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Diffstat (limited to 'src/fortran/lapack/zungtr.f')
| -rw-r--r-- | src/fortran/lapack/zungtr.f | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/src/fortran/lapack/zungtr.f b/src/fortran/lapack/zungtr.f new file mode 100644 index 0000000..5de7c10 --- /dev/null +++ b/src/fortran/lapack/zungtr.f @@ -0,0 +1,184 @@ + SUBROUTINE ZUNGTR( UPLO, N, A, LDA, TAU, WORK, LWORK, INFO ) +* +* -- LAPACK routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER UPLO + INTEGER INFO, LDA, LWORK, N +* .. +* .. Array Arguments .. + COMPLEX*16 A( LDA, * ), TAU( * ), WORK( * ) +* .. +* +* Purpose +* ======= +* +* ZUNGTR generates a complex unitary matrix Q which is defined as the +* product of n-1 elementary reflectors of order N, as returned by +* ZHETRD: +* +* 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 triangle of A contains elementary reflectors +* from ZHETRD; +* = 'L': Lower triangle of A contains elementary reflectors +* from ZHETRD. +* +* N (input) INTEGER +* The order of the matrix Q. N >= 0. +* +* A (input/output) COMPLEX*16 array, dimension (LDA,N) +* On entry, the vectors which define the elementary reflectors, +* as returned by ZHETRD. +* On exit, the N-by-N unitary matrix Q. +* +* LDA (input) INTEGER +* The leading dimension of the array A. LDA >= N. +* +* TAU (input) COMPLEX*16 array, dimension (N-1) +* TAU(i) must contain the scalar factor of the elementary +* reflector H(i), as returned by ZHETRD. +* +* WORK (workspace/output) COMPLEX*16 array, dimension (MAX(1,LWORK)) +* On exit, if INFO = 0, WORK(1) returns the optimal LWORK. +* +* LWORK (input) INTEGER +* The dimension of the array WORK. LWORK >= N-1. +* For optimum performance LWORK >= (N-1)*NB, where NB is +* the optimal blocksize. +* +* If LWORK = -1, then a workspace query is assumed; the routine +* only calculates the optimal size of the WORK array, returns +* this value as the first entry of the WORK array, and no error +* message related to LWORK is issued by XERBLA. +* +* INFO (output) INTEGER +* = 0: successful exit +* < 0: if INFO = -i, the i-th argument had an illegal value +* +* ===================================================================== +* +* .. Parameters .. + COMPLEX*16 ZERO, ONE + PARAMETER ( ZERO = ( 0.0D+0, 0.0D+0 ), + $ ONE = ( 1.0D+0, 0.0D+0 ) ) +* .. +* .. Local Scalars .. + LOGICAL LQUERY, UPPER + INTEGER I, IINFO, J, LWKOPT, NB +* .. +* .. External Functions .. + LOGICAL LSAME + INTEGER ILAENV + EXTERNAL LSAME, ILAENV +* .. +* .. External Subroutines .. + EXTERNAL XERBLA, ZUNGQL, ZUNGQR +* .. +* .. Intrinsic Functions .. + INTRINSIC MAX +* .. +* .. Executable Statements .. +* +* Test the input arguments +* + INFO = 0 + LQUERY = ( LWORK.EQ.-1 ) + 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( LDA.LT.MAX( 1, N ) ) THEN + INFO = -4 + ELSE IF( LWORK.LT.MAX( 1, N-1 ) .AND. .NOT.LQUERY ) THEN + INFO = -7 + END IF +* + IF( INFO.EQ.0 ) THEN + IF( UPPER ) THEN + NB = ILAENV( 1, 'ZUNGQL', ' ', N-1, N-1, N-1, -1 ) + ELSE + NB = ILAENV( 1, 'ZUNGQR', ' ', N-1, N-1, N-1, -1 ) + END IF + LWKOPT = MAX( 1, N-1 )*NB + WORK( 1 ) = LWKOPT + END IF +* + IF( INFO.NE.0 ) THEN + CALL XERBLA( 'ZUNGTR', -INFO ) + RETURN + ELSE IF( LQUERY ) THEN + RETURN + END IF +* +* Quick return if possible +* + IF( N.EQ.0 ) THEN + WORK( 1 ) = 1 + RETURN + END IF +* + IF( UPPER ) THEN +* +* Q was determined by a call to ZHETRD with UPLO = 'U' +* +* Shift the vectors which define the elementary reflectors one +* column to the left, and set the last row and column of Q to +* those of the unit matrix +* + DO 20 J = 1, N - 1 + DO 10 I = 1, J - 1 + A( I, J ) = A( I, J+1 ) + 10 CONTINUE + A( N, J ) = ZERO + 20 CONTINUE + DO 30 I = 1, N - 1 + A( I, N ) = ZERO + 30 CONTINUE + A( N, N ) = ONE +* +* Generate Q(1:n-1,1:n-1) +* + CALL ZUNGQL( N-1, N-1, N-1, A, LDA, TAU, WORK, LWORK, IINFO ) +* + ELSE +* +* Q was determined by a call to ZHETRD with UPLO = 'L'. +* +* Shift the vectors which define the elementary reflectors one +* column to the right, and set the first row and column of Q to +* those of the unit matrix +* + DO 50 J = N, 2, -1 + A( 1, J ) = ZERO + DO 40 I = J + 1, N + A( I, J ) = A( I, J-1 ) + 40 CONTINUE + 50 CONTINUE + A( 1, 1 ) = ONE + DO 60 I = 2, N + A( I, 1 ) = ZERO + 60 CONTINUE + IF( N.GT.1 ) THEN +* +* Generate Q(2:n,2:n) +* + CALL ZUNGQR( N-1, N-1, N-1, A( 2, 2 ), LDA, TAU, WORK, + $ LWORK, IINFO ) + END IF + END IF + WORK( 1 ) = LWKOPT + RETURN +* +* End of ZUNGTR +* + END |