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OpenBLAS/lapack-netlib/SRC/dlantr.f

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*> \brief \b DLANTR returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a trapezoidal or triangular matrix.
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download DLANTR + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlantr.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlantr.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlantr.f">
*> [TXT]</a>
*> \endhtmlonly
*
* Definition:
* ===========
*
* DOUBLE PRECISION FUNCTION DLANTR( NORM, UPLO, DIAG, M, N, A, LDA,
* WORK )
*
* .. Scalar Arguments ..
* CHARACTER DIAG, NORM, UPLO
* INTEGER LDA, M, N
* ..
* .. Array Arguments ..
* DOUBLE PRECISION A( LDA, * ), WORK( * )
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> DLANTR returns the value of the one norm, or the Frobenius norm, or
*> the infinity norm, or the element of largest absolute value of a
*> trapezoidal or triangular matrix A.
*> \endverbatim
*>
*> \return DLANTR
*> \verbatim
*>
*> DLANTR = ( max(abs(A(i,j))), NORM = 'M' or 'm'
*> (
*> ( norm1(A), NORM = '1', 'O' or 'o'
*> (
*> ( normI(A), NORM = 'I' or 'i'
*> (
*> ( normF(A), NORM = 'F', 'f', 'E' or 'e'
*>
*> where norm1 denotes the one norm of a matrix (maximum column sum),
*> normI denotes the infinity norm of a matrix (maximum row sum) and
*> normF denotes the Frobenius norm of a matrix (square root of sum of
*> squares). Note that max(abs(A(i,j))) is not a consistent matrix norm.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] NORM
*> \verbatim
*> NORM is CHARACTER*1
*> Specifies the value to be returned in DLANTR as described
*> above.
*> \endverbatim
*>
*> \param[in] UPLO
*> \verbatim
*> UPLO is CHARACTER*1
*> Specifies whether the matrix A is upper or lower trapezoidal.
*> = 'U': Upper trapezoidal
*> = 'L': Lower trapezoidal
*> Note that A is triangular instead of trapezoidal if M = N.
*> \endverbatim
*>
*> \param[in] DIAG
*> \verbatim
*> DIAG is CHARACTER*1
*> Specifies whether or not the matrix A has unit diagonal.
*> = 'N': Non-unit diagonal
*> = 'U': Unit diagonal
*> \endverbatim
*>
*> \param[in] M
*> \verbatim
*> M is INTEGER
*> The number of rows of the matrix A. M >= 0, and if
*> UPLO = 'U', M <= N. When M = 0, DLANTR is set to zero.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> The number of columns of the matrix A. N >= 0, and if
*> UPLO = 'L', N <= M. When N = 0, DLANTR is set to zero.
*> \endverbatim
*>
*> \param[in] A
*> \verbatim
*> A is DOUBLE PRECISION array, dimension (LDA,N)
*> The trapezoidal matrix A (A is triangular if M = N).
*> If UPLO = 'U', the leading m by n upper trapezoidal part of
*> the array A contains the upper trapezoidal matrix, and the
*> strictly lower triangular part of A is not referenced.
*> If UPLO = 'L', the leading m by n lower trapezoidal part of
*> the array A contains the lower trapezoidal matrix, and the
*> strictly upper triangular part of A is not referenced. Note
*> that when DIAG = 'U', the diagonal elements of A are not
*> referenced and are assumed to be one.
*> \endverbatim
*>
*> \param[in] LDA
*> \verbatim
*> LDA is INTEGER
*> The leading dimension of the array A. LDA >= max(M,1).
*> \endverbatim
*>
*> \param[out] WORK
*> \verbatim
*> WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK)),
*> where LWORK >= M when NORM = 'I'; otherwise, WORK is not
*> referenced.
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date September 2012
*
*> \ingroup doubleOTHERauxiliary
*
* =====================================================================
DOUBLE PRECISION FUNCTION DLANTR( NORM, UPLO, DIAG, M, N, A, LDA,
$ WORK )
*
* -- LAPACK auxiliary routine (version 3.4.2) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* September 2012
*
* .. Scalar Arguments ..
CHARACTER DIAG, NORM, UPLO
INTEGER LDA, M, N
* ..
* .. Array Arguments ..
DOUBLE PRECISION A( LDA, * ), WORK( * )
* ..
*
* =====================================================================
*
* .. Parameters ..
DOUBLE PRECISION ONE, ZERO
PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 )
* ..
* .. Local Scalars ..
LOGICAL UDIAG
INTEGER I, J
DOUBLE PRECISION SCALE, SUM, VALUE
* ..
* .. External Subroutines ..
EXTERNAL DLASSQ
* ..
* .. External Functions ..
LOGICAL LSAME, DISNAN
EXTERNAL LSAME, DISNAN
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS, MIN, SQRT
* ..
* .. Executable Statements ..
*
IF( MIN( M, N ).EQ.0 ) THEN
VALUE = ZERO
ELSE IF( LSAME( NORM, 'M' ) ) THEN
*
* Find max(abs(A(i,j))).
