complex16SYauxiliary(3)
โจ complex16SYauxiliary โจ
okay bestie, welcome to LAPACK โ this is complex16SYauxiliary(3), the complex16 auxiliary girlies. yes, that's the manual name, and yes, you're gonna know it by heart by the time we're done ๐
๐ NAME ๐
complex16SYauxiliary โ complex16. that's it, that's the name. short, sweet, iconic. ๐ฆ
๐ธ SYNOPSIS ๐ธ
Functions
subroutine zlaesy (A, B, C, RT1, RT2, EVSCAL, CS1, SN1)โ ZLAESY computes the eigenvalues and eigenvectors of a 2-by-2 complex symmetric matrix.double precision function zlansy (NORM, UPLO, N, A, LDA, WORK)โ ZLANSY returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a complex symmetric matrix.subroutine zlaqsy (UPLO, N, A, LDA, S, SCOND, AMAX, EQUED)โ ZLAQSY scales a symmetric/Hermitian matrix, using scaling factors computed by spoequ.subroutine zsymv (UPLO, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY)โ ZSYMV computes a matrix-vector product for a complex symmetric matrix.subroutine zsyr (UPLO, N, ALPHA, X, INCX, A, LDA)โ ZSYR performs the symmetric rank-1 update of a complex symmetric matrix.subroutine zsyswapr (UPLO, N, A, LDA, I1, I2)โ ZSYSWAPRsubroutine ztgsy2 (TRANS, IJOB, M, N, A, LDA, B, LDB, C, LDC, D, LDD, E, LDE, F, LDF, SCALE, RDSUM, RDSCAL, INFO)โ ZTGSY2 solves the generalized Sylvester equation (unblocked algorithm).
๐ Detailed Description ๐
This is the group of complex16 auxiliary functions for SY matrices. periodt. ๐ซถ
๐ Function Documentation ๐
โญ subroutine zlaesy (complex*16 A, complex*16 B, complex*16 C, complex*16 RT1, complex*16 RT2, complex*16 EVSCAL, complex*16 CS1, complex*16 SN1) โญ
ZLAESY computes the eigenvalues and eigenvectors of a 2-by-2 complex symmetric matrix. baby matrix energy but it's doing the most.
Purpose:
ZLAESY computes the eigendecomposition of a 2-by-2 symmetric matrix
( ( A, B );( B, C ) )
provided the norm of the matrix of eigenvectors is larger than some threshold value.
RT1 is the eigenvalue of larger absolute value, and RT2 of smaller absolute value. If the eigenvectors are computed, then on return ( CS1, SN1 ) is the unit eigenvector for RT1, hence
[ CS1 SN1 ] . [ A B ] . [ CS1 -SN1 ] = [ RT1 0 ]
[ -SN1 CS1 ] [ B C ] [ SN1 CS1 ] [ 0 RT2 ]
Parameters
AAisCOMPLEX*16- The
( 1, 1 )element of input matrix.
BBisCOMPLEX*16- The
( 1, 2 )element of input matrix. The( 2, 1 )element is also given byB, since the 2-by-2 matrix is symmetric.
CCisCOMPLEX*16- The
( 2, 2 )element of input matrix.
RT1RT1isCOMPLEX*16- The eigenvalue of larger modulus.
RT2RT2isCOMPLEX*16- The eigenvalue of smaller modulus.
EVSCALEVSCALisCOMPLEX*16- The complex value by which the eigenvector matrix was scaled to make it orthonormal. If
EVSCALis zero, the eigenvectors were not computed. This means one of two things: the 2-by-2 matrix could not be diagonalized, or the norm of the matrix of eigenvectors before scaling was larger than the threshold valueTHRESH(set below).
CS1CS1isCOMPLEX*16
SN1SN1isCOMPLEX*16- If
EVSCAL .NE. 0,( CS1, SN1 )is the unit right eigenvector forRT1.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
๐ double precision function zlansy (character NORM, character UPLO, integer N, complex*16, dimension( lda, * ) A, integer LDA, double precision, dimension( * ) WORK) ๐
ZLANSY returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a complex symmetric matrix. it's the norm girlie, she does all the norms ๐
Purpose:
ZLANSY returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a complex symmetric matrix A.
Returns
ZLANSY = ( 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.
