MAGMA  1.5.0
Matrix Algebra for GPU and Multicore Architectures
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single-complex precision

Functions

magma_int_t magma_chegst (magma_int_t itype, magma_uplo_t uplo, magma_int_t n, magmaFloatComplex *A, magma_int_t lda, magmaFloatComplex *B, magma_int_t ldb, magma_int_t *info)
 CHEGST reduces a complex Hermitian-definite generalized eigenproblem to standard form. More...
 
magma_int_t magma_chegst_gpu (magma_int_t itype, magma_uplo_t uplo, magma_int_t n, magmaFloatComplex *dA, magma_int_t ldda, magmaFloatComplex *dB, magma_int_t lddb, magma_int_t *info)
 CHEGST_GPU reduces a complex Hermitian-definite generalized eigenproblem to standard form. More...
 
magma_int_t magma_chegst_m (magma_int_t nrgpu, magma_int_t itype, magma_uplo_t uplo, magma_int_t n, magmaFloatComplex *A, magma_int_t lda, magmaFloatComplex *B, magma_int_t ldb, magma_int_t *info)
 CHEGST_M reduces a complex Hermitian-definite generalized eigenproblem to standard form. More...
 
magma_int_t magma_chetrd (magma_uplo_t uplo, magma_int_t n, magmaFloatComplex *A, magma_int_t lda, float *d, float *e, magmaFloatComplex *tau, magmaFloatComplex *work, magma_int_t lwork, magma_int_t *info)
 CHETRD reduces a complex Hermitian matrix A to real symmetric tridiagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T. More...
 
magma_int_t magma_chetrd2_gpu (magma_uplo_t uplo, magma_int_t n, magmaFloatComplex *dA, magma_int_t ldda, float *d, float *e, magmaFloatComplex *tau, magmaFloatComplex *wA, magma_int_t ldwa, magmaFloatComplex *work, magma_int_t lwork, magmaFloatComplex *dwork, magma_int_t ldwork, magma_int_t *info)
 CHETRD2_GPU reduces a complex Hermitian matrix A to real symmetric tridiagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T. More...
 
magma_int_t magma_chetrd_gpu (magma_uplo_t uplo, magma_int_t n, magmaFloatComplex *dA, magma_int_t ldda, float *d, float *e, magmaFloatComplex *tau, magmaFloatComplex *wA, magma_int_t ldwa, magmaFloatComplex *work, magma_int_t lwork, magma_int_t *info)
 CHETRD_GPU reduces a complex Hermitian matrix A to real symmetric tridiagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T. More...
 
magma_int_t magma_chetrd_mgpu (magma_int_t num_gpus, magma_int_t k, magma_uplo_t uplo, magma_int_t n, magmaFloatComplex *A, magma_int_t lda, float *d, float *e, magmaFloatComplex *tau, magmaFloatComplex *work, magma_int_t lwork, magma_int_t *info)
 CHETRD reduces a complex Hermitian matrix A to real symmetric tridiagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T. More...
 
magma_int_t magma_cstedx (magma_range_t range, magma_int_t n, float vl, float vu, magma_int_t il, magma_int_t iu, float *d, float *e, magmaFloatComplex *Z, magma_int_t ldz, float *rwork, magma_int_t lrwork, magma_int_t *iwork, magma_int_t liwork, float *dwork, magma_int_t *info)
 CSTEDX computes some eigenvalues and eigenvectors of a symmetric tridiagonal matrix using the divide and conquer method. More...
 
magma_int_t magma_cstedx_m (magma_int_t nrgpu, magma_range_t range, magma_int_t n, float vl, float vu, magma_int_t il, magma_int_t iu, float *d, float *e, magmaFloatComplex *Z, magma_int_t ldz, float *rwork, magma_int_t lrwork, magma_int_t *iwork, magma_int_t liwork, magma_int_t *info)
 CSTEDX computes some eigenvalues and eigenvectors of a symmetric tridiagonal matrix using the divide and conquer method. More...
 
