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Diffstat (limited to '2.3-1/src/fortran/lapack/dopgtr.f')
| -rw-r--r-- | 2.3-1/src/fortran/lapack/dopgtr.f | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/2.3-1/src/fortran/lapack/dopgtr.f b/2.3-1/src/fortran/lapack/dopgtr.f new file mode 100644 index 00000000..cf0901ff --- /dev/null +++ b/2.3-1/src/fortran/lapack/dopgtr.f @@ -0,0 +1,160 @@ + SUBROUTINE DOPGTR( UPLO, N, AP, TAU, Q, LDQ, WORK, INFO ) +* +* -- LAPACK routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER UPLO + INTEGER INFO, LDQ, N +* .. +* .. Array Arguments .. + DOUBLE PRECISION AP( * ), Q( LDQ, * ), TAU( * ), WORK( * ) +* .. +* +* Purpose +* ======= +* +* DOPGTR generates a real orthogonal matrix Q which is defined as the +* product of n-1 elementary reflectors H(i) of order n, as returned by +* DSPTRD using packed storage: +* +* if UPLO = 'U', Q = H(n-1) . . . H(2) H(1), +* +* if UPLO = 'L', Q = H(1) H(2) . . . H(n-1). +* +* Arguments +* ========= +* +* UPLO (input) CHARACTER*1 +* = 'U': Upper triangular packed storage used in previous +* call to DSPTRD; +* = 'L': Lower triangular packed storage used in previous +* call to DSPTRD. +* +* N (input) INTEGER +* The order of the matrix Q. N >= 0. +* +* AP (input) DOUBLE PRECISION array, dimension (N*(N+1)/2) +* The vectors which define the elementary reflectors, as +* returned by DSPTRD. +* +* TAU (input) DOUBLE PRECISION array, dimension (N-1) +* TAU(i) must contain the scalar factor of the elementary +* reflector H(i), as returned by DSPTRD. +* +* Q (output) DOUBLE PRECISION array, dimension (LDQ,N) +* The N-by-N orthogonal matrix Q. +* +* LDQ (input) INTEGER +* The leading dimension of the array Q. LDQ >= max(1,N). +* +* WORK (workspace) DOUBLE PRECISION array, dimension (N-1) +* +* INFO (output) INTEGER +* = 0: successful exit +* < 0: if INFO = -i, the i-th argument had an illegal value +* +* ===================================================================== +* +* .. Parameters .. + DOUBLE PRECISION ZERO, ONE + PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 ) +* .. +* .. Local Scalars .. + LOGICAL UPPER + INTEGER I, IINFO, IJ, J +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. External Subroutines .. + EXTERNAL DORG2L, DORG2R, XERBLA +* .. +* .. Intrinsic Functions .. + INTRINSIC MAX +* .. +* .. Executable Statements .. +* +* Test the input arguments +* + INFO = 0 + UPPER = LSAME( UPLO, 'U' ) + IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN + INFO = -1 + ELSE IF( N.LT.0 ) THEN + INFO = -2 + ELSE IF( LDQ.LT.MAX( 1, N ) ) THEN + INFO = -6 + END IF + IF( INFO.NE.0 ) THEN + CALL XERBLA( 'DOPGTR', -INFO ) + RETURN + END IF +* +* Quick return if possible +* + IF( N.EQ.0 ) + $ RETURN +* + IF( UPPER ) THEN +* +* Q was determined by a call to DSPTRD with UPLO = 'U' +* +* Unpack the vectors which define the elementary reflectors and +* set the last row and column of Q equal to those of the unit +* matrix +* + IJ = 2 + DO 20 J = 1, N - 1 + DO 10 I = 1, J - 1 + Q( I, J ) = AP( IJ ) + IJ = IJ + 1 + 10 CONTINUE + IJ = IJ + 2 + Q( N, J ) = ZERO + 20 CONTINUE + DO 30 I = 1, N - 1 + Q( I, N ) = ZERO + 30 CONTINUE + Q( N, N ) = ONE +* +* Generate Q(1:n-1,1:n-1) +* + CALL DORG2L( N-1, N-1, N-1, Q, LDQ, TAU, WORK, IINFO ) +* + ELSE +* +* Q was determined by a call to DSPTRD with UPLO = 'L'. +* +* Unpack the vectors which define the elementary reflectors and +* set the first row and column of Q equal to those of the unit +* matrix +* + Q( 1, 1 ) = ONE + DO 40 I = 2, N + Q( I, 1 ) = ZERO + 40 CONTINUE + IJ = 3 + DO 60 J = 2, N + Q( 1, J ) = ZERO + DO 50 I = J + 1, N + Q( I, J ) = AP( IJ ) + IJ = IJ + 1 + 50 CONTINUE + IJ = IJ + 2 + 60 CONTINUE + IF( N.GT.1 ) THEN +* +* Generate Q(2:n,2:n) +* + CALL DORG2R( N-1, N-1, N-1, Q( 2, 2 ), LDQ, TAU, WORK, + $ IINFO ) + END IF + END IF + RETURN +* +* End of DOPGTR +* + END |