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// $Id: block_indices.h 30040 2013-07-18 17:06:48Z maier $
//
// Copyright (C) 2000 - 2013 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library is free software; you can use it, redistribute
// it, and/or modify it under the terms of the GNU Lesser General
// Public License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// The full text of the license can be found in the file LICENSE at
// the top level of the deal.II distribution.
//
// ---------------------------------------------------------------------
#ifndef __deal2__block_indices_h
#define __deal2__block_indices_h
#include <deal.II/base/config.h>
#include <deal.II/base/subscriptor.h>
#include <deal.II/base/exceptions.h>
#include <deal.II/base/logstream.h>
#include <cstddef>
#include <vector>
DEAL_II_NAMESPACE_OPEN
/**
* @brief Auxiliary class aiding in the handling of block structures like in
* BlockVector or FESystem.
*
* The information obtained from this class falls into two
* groups. First, it is possible to obtain the number of blocks,
* namely size(), the block_size() for each block and the total_size()
* of the object described by the block indices, namely the length of
* the whole index set. These functions do not make any assumption on
* the ordering of the index set.
*
* If on the other hand the index set is ordered "by blocks", such
* that each block forms a consecutive set of indices, this
* class that manages the conversion of global indices into a block vector or
* matrix to the local indices within this block. This is required, for
* example, when you address a global element in a block vector and want to
* know which element within which block this is. It is also useful if a
* matrix is composed of several blocks, where you have to translate global
* row and column indices to local ones.
*
* @ingroup data
* @see @ref GlossBlockLA "Block (linear algebra)"
* @author Wolfgang Bangerth, Guido Kanschat, 2000, 2007, 2011
*/
class BlockIndices : public Subscriptor
{
public:
/**
* Declare the type for container size.
*/
typedef types::global_dof_index size_type;
/**
* Default
* constructor. Initialize for
* zero blocks.
*/
BlockIndices ();
/**
* Constructor. Initialize the
* number of entries in each
* block @p i as <tt>n[i]</tt>. The
* number of blocks will be the
* size of the vector
*/
BlockIndices (const std::vector<size_type> &n);
/**
* Specialized constructor for a
* structure with blocks of equal size.
*/
explicit BlockIndices(const unsigned int n_blocks, const size_type block_size = 0);
/**
* Reinitialize the number of
* blocks and assign each block
* the same number of elements.
*/
void reinit (const unsigned int n_blocks,
const size_type n_elements_per_block);
/**
* Reinitialize the number of
* indices within each block from
* the given argument. The number
* of blocks will be adjusted to
* the size of @p n and the size
* of block @p i is set to
* <tt>n[i]</tt>.
*/
void reinit (const std::vector<size_type> &n);
/**
* Add another block of given
* size to the end of the block
* structure.
*/
void push_back(const size_type size);
/**
* @name Size information
*/
//@{
/**
* Number of blocks in index field.
*/
unsigned int size () const;
/**
* Return the total number of
* indices accumulated over all
* blocks, that is, the dimension
* of the vector space of the
* block vector.
*/
size_type total_size () const;
/**
* The size of the @p ith block.
*/
size_type block_size (const unsigned int i) const;
//@}
/**
* @name Index conversion
*
* Functions in this group
* assume an object, which
* was created after sorting by
* block, such that each block
* forms a set of consecutive
* indices in the object.
* If applied to other objects,
* the numbers obtained from
* these functions are meaningless.
*/
//@{
/**
* Return the block and the
* index within that block
* for the global index @p i. The
* first element of the pair is
* the block, the second the
* index within it.
*/
std::pair<unsigned int,size_type>
global_to_local (const size_type i) const;
/**
* Return the global index of
* @p index in block @p block.
*/
size_type local_to_global (const unsigned int block,
const size_type index) const;
/**
* The start index of the ith block.
*/
size_type block_start (const unsigned int i) const;
//@}
/**
* Copy operator.