magma_int_t magma_cungtr (magma_uplo_t uplo, magma_int_t n, magmaFloatComplex *A, magma_int_t lda, magmaFloatComplex *tau, magmaFloatComplex *work, magma_int_t lwork, magmaFloatComplex *dT, magma_int_t nb, magma_int_t *info)
 CUNGTR generates a complex unitary matrix Q which is defined as the product of n-1 elementary reflectors of order N, as returned by CHETRD: More...
 
magma_int_t magma_cunmtr (magma_side_t side, magma_uplo_t uplo, magma_trans_t trans, magma_int_t m, magma_int_t n, magmaFloatComplex *A, magma_int_t lda, magmaFloatComplex *tau, magmaFloatComplex *C, magma_int_t ldc, magmaFloatComplex *work, magma_int_t lwork, magma_int_t *info)
 CUNMTR overwrites the general complex M-by-N matrix C with. More...
 
magma_int_t magma_cunmtr_gpu (magma_side_t side, magma_uplo_t uplo, magma_trans_t trans, magma_int_t m, magma_int_t n, magmaFloatComplex *dA, magma_int_t ldda, magmaFloatComplex *tau, magmaFloatComplex *dC, magma_int_t lddc, magmaFloatComplex *wA, magma_int_t ldwa, magma_int_t *info)
 CUNMTR overwrites the general complex M-by-N matrix C with. More...
 
magma_int_t magma_cunmtr_m (magma_int_t nrgpu, magma_side_t side, magma_uplo_t uplo, magma_trans_t trans, magma_int_t m, magma_int_t n, magmaFloatComplex *A, magma_int_t lda, magmaFloatComplex *tau, magmaFloatComplex *C, magma_int_t ldc, magmaFloatComplex *work, magma_int_t lwork, magma_int_t *info)
 CUNMTR overwrites the general complex M-by-N matrix C with. More...
 

Detailed Description

Function Documentation

magma_int_t magma_chegst ( magma_int_t  itype,
magma_uplo_t  uplo,
magma_int_t  n,
magmaFloatComplex *  A,
magma_int_t  lda,
magmaFloatComplex *  B,
magma_int_t  ldb,
magma_int_t *  info 
)

CHEGST reduces a complex Hermitian-definite generalized eigenproblem to standard form.

If ITYPE = 1, the problem is A*x = lambda*B*x, and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)

If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H*A*L.

B must have been previously factorized as U**H*U or L*L**H by CPOTRF.

Parameters
[in]itypeINTEGER = 1: compute inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H); = 2 or 3: compute U*A*U**H or L**H*A*L.
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A is stored and B is factored as U**H*U;
  • = MagmaLower: Lower triangle of A is stored and B is factored as L*L**H.
[in]nINTEGER The order of the matrices A and B. N >= 0.
[in,out]ACOMPLEX array, dimension (LDA,N) On entry, the Hermitian matrix A. If UPLO = MagmaUpper, the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = MagmaLower, the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced.
On exit, if INFO = 0, the transformed matrix, stored in the same format as A.
[in]ldaINTEGER The leading dimension of the array A. LDA >= max(1,N).
[in]BCOMPLEX array, dimension (LDB,N) The triangular factor from the Cholesky factorization of B, as returned by CPOTRF.
[in]ldbINTEGER The leading dimension of the array B. LDB >= max(1,N).
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value
magma_int_t magma_chegst_gpu ( magma_int_t  itype,
magma_uplo_t  uplo,
magma_int_t  n,
magmaFloatComplex *  dA,
magma_int_t  ldda,
magmaFloatComplex *  dB,
magma_int_t  lddb,
magma_int_t *  info 
)

CHEGST_GPU reduces a complex Hermitian-definite generalized eigenproblem to standard form.

If ITYPE = 1, the problem is A*x = lambda*B*x, and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)

If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H*A*L.

B must have been previously factorized as U**H*U or L*L**H by CPOTRF.

