85 lines
3.1 KiB
C
85 lines
3.1 KiB
C
/*BHEADER**********************************************************************
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* Copyright (c) 2006 The Regents of the University of California.
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* Produced at the Lawrence Livermore National Laboratory.
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* Written by the HYPRE team. UCRL-CODE-222953.
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* All rights reserved.
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*
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* This file is part of HYPRE (see http://www.llnl.gov/CASC/hypre/).
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* Please see the COPYRIGHT_and_LICENSE file for the copyright notice,
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* disclaimer, contact information and the GNU Lesser General Public License.
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*
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* HYPRE is free software; you can redistribute it and/or modify it under the
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* terms of the GNU General Public License (as published by the Free Software
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* Foundation) version 2.1 dated February 1999.
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*
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* HYPRE is distributed in the hope that it will be useful, but WITHOUT ANY
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* WARRANTY; without even the IMPLIED WARRANTY OF MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the terms and conditions of the GNU General
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* Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* $Revision$
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***********************************************************************EHEADER*/
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#include "hypre_lapack.h"
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#include "f2c.h"
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/* Subroutine */ int dlabad_(doublereal *small, doublereal *large)
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{
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/* -- LAPACK auxiliary routine (version 3.0) --
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Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
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Courant Institute, Argonne National Lab, and Rice University
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October 31, 1992
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Purpose
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=======
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DLABAD takes as input the values computed by DLAMCH for underflow and
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overflow, and returns the square root of each of these values if the
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log of LARGE is sufficiently large. This subroutine is intended to
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identify machines with a large exponent range, such as the Crays, and
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redefine the underflow and overflow limits to be the square roots of
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the values computed by DLAMCH. This subroutine is needed because
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DLAMCH does not compensate for poor arithmetic in the upper half of
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the exponent range, as is found on a Cray.
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Arguments
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=========
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SMALL (input/output) DOUBLE PRECISION
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On entry, the underflow threshold as computed by DLAMCH.
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On exit, if LOG10(LARGE) is sufficiently large, the square
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root of SMALL, otherwise unchanged.
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LARGE (input/output) DOUBLE PRECISION
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On entry, the overflow threshold as computed by DLAMCH.
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On exit, if LOG10(LARGE) is sufficiently large, the square
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root of LARGE, otherwise unchanged.
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=====================================================================
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If it looks like we're on a Cray, take the square root of
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SMALL and LARGE to avoid overflow and underflow problems. */
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/* Builtin functions */
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double d_lg10(doublereal *), sqrt(doublereal);
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if (d_lg10(large) > 2e3) {
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*small = sqrt(*small);
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*large = sqrt(*large);
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}
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return 0;
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/* End of DLABAD */
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} /* dlabad_ */
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