*
IF( LSAME( DIAG, 'U' ) ) THEN
VALUE = ONE
IF( LSAME( UPLO, 'U' ) ) THEN
DO 20 J = 1, N
DO 10 I = 1, MIN( M, J-1 )
SUM = ABS( A( I, J ) )
IF( VALUE .LT. SUM .OR. DISNAN( SUM ) ) VALUE = SUM
10 CONTINUE
20 CONTINUE
ELSE
DO 40 J = 1, N
DO 30 I = J + 1, M
SUM = ABS( A( I, J ) )
IF( VALUE .LT. SUM .OR. DISNAN( SUM ) ) VALUE = SUM
30 CONTINUE
40 CONTINUE
END IF
ELSE
VALUE = ZERO
IF( LSAME( UPLO, 'U' ) ) THEN
DO 60 J = 1, N
DO 50 I = 1, MIN( M, J )
SUM = ABS( A( I, J ) )
IF( VALUE .LT. SUM .OR. DISNAN( SUM ) ) VALUE = SUM
50 CONTINUE
60 CONTINUE
ELSE
DO 80 J = 1, N
DO 70 I = J, M
SUM = ABS( A( I, J ) )
IF( VALUE .LT. SUM .OR. DISNAN( SUM ) ) VALUE = SUM
70 CONTINUE
80 CONTINUE
END IF
END IF
ELSE IF( ( LSAME( NORM, 'O' ) ) .OR. ( NORM.EQ.'1' ) ) THEN
*
* Find norm1(A).
*
VALUE = ZERO
UDIAG = LSAME( DIAG, 'U' )
IF( LSAME( UPLO, 'U' ) ) THEN
DO 110 J = 1, N
IF( ( UDIAG ) .AND. ( J.LE.M ) ) THEN
SUM = ONE
DO 90 I = 1, J - 1
SUM = SUM + ABS( A( I, J ) )
90 CONTINUE
ELSE
SUM = ZERO
DO 100 I = 1, MIN( M, J )
SUM = SUM + ABS( A( I, J ) )
100 CONTINUE
END IF
IF( VALUE .LT. SUM .OR. DISNAN( SUM ) ) VALUE = SUM
110 CONTINUE
ELSE
DO 140 J = 1, N
IF( UDIAG ) THEN
SUM = ONE
DO 120 I = J + 1, M
SUM = SUM + ABS( A( I, J ) )
120 CONTINUE
ELSE
SUM = ZERO
DO 130 I = J, M
SUM = SUM + ABS( A( I, J ) )
130 CONTINUE
END IF
IF( VALUE .LT. SUM .OR. DISNAN( SUM ) ) VALUE = SUM
140 CONTINUE
END IF
ELSE IF( LSAME( NORM, 'I' ) ) THEN
*
* Find normI(A).
*
IF( LSAME( UPLO, 'U' ) ) THEN
IF( LSAME( DIAG, 'U' ) ) THEN
DO 150 I = 1, M
WORK( I ) = ONE
150 CONTINUE
DO 170 J = 1, N
DO 160 I = 1, MIN( M, J-1 )
WORK( I ) = WORK( I ) + ABS( A( I, J ) )
160 CONTINUE
170 CONTINUE
ELSE
DO 180 I = 1, M
WORK( I ) = ZERO
180 CONTINUE
DO 200 J = 1, N
DO 190 I = 1, MIN( M, J )
WORK( I ) = WORK( I ) + ABS( A( I, J ) )
190 CONTINUE
200 CONTINUE
END IF
ELSE
IF( LSAME( DIAG, 'U' ) ) THEN
DO 210 I = 1, N
WORK( I ) = ONE
210 CONTINUE
DO 220 I = N + 1, M
WORK( I ) = ZERO
220 CONTINUE
DO 240 J = 1, N
DO 230 I = J + 1, M
WORK( I ) = WORK( I ) + ABS( A( I, J ) )
230 CONTINUE
240 CONTINUE
ELSE
DO 250 I = 1, M
WORK( I ) = ZERO
250 CONTINUE
DO 270 J = 1, N
DO 260 I = J, M
WORK( I ) = WORK( I ) + ABS( A( I, J ) )
260 CONTINUE
270 CONTINUE
END IF
END IF
VALUE = ZERO
DO 280 I = 1, M
SUM = WORK( I )
IF( VALUE .LT. SUM .OR. DISNAN( SUM ) ) VALUE = SUM
280 CONTINUE
ELSE IF( ( LSAME( NORM, 'F' ) ) .OR. ( LSAME( NORM, 'E' ) ) ) THEN
*
* Find normF(A).
*
IF( LSAME( UPLO, 'U' ) ) THEN
IF( LSAME( DIAG, 'U' ) ) THEN
SCALE = ONE
SUM = MIN( M, N )
DO 290 J = 2, N
CALL DLASSQ( MIN( M, J-1 ), A( 1, J ), 1, SCALE, SUM )
290 CONTINUE
ELSE
SCALE = ZERO
SUM = ONE
DO 300 J = 1, N
CALL DLASSQ( MIN( M, J ), A( 1, J ), 1, SCALE, SUM )
300 CONTINUE
END IF
ELSE
IF( LSAME( DIAG, 'U' ) ) THEN
SCALE = ONE
SUM = MIN( M, N )
DO 310 J = 1, N
CALL DLASSQ( M-J, A( MIN( M, J+1 ), J ), 1, SCALE,
$ SUM )
310 CONTINUE
ELSE
SCALE = ZERO
SUM = ONE
DO 320 J = 1, N
CALL DLASSQ( M-J+1, A( J, J ), 1, SCALE, SUM )
320 CONTINUE
END IF
END IF
VALUE = SCALE*SQRT( SUM )
END IF
*
DLANTR = VALUE
RETURN
*
* End of DLANTR
*
END
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