Parameters
NORMNORMisCHARACTER*1- Specifies the value to be returned in
ZLANSYas described above.
UPLOUPLOisCHARACTER*1- Specifies whether the upper or lower triangular part of the symmetric matrix
Ais to be referenced. = 'U': Upper triangular part ofAis referenced= 'L': Lower triangular part ofAis referenced
NNisINTEGER- The order of the matrix
A.N >= 0. WhenN = 0,ZLANSYis set to zero.
AAisCOMPLEX*16array, dimension(LDA,N)- The symmetric matrix
A. IfUPLO = 'U', the leading n by n upper triangular part ofAcontains the upper triangular part of the matrixA, and the strictly lower triangular part ofAis not referenced. IfUPLO = 'L', the leading n by n lower triangular part ofAcontains the lower triangular part of the matrixA, and the strictly upper triangular part ofAis not referenced.
LDALDAisINTEGER- The leading dimension of the array
A.LDA >= max(N,1).
WORKWORKisDOUBLE PRECISIONarray, dimension(MAX(1,LWORK)), whereLWORK >= NwhenNORM = 'I'or'1'or'O'; otherwise,WORKis not referenced.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
๐ฆ subroutine zlaqsy (character UPLO, integer N, complex*16, dimension( lda, * ) A, integer LDA, double precision, dimension( * ) S, double precision SCOND, double precision AMAX, character EQUED) ๐ฆ
ZLAQSY scales a symmetric/Hermitian matrix, using scaling factors computed by spoequ. glow-up via scaling, no cap. โจ
Purpose:
ZLAQSY equilibrates a symmetric matrix A using the scaling factors in the vector S.
Parameters
UPLOUPLOisCHARACTER*1- Specifies whether the upper or lower triangular part of the symmetric matrix
Ais stored. = 'U': Upper triangular= 'L': Lower triangular
NNisINTEGER- The order of the matrix
A.N >= 0.
AAisCOMPLEX*16array, dimension(LDA,N)- On entry, the symmetric matrix
A. IfUPLO = 'U', the leading n by n upper triangular part ofAcontains the upper triangular part of the matrixA, and the strictly lower triangular part ofAis not referenced. IfUPLO = 'L', the leading n by n lower triangular part ofAcontains the lower triangular part of the matrixA, and the strictly upper triangular part ofAis not referenced. - On exit, if
EQUED = 'Y', the equilibrated matrix:diag(S) * A * diag(S).
LDALDAisINTEGER- The leading dimension of the array
A.LDA >= max(N,1).
SSisDOUBLE PRECISIONarray, dimension(N)- The scale factors for
A.
SCONDSCONDisDOUBLE PRECISION- Ratio of the smallest
S(i)to the largestS(i).
AMAXAMAXisDOUBLE PRECISION- Absolute value of largest matrix entry.
EQUEDEQUEDisCHARACTER*1- Specifies whether or not equilibration was done.
= 'N': No equilibration.= 'Y': Equilibration was done, i.e.,Ahas been replaced bydiag(S) * A * diag(S).
Internal Parameters:
THRESH is a threshold value used to decide if scaling should be done based on the ratio of the scaling factors. If SCOND < THRESH, scaling is done.
LARGE and SMALL are threshold values used to decide if scaling should be done based on the absolute size of the largest matrix element. If AMAX > LARGE or AMAX < SMALL, scaling is done.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
๐ฅ subroutine zsymv (character UPLO, integer N, complex*16 ALPHA, complex*16, dimension( lda, * ) A, integer LDA, complex*16, dimension( * ) X, integer INCX, complex*16 BETA, complex*16, dimension( * ) Y, integer INCY) ๐ฅ
ZSYMV computes a matrix-vector product for a complex symmetric matrix. matvec but make it symmetric, slay. ๐
Purpose:
ZSYMV performs the matrix-vector operation
y := alpha*A*x + beta*y,
where alpha and beta are scalars, x and y are n element vectors and A is an n by n symmetric matrix.
Parameters
UPLOUPLOisCHARACTER*1- On entry,
UPLOspecifies whether the upper or lower triangular part of the arrayAis to be referenced as follows:
UPLO = 'U' or 'u' Only the upper triangular part of A
is to be referenced.
UPLO = 'L' or 'l' Only the lower triangular part of A
is to be referenced.
- Unchanged on exit.