Parameters
[in]itypeINTEGER = 1: compute inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H); = 2 or 3: compute U*A*U**H or L**H*A*L.
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A is stored and B is factored as U**H*U;
  • = MagmaLower: Lower triangle of A is stored and B is factored as L*L**H.
[in]nINTEGER The order of the matrices A and B. N >= 0.
[in,out]dACOMPLEX array, dimension (LDA,N) On entry, the Hermitian matrix A. If UPLO = MagmaUpper, the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = MagmaLower, the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced.
On exit, if INFO = 0, the transformed matrix, stored in the same format as A.
[in]lddaINTEGER The leading dimension of the array A. LDA >= max(1,N).
[in]dBCOMPLEX array, dimension (LDB,N) The triangular factor from the Cholesky factorization of B, as returned by CPOTRF.
[in]lddbINTEGER The leading dimension of the array B. LDB >= max(1,N).
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value
magma_int_t magma_chegst_m ( magma_int_t  nrgpu,
magma_int_t  itype,
magma_uplo_t  uplo,
magma_int_t  n,
magmaFloatComplex *  A,
magma_int_t  lda,
magmaFloatComplex *  B,
magma_int_t  ldb,
magma_int_t *  info 
)

CHEGST_M reduces a complex Hermitian-definite generalized eigenproblem to standard form.

If ITYPE = 1, the problem is A*x = lambda*B*x, and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)

If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H*A*L.

B must have been previously factorized as U**H*U or L*L**H by CPOTRF.

Parameters
[in]nrgpuINTEGER Number of GPUs to use.
[in]itypeINTEGER = 1: compute inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H); = 2 or 3: compute U*A*U**H or L**H*A*L.
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A is stored and B is factored as U**H*U;
  • = MagmaLower: Lower triangle of A is stored and B is factored as L*L**H.
[in]nINTEGER The order of the matrices A and B. N >= 0.
[in,out]ACOMPLEX array, dimension (LDA,N) On entry, the Hermitian matrix A. If UPLO = MagmaUpper, the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = MagmaLower, the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced.
On exit, if INFO = 0, the transformed matrix, stored in the same format as A.
[in]ldaINTEGER The leading dimension of the array A. LDA >= max(1,N).
[in]BCOMPLEX array, dimension (LDB,N) The triangular factor from the Cholesky factorization of B, as returned by CPOTRF.
[in]ldbINTEGER The leading dimension of the array B. LDB >= max(1,N).
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value
magma_int_t magma_chetrd ( magma_uplo_t  uplo,
magma_int_t  n,
magmaFloatComplex *  A,
magma_int_t  lda,
float *  d,
float *  e,
magmaFloatComplex *  tau,
magmaFloatComplex *  work,
magma_int_t  lwork,
magma_int_t *  info 
)

CHETRD reduces a complex Hermitian matrix A to real symmetric tridiagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T.

Parameters
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A is stored;
  • = MagmaLower: Lower triangle of A is stored.
[in]nINTEGER The order of the matrix A. N >= 0.
[in,out]ACOMPLEX array, dimension (LDA,N) On entry, the Hermitian matrix A. If UPLO = MagmaUpper, the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = MagmaLower, the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. On exit, if UPLO = MagmaUpper, the diagonal and first superdiagonal of A are overwritten by the corresponding elements of the tridiagonal matrix T, and the elements above the first superdiagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors; if UPLO = MagmaLower, the diagonal and first subdiagonal of A are over- written by the corresponding elements of the tridiagonal matrix T, and the elements below the first subdiagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. See Further Details.
[in]ldaINTEGER The leading dimension of the array A. LDA >= max(1,N).
[out]dCOMPLEX array, dimension (N) The diagonal elements of the tridiagonal matrix T: D(i) = A(i,i).
[out]eCOMPLEX array, dimension (N-1) The off-diagonal elements of the tridiagonal matrix T: E(i) = A(i,i+1) if UPLO = MagmaUpper, E(i) = A(i+1,i) if UPLO = MagmaLower.
[out]tauCOMPLEX array, dimension (N-1) The scalar factors of the elementary reflectors (see Further Details).
[out]work(workspace) COMPLEX array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
[in]lworkINTEGER The dimension of the array WORK. LWORK >= N*NB, where NB is the optimal blocksize given by magma_get_chetrd_nb().
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.
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

Further Details

If UPLO = MagmaUpper, the matrix Q is represented as a product of elementary reflectors

Q = H(n-1) . . . H(2) H(1).