*/
BlockIndices &operator = (const BlockIndices &b);
/**
* Compare whether two objects
* are the same, i.e. whether the
* number of blocks and the sizes
* of all blocks are equal.
*/
bool operator == (const BlockIndices &b) const;
/**
* Swap the contents of these two
* objects.
*/
void swap (BlockIndices &b);
/**
* Determine an estimate for the
* memory consumption (in bytes)
* of this object.
*/
std::size_t memory_consumption () const;
private:
/**
* Number of blocks. While this
* value could be obtained
* through
* <tt>start_indices.size()-1</tt>,
* we cache this value for faster
* access.
*/
unsigned int n_blocks;
/**
* Global starting index of each
* vector. The last and redundant
* value is the total number of
* entries.
*/
std::vector<size_type> start_indices;
};
/**
* Operator for logging BlockIndices. Writes the number of blocks, the
* size of each block and the total size of the index field.
*
* @ref BlockIndices
* @author Guido Kanschat
* @date 2011
*/
inline
LogStream &
operator << (LogStream &s, const BlockIndices &bi)
{
const unsigned int n = bi.size();
s << n << ":[";
// Write first size without leading space
if (n>0)
s << bi.block_size(0);
// Write all other sizes
for (unsigned int i=1; i<n; ++i)
s << ' ' << bi.block_size(i);
s << "]->" << bi.total_size();
return s;
}
template <typename MatrixType> class BlockMatrixBase;
template <typename SparsityType> class BlockSparsityPatternBase;
template <typename number> class BlockSparseMatrixEZ;
/**
* A class that can be used to determine whether a given type is a block
* matrix type or not. For example,
* @code
* IsBlockMatrix<SparseMatrix<double> >::value
* @endcode
* has the value false, whereas
* @code
* IsBlockMatrix<BlockSparseMatrix<double> >::value
* @endcode
* is true. This is sometimes useful in template contexts where we may
* want to do things differently depending on whether a template type
* denotes a regular or a block matrix type.
*
* @see @ref GlossBlockLA "Block (linear algebra)"
* @author Wolfgang Bangerth, 2009
*/
template <typename MatrixType>
struct IsBlockMatrix
{
private:
struct yes_type
{
char c[1];
};
struct no_type
{
char c[2];
};
/**
* Overload returning true if the class
* is derived from BlockMatrixBase,
* which is what block matrices do
* (with the exception of
* BlockSparseMatrixEZ).
*/
template <typename T>
static yes_type check_for_block_matrix (const BlockMatrixBase<T> *);
/**
* Overload returning true if the class
* is derived from
* BlockSparsityPatternBase, which is
* what block sparsity patterns do.
*/
template <typename T>
static yes_type check_for_block_matrix (const BlockSparsityPatternBase<T> *);
/**
* Overload for BlockSparseMatrixEZ,
* which is the only block matrix not
* derived from BlockMatrixBase at the
* time of writing this class.
*/
template <typename T>
static yes_type check_for_block_matrix (const BlockSparseMatrixEZ<T> *);
/**
* Catch all for all other potential
* matrix types that are not block
* matrices.
*/
static no_type check_for_block_matrix (...);
public:
/**
* A statically computable value that
* indicates whether the template
* argument to this class is a block
* matrix (in fact whether the type is
* derived from BlockMatrixBase<T>).
