					  * corresponds to elements of
+					  * the target vector that are
+					  * stored locally, and copies
+					  * them. Elements that are
+					  * not stored locally are not
+					  * touched.
+					  *
+					  * This being a parallel
+					  * vector, you must make sure
+					  * that @em all processes
+					  * call this function at the
+					  * same time. It is not
+					  * possible to change the
+					  * local part of a parallel
+					  * vector on only one
+					  * process, independent of
+					  * what other processes do,
+					  * with this function.
+					  */
+	Vector & operator = (const PETScWrappers::Vector &v);
+
                                          /**
                                           * Set all components of the vector to
                                           * the given number @p{s}. Simply pass
diff --git a/deal.II/lac/source/petsc_parallel_vector.cc b/deal.II/lac/source/petsc_parallel_vector.cc
index 733190a246..35491c5beb 100644
--- a/deal.II/lac/source/petsc_parallel_vector.cc
+++ b/deal.II/lac/source/petsc_parallel_vector.cc
@@ -13,8 +13,10 @@
 
 
 #include <lac/petsc_parallel_vector.h>
+#include <lac/petsc_vector.h>
 
 #include <cmath>
+#include <algorithm>
 
 #ifdef DEAL_II_USE_PETSC
 
@@ -105,7 +107,38 @@ namespace PETScWrappers
       
       reinit (v.size(), v.local_size(), fast);
     }
-  
+
+
+
+    Vector &
+    Vector::operator = (const PETScWrappers::Vector &v)
+    {
+      int ierr;
+
+                            // get a pointer to the local memory of this vector
+      PetscScalar *dest_array;
+      ierr = VecGetArray (vector, &dest_array);
+      AssertThrow (ierr == 0, ExcPETScError(ierr));
+
+                            // then also a pointer to the source vector
+      PetscScalar *src_array;
+      ierr = VecGetArray (static_cast<const Vec &>(v), &src_array);
+      AssertThrow (ierr == 0, ExcPETScError(ierr));
+
+      // then copy:
+      const std::pair<unsigned int, unsigned int> local_elements = local_range ();
+      std::copy (src_array + local_elements.first, src_array + local_elements.second,
+		 dest_array);
+
+      // finally restore the arrays
+      ierr = VecRestoreArray (vector, &dest_array);
+      AssertThrow (ierr == 0, ExcPETScError(ierr));
+
+      ierr = VecRestoreArray (static_cast<const Vec &>(v), &src_array);
+      AssertThrow (ierr == 0, ExcPETScError(ierr));
+
+      return *this;
+    }
 
 
     void
-- 
2.39.5