Each H(i) has the form

H(i) = I - tau * v * v'

where tau is a complex scalar, and v is a complex vector with v(i+1:n) = 0 and v(i) = 1; v(1:i-1) is stored on exit in A(1:i-1,i+1), and tau in TAU(i).

If UPLO = MagmaLower, the matrix Q is represented as a product of elementary reflectors

Q = H(1) H(2) . . . H(n-1).

Each H(i) has the form

H(i) = I - tau * v * v'

where tau is a complex scalar, and v is a complex vector with v(1:i) = 0 and v(i+1) = 1; v(i+2:n) is stored on exit in A(i+2:n,i), and tau in TAU(i).

The contents of A on exit are illustrated by the following examples with n = 5:

if UPLO = MagmaUpper: if UPLO = MagmaLower:

( d e v2 v3 v4 ) ( d ) ( d e v3 v4 ) ( e d ) ( d e v4 ) ( v1 e d ) ( d e ) ( v1 v2 e d ) ( d ) ( v1 v2 v3 e d )

where d and e denote diagonal and off-diagonal elements of T, and vi denotes an element of the vector defining H(i).

magma_int_t magma_chetrd2_gpu ( magma_uplo_t  uplo,
magma_int_t  n,
magmaFloatComplex *  dA,
magma_int_t  ldda,
float *  d,
float *  e,
magmaFloatComplex *  tau,
magmaFloatComplex *  wA,
magma_int_t  ldwa,
magmaFloatComplex *  work,
magma_int_t  lwork,
magmaFloatComplex *  dwork,
magma_int_t  ldwork,
magma_int_t *  info 
)

CHETRD2_GPU reduces a complex Hermitian matrix A to real symmetric tridiagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T.

This version passes a workspace that is used in an optimized GPU matrix-vector product.

Parameters
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A is stored;
  • = MagmaLower: Lower triangle of A is stored.
[in]nINTEGER The order of the matrix A. N >= 0.
[in,out]dACOMPLEX array, dimension (LDA,N) On entry, the Hermitian matrix A. If UPLO = MagmaUpper, the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = MagmaLower, the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. On exit, if UPLO = MagmaUpper, the diagonal and first superdiagonal of A are overwritten by the corresponding elements of the tridiagonal matrix T, and the elements above the first superdiagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors; if UPLO = MagmaLower, the diagonal and first subdiagonal of A are over- written by the corresponding elements of the tridiagonal matrix T, and the elements below the first subdiagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. See Further Details.
[in]lddaINTEGER The leading dimension of the array A. LDA >= max(1,N).
[out]dCOMPLEX array, dimension (N) The diagonal elements of the tridiagonal matrix T: D(i) = A(i,i).
[out]eCOMPLEX array, dimension (N-1) The off-diagonal elements of the tridiagonal matrix T: E(i) = A(i,i+1) if UPLO = MagmaUpper, E(i) = A(i+1,i) if UPLO = MagmaLower.
[out]tauCOMPLEX array, dimension (N-1) The scalar factors of the elementary reflectors (see Further Details).
[out]wA(workspace) COMPLEX array, dimension (LDA,N) On exit the diagonal, the upper part (UPLO=MagmaUpper) or the lower part (UPLO=MagmaLower) are copies of DA
[in]ldwaINTEGER The leading dimension of the array wA. LDWA >= max(1,N).
[out]work(workspace) COMPLEX array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
[in]lworkINTEGER The dimension of the array WORK. LWORK >= 1. For optimum performance LWORK >= N*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.
[out]dwork(workspace) COMPLEX array on the GPU, dim (MAX(1,LDWORK))
[in]ldworkINTEGER The dimension of the array DWORK. LDWORK >= (n*n+64-1)/64 + 2*n*nb, where nb = magma_get_chetrd_nb(n)
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

Further Details

If UPLO = MagmaUpper, the matrix Q is represented as a product of elementary reflectors

Q = H(n-1) . . . H(2) H(1).

