bool output_details;
};
-
-
/**
* Empty Constructor. You need to call
* initialize() before using this
*/
AdditionalData additional_data;
};
+
+
+
+/**
+ * A class that implements the interface to use the ParaSails sparse
+ * approximate inverse preconditioner from the HYPRE suite. Note that
+ * PETSc has to be configured with HYPRE (e.g. with --download-hypre=1).
+ *
+ * ParaSails uses least-squares minimization to compute a sparse
+ * approximate inverse. The sparsity pattern used is the pattern
+ * of a power of a sparsified matrix. ParaSails also uses a post-filtering
+ * technique to reduce the cost of applying the preconditioner.
+ *
+ * ParaSails solves symmetric positive definite (SPD) problems
+ * using a factorized SPD preconditioner and can also solve
+ * general (nonsymmetric and/or indefinite) problems with a
+ * nonfactorized preconditioner. The problem type has to be
+ * set in @p AdditionalData.
+ *
+ * The preconditioner does support parallel distributed computations.
+ *
+ * @ingroup PETScWrappers
+ * @author Martin Steigemann, 2012
+ */
+ class PreconditionParaSails : public PreconditionerBase
+ {
+ public:
+ /**
+ * Standardized data struct to
+ * pipe additional flags to the
+ * preconditioner.
+ */
+ struct AdditionalData
+ {
+ /**
+ * Constructor.
+ */
+ AdditionalData (
+ const unsigned int symmetric = 1,
+ const unsigned int n_levels = 1,
+ const double threshold = 0.1,
+ const double filter = 0.05,
+ const bool output_details = false
+ );
+
+ /**
+ * This parameter specifies the
+ * type of problem to solve:
+ * <ul>
+ * <li> @p 0: nonsymmetric and/or indefinite problem, and nonsymmetric preconditioner
+ * <li> @p 1: SPD problem, and SPD (factored) preconditioner
+ * <li> @p 2: nonsymmetric, definite problem, and SPD (factored) preconditioner
+ * </ul>
+ * Default is <tt>symmetric = 1</tt>.
+ */
+ unsigned int symmetric;
+
+ /**
+ * Patterns of powers of sparsified
+ * matrices can be approximate the
+ * pattern of large entries in the
+ * inverse of a matrix. Powers of a
+ *
+ * The sparsity pattern used for the
+ * apprximate inverse is the pattern
+ * of a power <tt>B^m</tt> where <tt>B</tt>
+ * has been sparsified from the given
+ * matrix <tt>A</tt>, <tt>n_level</tt>
+ * is equal to <tt>m+1</tt>. Default
+ * value is <tt>n_levels = 1</tt>.
+ */
+ unsigned int n_levels;
+
+ /**
+ * Sparsification is performed by
+ * dropping nonzeros which are smaller
+ * than <tt>thresh</tt> in magnitude.
+ * Lower values of <tt>thresh</tt>
+ * lead to more accurate, but also more
+ * expensive preconditioners. Default
+ * value is <tt>thresh = 0.1</tt>. Setting
+ * <tt>thresh < 0</tt> a threshold
+ * is selected automatically, such that
+ * <tt>-thresh</tt> represents the
+ * fraction of nonzero elements that are
+ * dropped. For example, if <tt>thresh = -0.9</tt>,
+ * then <tt>B</tt> will contain about
+ * ten percent of the nonzeros of the
+ * given matrix <tt>A</tt>.
+ */
+ double threshold;
+
+ /**
+ * Filtering is a post-processing procedure,
+ * <tt>filter</tt> represents a fraction
+ * of nonzero elements that are dropped
+ * after creating the approximate inverse
+ * sparsity pattern. Default value is
+ * <tt>filter = 0.05</tt>. Setting <tt>filter < 0</tt>
+ * a value is selected automatically, such
+ * that <tt>-filter</tt> represents the
+ * fraction of nonzero elements that are
+ * dropped. For example, if <tt>thresh = -0.9</tt>,
+ * then about 90 percent of the entries
+ * in the computed approximate inverse are
+ * dropped.
+ */
+ double filter;
+
+ /**
+ * Setting this flag to true
+ * produces output from HYPRE,
+ * when the preconditioner
+ * is constructed.
+ */
+ bool output_details;
+ };
+
+
+
+ /**
+ * Empty Constructor. You need to call
+ * initialize() before using this
+ * object.
+ */
+ PreconditionParaSails ();
+
+ /**
+ * Constructor. Take the matrix which
+ * is used to form the preconditioner,
+ * and additional flags if there are
+ * any.
+ */
+ PreconditionParaSails (const MatrixBase &matrix,
+ const AdditionalData &additional_data = AdditionalData());
+
+ /**
+ * Initializes the preconditioner
+ * object and calculate all data that
+ * is necessary for applying it in a
+ * solver. This function is
+ * automatically called when calling
+ * the constructor with the same
+ * arguments and is only used if you
+ * create the preconditioner without
+ * arguments.
+ */
+ void initialize (const MatrixBase &matrix,
+ const AdditionalData &additional_data = AdditionalData());
+
+ private:
+ /**
+ * Store a copy of the flags for this
+ * particular preconditioner.
+ */
+ AdditionalData additional_data;
+ };
+
+
+
+/**
+ * A class that implements a non-preconditioned method.
+ *
+ * @ingroup PETScWrappers
+ * @author Martin Steigemann, 2012
+ */
+ class PreconditionNone : public PreconditionerBase
+ {
+ public:
+ /**
+ * Standardized data struct to
+ * pipe additional flags to the
+ * preconditioner.
+ */
+ struct AdditionalData
+ {};
+
+ /**
+ * Empty Constructor. You need to call
+ * initialize() before using this
+ * object.
+ */
+ PreconditionNone ();
+
+ /**
+ * Constructor. Take the matrix which
+ * is used to form the preconditioner,
+ * and additional flags if there are
+ * any. The matrix is completely
+ * ignored in computations.
+ */
+ PreconditionNone (const MatrixBase &matrix,
+ const AdditionalData &additional_data = AdditionalData());
+
+ /**
+ * Initializes the preconditioner
+ * object and calculate all data that
+ * is necessary for applying it in a
+ * solver. This function is
+ * automatically called when calling
+ * the constructor with the same
+ * arguments and is only used if you
+ * create the preconditioner without
+ * arguments. The matrix is completely
+ * ignored in computations.
+ */
+ void initialize (const MatrixBase &matrix,
+ const AdditionalData &additional_data = AdditionalData());
+
+ private:
+ /**
+ * Store a copy of the flags for this
+ * particular preconditioner.
+ */
+ AdditionalData additional_data;
+ };
}
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