*/
static const bool value = (sizeof(check_for_block_matrix
((MatrixType *)0))
==
sizeof(yes_type));
};
// instantiation of the static member
template <typename MatrixType>
const bool IsBlockMatrix<MatrixType>::value;
/* ---------------------- template and inline functions ------------------- */
inline
void
BlockIndices::reinit (const unsigned int nb,
const size_type block_size)
{
n_blocks = nb;
start_indices.resize(n_blocks+1);
for (size_type i=0; i<=n_blocks; ++i)
start_indices[i] = i * block_size;
}
inline
void
BlockIndices::reinit (const std::vector<size_type> &n)
{
if (start_indices.size() != n.size()+1)
{
n_blocks = static_cast<unsigned int>(n.size());
start_indices.resize(n_blocks+1);
}
start_indices[0] = 0;
for (size_type i=1; i<=n_blocks; ++i)
start_indices[i] = start_indices[i-1] + n[i-1];
}
inline
BlockIndices::BlockIndices ()
:
n_blocks(0),
start_indices(1, 0)
{}
inline
BlockIndices::BlockIndices (
const unsigned int n_blocks,
const size_type block_size)
:
n_blocks(n_blocks),
start_indices(n_blocks+1)
{
for (size_type i=0; i<=n_blocks; ++i)
start_indices[i] = i * block_size;
}
inline
BlockIndices::BlockIndices (const std::vector<size_type> &n)
:
n_blocks(static_cast<unsigned int>(n.size())),
start_indices(n.size()+1)
{
reinit (n);
}
inline
void
BlockIndices::push_back(const size_type sz)
{
start_indices.push_back(start_indices[n_blocks]+sz);
++n_blocks;
AssertDimension(start_indices.size(), n_blocks+1);
}
inline
std::pair<unsigned int,BlockIndices::size_type>
BlockIndices::global_to_local (const size_type i) const
{
Assert (i<total_size(), ExcIndexRangeType<size_type>(i, 0, total_size()));
Assert (n_blocks > 0, ExcLowerRangeType<size_type>(i, size_type(1)));
unsigned int block = n_blocks-1;
while (i < start_indices[block])
--block;
return std::pair<size_type,size_type>(block,
i-start_indices[block]);
}
inline
BlockIndices::size_type
BlockIndices::local_to_global (const unsigned int block,
const size_type index) const
{
Assert (block < n_blocks, ExcIndexRange(block, 0, n_blocks));
Assert (index < start_indices[block+1]-start_indices[block],
ExcIndexRangeType<size_type> (index, 0, start_indices[block+1]-start_indices[block]));
return start_indices[block]+index;
}
inline
unsigned int
BlockIndices::size () const
{
return n_blocks;
}
inline
BlockIndices::size_type
BlockIndices::total_size () const
{
if (n_blocks == 0) return 0;
return start_indices[n_blocks];
}
inline
BlockIndices::size_type
BlockIndices::block_size (const unsigned int block) const
{
Assert (block < n_blocks, ExcIndexRange(block, 0, n_blocks));
return start_indices[block+1]-start_indices[block];
}
inline
BlockIndices::size_type
BlockIndices::block_start (const unsigned int block) const
{
Assert (block < n_blocks, ExcIndexRange(block, 0, n_blocks));
return start_indices[block];
}
inline
BlockIndices &
BlockIndices::operator = (const BlockIndices &b)
{
start_indices = b.start_indices;
n_blocks = b.n_blocks;
return *this;
}
inline
bool
BlockIndices::operator == (const BlockIndices &b) const
{
if (n_blocks != b.n_blocks)
return false;
for (size_type i=0; i<=n_blocks; ++i)
if (start_indices[i] != b.start_indices[i])
return false;
return true;
}
inline
void
BlockIndices::swap (BlockIndices &b)
{
Assert (n_blocks == b.n_blocks,
ExcDimensionMismatch(n_blocks, b.n_blocks));
for (size_type i=0; i<=n_blocks; ++i)
std::swap (start_indices[i], b.start_indices[i]);
}
inline
std::size_t
BlockIndices::memory_consumption () const
{
return (sizeof(*this) +
start_indices.size() * sizeof(start_indices[0]));
}
/* ----------------- global functions ---------------------------- */
/**
* Global function @p swap which overloads the default implementation
* of the C++ standard library which uses a temporary object. The
* function simply exchanges the data of the two objects.
*
* @relates BlockIndices
* @author Wolfgang Bangerth, 2000
*/
inline
void swap (BlockIndices &u, BlockIndices &v)
{
u.swap (v);
}
DEAL_II_NAMESPACE_CLOSE
#endif
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