Each H(i) has the form

H(i) = I - tau * v * v'

where tau is a complex scalar, and v is a complex vector with v(i+1:n) = 0 and v(i) = 1; v(1:i-1) is stored on exit in A(1:i-1,i+1), and tau in TAU(i).

If UPLO = MagmaLower, the matrix Q is represented as a product of elementary reflectors

Q = H(1) H(2) . . . H(n-1).

Each H(i) has the form

H(i) = I - tau * v * v'

where tau is a complex scalar, and v is a complex vector with v(1:i) = 0 and v(i+1) = 1; v(i+2:n) is stored on exit in A(i+2:n,i), and tau in TAU(i).

The contents of A on exit are illustrated by the following examples with n = 5:

if UPLO = MagmaUpper: if UPLO = MagmaLower:

(  d   e   v2  v3  v4 )              (  d                  )
(      d   e   v3  v4 )              (  e   d              )
(          d   e   v4 )              (  v1  e   d          )
(              d   e  )              (  v1  v2  e   d      )
(                  d  )              (  v1  v2  v3  e   d  )

where d and e denote diagonal and off-diagonal elements of T, and vi denotes an element of the vector defining H(i).

magma_int_t magma_chetrd_gpu ( magma_uplo_t  uplo,
magma_int_t  n,
magmaFloatComplex *  dA,
magma_int_t  ldda,
float *  d,
float *  e,
magmaFloatComplex *  tau,
magmaFloatComplex *  wA,
magma_int_t  ldwa,
magmaFloatComplex *  work,
magma_int_t  lwork,
magma_int_t *  info 
)

CHETRD_GPU reduces a complex Hermitian matrix A to real symmetric tridiagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T.

Parameters
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A is stored;
  • = MagmaLower: Lower triangle of A is stored.
[in]nINTEGER The order of the matrix A. N >= 0.
[in,out]dACOMPLEX array on the GPU, dimension (LDA,N) On entry, the Hermitian matrix A. If UPLO = MagmaUpper, the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = MagmaLower, the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. On exit, if UPLO = MagmaUpper, the diagonal and first superdiagonal of A are overwritten by the corresponding elements of the tridiagonal matrix T, and the elements above the first superdiagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors; if UPLO = MagmaLower, the diagonal and first subdiagonal of A are over- written by the corresponding elements of the tridiagonal matrix T, and the elements below the first subdiagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. See Further Details.
[in]lddaINTEGER The leading dimension of the array A. LDA >= max(1,N).
[out]dCOMPLEX array, dimension (N) The diagonal elements of the tridiagonal matrix T: D(i) = A(i,i).
[out]eCOMPLEX array, dimension (N-1) The off-diagonal elements of the tridiagonal matrix T: E(i) = A(i,i+1) if UPLO = MagmaUpper, E(i) = A(i+1,i) if UPLO = MagmaLower.
[out]tauCOMPLEX array, dimension (N-1) The scalar factors of the elementary reflectors (see Further Details).
[out]wA(workspace) COMPLEX array, dimension (LDA,N) On exit the diagonal, the upper part (UPLO=MagmaUpper) or the lower part (UPLO=MagmaLower) are copies of DA
[in]ldwaINTEGER The leading dimension of the array wA. LDWA >= max(1,N).
[out]work(workspace) COMPLEX array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
[in]lworkINTEGER The dimension of the array WORK. LWORK >= N*NB, where NB is the optimal blocksize given by magma_get_chetrd_nb().
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.
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

Further Details

If UPLO = MagmaUpper, the matrix Q is represented as a product of elementary reflectors

Q = H(n-1) . . . H(2) H(1).

Each H(i) has the form

H(i) = I - tau * v * v'

where tau is a complex scalar, and v is a complex vector with v(i+1:n) = 0 and v(i) = 1; v(1:i-1) is stored on exit in A(1:i-1,i+1), and tau in TAU(i).