NNisINTEGER- On entry,
Nspecifies the order of the matrixA.Nmust be at least zero. Unchanged on exit.
ALPHAALPHAisCOMPLEX*16- On entry,
ALPHAspecifies the scalar alpha. Unchanged on exit.
A
bestie, A's description got cut off right here โ this is part 1 of 3 and the rest is coming, don't go anywhere ๐ซถ
A
Ais aCOMPLEX*16array, dimension( LDA, N ). Okay bestie, listen up: before entry, withUPLO = 'U'or'u', the leadingnbynupper triangular part of the arrayAmust contain the upper triangular part of the symmetric matrix and the strictly lower triangular part ofAis not referenced. Before entry, withUPLO = 'L'or'l', the leadingnbynlower triangular part of the arrayAmust contain the lower triangular part of the symmetric matrix and the strictly upper triangular part ofAis not referenced. Unchanged on exit. ๐
LDA
LDAisINTEGER. On entry,LDAspecifies the first dimension ofAas declared in the calling (sub) program.LDAmust be at leastmax( 1, N ). Unchanged on exit. โจ
X
Xis aCOMPLEX*16array, dimension at least( 1 + ( N - 1 )*abs( INCX ) ). Before entry, the incremented arrayXmust contain theN-element vectorx. Unchanged on exit. ๐ฆ
INCX
INCXisINTEGER. On entry,INCXspecifies the increment for the elements ofX.INCXmust not be zero. Unchanged on exit. ๐
BETA
BETAisCOMPLEX*16. On entry,BETAspecifies the scalar beta. WhenBETAis supplied as zero thenYneed not be set on input. Unchanged on exit. ๐ธ
Y
Yis aCOMPLEX*16array, dimension at least( 1 + ( N - 1 )*abs( INCY ) ). Before entry, the incremented arrayYmust contain thenelement vectory. On exit,Yis overwritten by the updated vectory. ๐ฅ
INCY
INCYisINTEGER. On entry,INCYspecifies the increment for the elements ofY.INCYmust not be zero. Unchanged on exit. ๐
Author
- Univ. of Tennessee
- Univ. of California Berkeley
- Univ. of Colorado Denver
- NAG Ltd.
subroutine zsyr
subroutine zsyr (character UPLO, integer N, complex*16 ALPHA, complex*16,
dimension( * ) X, integer INCX, complex*16, dimension( lda, * ) A,
integer LDA)
ZSYR performs the symmetric rank-1 update of a complex symmetric matrix. Periodt. ๐
Purpose
ZSYR performs the symmetric rank 1 operation
A := alpha*x*x**H + A,
where alpha is a complex scalar, x is an n element vector and A is an n by n symmetric matrix. Slay. โจ
Parameters
UPLOisCHARACTER*1. On entry,UPLOspecifies whether the upper or lower triangular part of the arrayAis to be referenced as follows:UPLO = 'U'or'u'โ Only the upper triangular part ofAis to be referenced.UPLO = 'L'or'l'โ Only the lower triangular part ofAis to be referenced. Unchanged on exit. ๐
NisINTEGER. On entry,Nspecifies the order of the matrixA.Nmust be at least zero. Unchanged on exit. ๐ALPHAisCOMPLEX*16. On entry,ALPHAspecifies the scalar alpha. Unchanged on exit. ๐Xis aCOMPLEX*16array, dimension at least( 1 + ( N - 1 )*abs( INCX ) ). Before entry, the incremented arrayXmust contain theN-element vectorx. Unchanged on exit. ๐ฆINCXisINTEGER. On entry,INCXspecifies the increment for the elements ofX.INCXmust not be zero. Unchanged on exit. ๐Ais aCOMPLEX*16array, dimension( LDA, N ). Before entry, withUPLO = 'U'or'u', the leadingnbynupper triangular part of the arrayAmust contain the upper triangular part of the symmetric matrix and the strictly lower triangular part ofAis not referenced. On exit, the upper triangular part of the arrayAis overwritten by the upper triangular part of the updated matrix. Before entry, withUPLO = 'L'or'l', the leadingnbynlower triangular part of the arrayAmust contain the lower triangular part of the symmetric matrix and the strictly upper triangular part ofAis not referenced. On exit, the lower triangular part of the arrayAis overwritten by the lower triangular part of the updated matrix. ๐ฅLDAisINTEGER. On entry,LDAspecifies the first dimension ofAas declared in the calling (sub) program.LDAmust be at leastmax( 1, N ). Unchanged on exit. โจ
Author
- Univ. of Tennessee
- Univ. of California Berkeley
- Univ. of Colorado Denver
- NAG Ltd.