If UPLO = MagmaLower, the matrix Q is represented as a product of elementary reflectors

Q = H(1) H(2) . . . H(n-1).

Each H(i) has the form

H(i) = I - tau * v * v'

where tau is a complex scalar, and v is a complex vector with v(1:i) = 0 and v(i+1) = 1; v(i+2:n) is stored on exit in A(i+2:n,i), and tau in TAU(i).

The contents of A on exit are illustrated by the following examples with n = 5:

if UPLO = MagmaUpper: if UPLO = MagmaLower:

( d e v2 v3 v4 ) ( d ) ( d e v3 v4 ) ( e d ) ( d e v4 ) ( v1 e d ) ( d e ) ( v1 v2 e d ) ( d ) ( v1 v2 v3 e d )

where d and e denote diagonal and off-diagonal elements of T, and vi denotes an element of the vector defining H(i).

magma_int_t magma_chetrd_mgpu ( magma_int_t  num_gpus,
magma_int_t  k,
magma_uplo_t  uplo,
magma_int_t  n,
magmaFloatComplex *  A,
magma_int_t  lda,
float *  d,
float *  e,
magmaFloatComplex *  tau,
magmaFloatComplex *  work,
magma_int_t  lwork,
magma_int_t *  info 
)

CHETRD reduces a complex Hermitian matrix A to real symmetric tridiagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T.

Parameters
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A is stored;
  • = MagmaLower: Lower triangle of A is stored.
[in]nINTEGER The order of the matrix A. N >= 0.
[in,out]ACOMPLEX array, dimension (LDA,N) On entry, the Hermitian matrix A. If UPLO = MagmaUpper, the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = MagmaLower, the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. On exit, if UPLO = MagmaUpper, the diagonal and first superdiagonal of A are overwritten by the corresponding elements of the tridiagonal matrix T, and the elements above the first superdiagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors; if UPLO = MagmaLower, the diagonal and first subdiagonal of A are over- written by the corresponding elements of the tridiagonal matrix T, and the elements below the first subdiagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. See Further Details.
[in]ldaINTEGER The leading dimension of the array A. LDA >= max(1,N).
[out]dCOMPLEX array, dimension (N) The diagonal elements of the tridiagonal matrix T: D(i) = A(i,i).
[out]eCOMPLEX array, dimension (N-1) The off-diagonal elements of the tridiagonal matrix T: E(i) = A(i,i+1) if UPLO = MagmaUpper, E(i) = A(i+1,i) if UPLO = MagmaLower.
[out]tauCOMPLEX array, dimension (N-1) The scalar factors of the elementary reflectors (see Further Details).
[out]work(workspace) COMPLEX array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
[in]lworkINTEGER The dimension of the array WORK. LWORK >= 1. For optimum performance LWORK >= N*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.
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

Further Details

If UPLO = MagmaUpper, the matrix Q is represented as a product of elementary reflectors

Q = H(n-1) . . . H(2) H(1).

Each H(i) has the form

H(i) = I - tau * v * v'

where tau is a complex scalar, and v is a complex vector with v(i+1:n) = 0 and v(i) = 1; v(1:i-1) is stored on exit in A(1:i-1,i+1), and tau in TAU(i).

If UPLO = MagmaLower, the matrix Q is represented as a product of elementary reflectors

Q = H(1) H(2) . . . H(n-1).

Each H(i) has the form

H(i) = I - tau * v * v'

where tau is a complex scalar, and v is a complex vector with v(1:i) = 0 and v(i+1) = 1; v(i+2:n) is stored on exit in A(i+2:n,i), and tau in TAU(i).

The contents of A on exit are illustrated by the following examples with n = 5:

if UPLO = MagmaUpper: if UPLO = MagmaLower:

( d e v2 v3 v4 ) ( d ) ( d e v3 v4 ) ( e d ) ( d e v4 ) ( v1 e d ) ( d e ) ( v1 v2 e d ) ( d ) ( v1 v2 v3 e d )

where d and e denote diagonal and off-diagonal elements of T, and vi denotes an element of the vector defining H(i).

magma_int_t magma_cstedx ( magma_range_t  range,
magma_int_t  n,
float  vl,
float  vu,
magma_int_t  il,
magma_int_t  iu,
float *  d,
float *  e,
magmaFloatComplex *  Z,
magma_int_t  ldz,
float *  rwork,
magma_int_t  lrwork,
magma_int_t *  iwork,
magma_int_t  liwork,
float *  dwork,
magma_int_t *  info 
)

CSTEDX computes some eigenvalues and eigenvectors of a symmetric tridiagonal matrix using the divide and conquer method.

This code makes very mild assumptions about floating point arithmetic. It will work on machines with a guard digit in add/subtract, or on those binary machines without guard digits which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or Cray-2. It could conceivably fail on hexadecimal or decimal machines without guard digits, but we know of none. See SLAEX3 for details.

Parameters
[in]rangemagma_range_t
  • = MagmaRangeAll: all eigenvalues will be found.
  • = MagmaRangeV: all eigenvalues in the half-open interval (VL,VU] will be found.
  • = MagmaRangeI: the IL-th through IU-th eigenvalues will be found.
[in]nINTEGER The dimension of the symmetric tridiagonal matrix. N >= 0.
[in]vlREAL
[in]vuREAL If RANGE=MagmaRangeV, the lower and upper bounds of the interval to be searched for eigenvalues. VL < VU. Not referenced if RANGE = MagmaRangeAll or MagmaRangeI.
[in]ilINTEGER
[in]iuINTEGER If RANGE=MagmaRangeI, the indices (in ascending order) of the smallest and largest eigenvalues to be returned. 1 <= IL <= IU <= N, if N > 0; IL = 1 and IU = 0 if N = 0. Not referenced if RANGE = MagmaRangeAll or MagmaRangeV.
[in,out]dREAL array, dimension (N) On entry, the diagonal elements of the tridiagonal matrix. On exit, if INFO = 0, the eigenvalues in ascending order.
[in,out]eREAL array, dimension (N-1) On entry, the subdiagonal elements of the tridiagonal matrix. On exit, E has been destroyed.
[out]ZCOMPLEX array, dimension (LDZ,N) On exit, if INFO = 0, Z contains the orthonormal eigenvectors of the symmetric tridiagonal matrix.
[in]ldzINTEGER The leading dimension of the array Z. LDZ >= max(1,N).
[out]rwork(workspace) REAL array, dimension (LRWORK) On exit, if INFO = 0, RWORK(1) returns the optimal LRWORK.
[in]lrworkINTEGER The dimension of the array RWORK. LRWORK >= 1 + 4*N + 2*N**2. Note that if N is less than or equal to the minimum divide size, usually 25, then LRWORK need only be max(1,2*(N-1)).
If LRWORK = -1, then a workspace query is assumed; the routine only calculates the optimal sizes of the WORK, RWORK and IWORK arrays, returns these values as the first entries of the WORK, RWORK and IWORK arrays, and no error message related to LWORK or LRWORK or LIWORK is issued by XERBLA.
[out]iwork(workspace) INTEGER array, dimension (MAX(1,LIWORK)) On exit, if INFO = 0, IWORK(1) returns the optimal LIWORK.
[in]liworkINTEGER The dimension of the array IWORK. LIWORK >= 3 + 5*N . Note that if N is less than or equal to the minimum divide size, usually 25, then LIWORK need only be 1.
If LIWORK = -1, then a workspace query is assumed; the routine only calculates the optimal sizes of the WORK, RWORK and IWORK arrays, returns these values as the first entries of the WORK, RWORK and IWORK arrays, and no error message related to LWORK or LRWORK or LIWORK is issued by XERBLA.
dwork(workspace) REAL array, dimension (3*N*N/2+3*N)
[out]infoINTEGER
  • = 0: successful exit.
  • < 0: if INFO = -i, the i-th argument had an illegal value.
  • > 0: The algorithm failed to compute an eigenvalue while working on the submatrix lying in rows and columns INFO/(N+1) through mod(INFO,N+1).