subroutine zsyswapr
subroutine zsyswapr (character UPLO, integer N, complex*16, dimension( lda,
* ) A, integer LDA, integer I1, integer I2)
ZSYSWAPR applies an elementary permutation on the rows and the columns of a symmetric matrix. ๐
Purpose
ZSYSWAPR applies an elementary permutation on the rows and the columns of a symmetric matrix. ๐ซ
Parameters
UPLOisCHARACTER*1. Specifies whether the details of the factorization are stored as an upper or lower triangular matrix.= 'U': Upper triangular, form isA = U*D*U**T;= 'L': Lower triangular, form isA = L*D*L**T. ๐
NisINTEGER. The order of the matrixA.N >= 0. โจAis aCOMPLEX*16array, dimension(LDA,*). On entry, theN-by-NmatrixA. On exit, the permuted matrix where the rowsI1andI2and columnsI1andI2are interchanged. IfUPLO = 'U', the interchanges are applied to the upper triangular part and the strictly lower triangular part ofAis not referenced; ifUPLO = 'L', the interchanges are applied to the lower triangular part and the part ofAabove the diagonal is not referenced. ๐ฆLDAisINTEGER. The leading dimension of the arrayA.LDA >= max(1,N). ๐I1isINTEGER. Index of the first row to swap. ๐I2isINTEGER. Index of the second row to swap. ๐
Author
- Univ. of Tennessee
- Univ. of California Berkeley
- Univ. of Colorado Denver
- NAG Ltd.
subroutine ztgsy2
subroutine ztgsy2 (character TRANS, integer IJOB, integer M, integer N,
complex*16, dimension( lda, * ) A, integer LDA, complex*16, dimension(
ldb, * ) B, integer LDB, complex*16, dimension( ldc, * ) C, integer LDC,
complex*16, dimension( ldd, * ) D, integer LDD, complex*16, dimension(
lde, * ) E, integer LDE, complex*16, dimension( ldf, * ) F, integer LDF,
double precision SCALE, double precision RDSUM, double precision RDSCAL,
integer INFO)
ZTGSY2 solves the generalized Sylvester equation (unblocked algorithm). Iconic. ๐
Purpose
ZTGSY2 solves the generalized Sylvester equation
A * R - L * B = scale * C (1)
D * R - L * E = scale * F
using Level 1 and 2 BLAS, where R and L are unknown M-by-N matrices, (A, D), (B, E) and (C, F) are given matrix pairs of size M-by-M, N-by-N and M-by-N, respectively. A, B, D and E are upper triangular (i.e., (A,D) and (B,E) in generalized Schur form). ๐
The solution (R, L) overwrites (C, F). 0 <= SCALE <= 1 is an output scaling factor chosen to avoid overflow. ๐
In matrix notation solving equation (1) corresponds to solve Zx = scale * b, where Z is defined as
Z = [ kron(In, A) -kron(B**H, Im) ] (2)
[ kron(In, D) -kron(E**H, Im) ],
Ik is the identity matrix of size k and X**H is the conjuguate transpose of X. kron(X, Y) is the Kronecker product between the matrices X and Y. ๐งฎ
If TRANS = 'C', y in the conjugate transposed system Z**H*y = scale*b is solved for, which is equivalent to solve for R and L in
A**H * R + D**H * L = scale * C (3)
R * B**H + L * E**H = scale * -F
This case is used to compute an estimate of Dif[(A, D), (B, E)] = = sigma_min(Z) using reverse communication with ZLACON. ๐
ZTGSY2 also (IJOB >= 1) contributes to the computation in ZTGSYL of an upper bound on the separation between to matrix pairs. Then the input (A, D), (B, E) are sub-pencils of two matrix pairs in ZTGSYL. ๐
Parameters
TRANSisCHARACTER*1.= 'N': solve the generalized Sylvester equation (1).= 'T': solve the 'transposed' system (3). ๐
IJOBisINTEGER. Specifies what kind of functionality to be performed.=0: solve (1) only.=1: A contribution from this subsystem to a Frobenius norm-based estimate of the separation between two matrix pairs is computed. (look ahead strategy is used).=2: A contribution from this subsystem to a Frobenius norm-based estimate of the separation between two matrix pairs is computed. (DGECON on sub-systems is used). Not referenced ifTRANS = 'T'. ๐ฏ
MisINTEGER. On entry,Mspecifies the order ofAandD, and the row dimension ofC,F,RandL. ๐NisINTEGER. On entry,Nspecifies the order ofBandE, and the column dimension ofC,F,RandL. ๐Ais aCOMPLEX*16array, dimension(LDA, M). On entry,Acontains an upper triangular matrix. ๐บLDAisINTEGER. The leading dimension of the matrixA.LDA >= max(1, M). ๐Bis aCOMPLEX*16array, dimension(LDB, N). On entry,Bcontains an upper triangular matrix. ๐บLDBisINTEGER. The leading dimension of the matrixB.LDB >= max(1, N). ๐CCโ COMPLEX*16 array, dimension(LDC, N). On entry, bestie,Cis holding the right-hand-side of the first matrix equation in (1). On exit, ifIJOB = 0,Chas been overwritten by the solutionR. ๐ She's a working girl, she gets repurposed.LDCโ INTEGER. The leading dimension of the matrixC. And the rule isLDC >= max(1, M). No exceptions, no negotiating. ๐Dโ COMPLEX*16 array, dimension(LDD, M). On entry,Dcontains an upper triangular matrix. That's it, that's her whole job. โจLDDโ INTEGER. The leading dimension of the matrixD.LDD >= max(1, M). Periodt. ๐ฆEโ COMPLEX*16 array, dimension(LDE, N). On entry,Econtains an upper triangular matrix. Upper triangular icon behavior, honestly. ๐ธLDEโ INTEGER. The leading dimension of the matrixE.LDE >= max(1, N). Note it'sNhere, notMโ she's different, she's special. ๐Fโ COMPLEX*16 array, dimension(LDF, N). On entry,Fcontains the right-hand-side of the second matrix equation in (1). On exit, ifIJOB = 0,Fhas been overwritten by the solutionL. Yes she'sFand she becomesL, don't think about it too hard, it's giving transformation arc. ๐งLDFโ INTEGER. The leading dimension of the matrixF.LDF >= max(1, M). (Yeah,Mโ she really said "I'm not likeLDE".) ๐SCALEโ DOUBLE PRECISION. On exit,0 <= SCALE <= 1. Okay so if0 < SCALE < 1, the solutionsRandL(which wereCandFon entry, iykyk) will hold the solutions to a slightly perturbed system, but the input matricesA,B,DandEhave not been changed. IfSCALE = 0, thenRandLwill hold the solutions to the homogeneous system withC = F = 0. And normally?SCALE = 1. Chill, standard, no drama. ๐RDSUMโ DOUBLE PRECISION. On entry, this is the sum of squares of computed contributions to the Dif-estimate under computation byZTGSYL, where the scaling factorRDSCAL(see below bestie, I got you) has been factored out. On exit, the corresponding sum of squares updated with the contributions from the current sub-system. IfTRANS = 'T',RDSUMis not touched. And a lil NOTE for you:RDSUMonly makes sense whenZTGSY2is called byZTGSYL. ๐RDSCALโ DOUBLE PRECISION. On entry, scaling factor used to prevent overflow inRDSUM. On exit,RDSCALis updated w.r.t. the current contributions inRDSUM. IfTRANS = 'T',RDSCALis not touched. Another NOTE:RDSCALonly makes sense whenZTGSY2is called byZTGSYL. Same energy, different variable. ๐INFOโ INTEGER. On exit, ifINFOis set to:=0: Successful exit. Slay. โ<0: IfINFO = -i, input argument number i is illegal. Somebody passed something cursed and she's telling on you. ๐>0: The matrix pairs(A, D)and(B, E)have common or very close eigenvalues. Not an error exactly, justโฆ complicated. ๐ญ
๐ Author ๐
- Univ. of Tennessee
- Univ. of California Berkeley
- Univ. of Colorado Denver
- NAG Ltd.
๐ซถ Contributors:
Bo Kagstrom and Peter Poromaa, Department of Computing Science, Umea University, S-901 87 Umea, Sweden. Legends, fr fr. ๐
Author โจ
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