Further Details

Based on contributions by Jeff Rutter, Computer Science Division, University of California at Berkeley, USA

magma_int_t magma_cstedx_m ( magma_int_t  nrgpu,
magma_range_t  range,
magma_int_t  n,
float  vl,
float  vu,
magma_int_t  il,
magma_int_t  iu,
float *  d,
float *  e,
magmaFloatComplex *  Z,
magma_int_t  ldz,
float *  rwork,
magma_int_t  lrwork,
magma_int_t *  iwork,
magma_int_t  liwork,
magma_int_t *  info 
)

CSTEDX computes some eigenvalues and eigenvectors of a symmetric tridiagonal matrix using the divide and conquer method.

This code makes very mild assumptions about floating point arithmetic. It will work on machines with a guard digit in add/subtract, or on those binary machines without guard digits which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or Cray-2. It could conceivably fail on hexadecimal or decimal machines without guard digits, but we know of none. See SLAEX3 for details.

Parameters
[in]nrgpuINTEGER Number of GPUs to use.
[in]rangemagma_range_t
  • = MagmaRangeAll: all eigenvalues will be found.
  • = MagmaRangeV: all eigenvalues in the half-open interval (VL,VU] will be found.
  • = MagmaRangeI: the IL-th through IU-th eigenvalues will be found.
[in]nINTEGER The dimension of the symmetric tridiagonal matrix. N >= 0.
[in]vlREAL
[in]vuREAL If RANGE=MagmaRangeV, the lower and upper bounds of the interval to be searched for eigenvalues. VL < VU. Not referenced if RANGE = MagmaRangeAll or MagmaRangeI.
[in]ilINTEGER
[in]iuINTEGER If RANGE=MagmaRangeI, the indices (in ascending order) of the smallest and largest eigenvalues to be returned. 1 <= IL <= IU <= N, if N > 0; IL = 1 and IU = 0 if N = 0. Not referenced if RANGE = MagmaRangeAll or MagmaRangeV.
[in,out]dREAL array, dimension (N) On entry, the diagonal elements of the tridiagonal matrix. On exit, if INFO = 0, the eigenvalues in ascending order.
[in,out]eREAL array, dimension (N-1) On entry, the subdiagonal elements of the tridiagonal matrix. On exit, E has been destroyed.
[out]ZCOMPLEX array, dimension (LDZ,N) On exit, if INFO = 0, Z contains the orthonormal eigenvectors of the symmetric tridiagonal matrix.
[in]ldzINTEGER The leading dimension of the array Z. LDZ >= max(1,N).
[out]rwork(workspace) REAL array, dimension (LRWORK) On exit, if INFO = 0, RWORK(1) returns the optimal LRWORK.
[in]lrworkINTEGER The dimension of the array RWORK. LRWORK >= 1 + 4*N + 2*N**2 . Note that if N is less than or equal to the minimum divide size, usually 25, then LRWORK need only be max(1,2*(N-1)).
If LRWORK = -1, then a workspace query is assumed; the routine only calculates the optimal sizes of the WORK, RWORK and IWORK arrays, returns these values as the first entries of the WORK, RWORK and IWORK arrays, and no error message related to LWORK or LRWORK or LIWORK is issued by XERBLA.
[out]iwork(workspace) INTEGER array, dimension (MAX(1,LIWORK)) On exit, if INFO = 0, IWORK(1) returns the optimal LIWORK.
[in]liworkINTEGER The dimension of the array IWORK. LIWORK >= 3 + 5*N . Note that if N is less than or equal to the minimum divide size, usually 25, then LIWORK need only be 1.
If LIWORK = -1, then a workspace query is assumed; the routine only calculates the optimal sizes of the WORK, RWORK and IWORK arrays, returns these values as the first entries of the WORK, RWORK and IWORK arrays, and no error message related to LWORK or LRWORK or LIWORK is issued by XERBLA.
[out]infoINTEGER
  • = 0: successful exit.
  • < 0: if INFO = -i, the i-th argument had an illegal value.
  • > 0: The algorithm failed to compute an eigenvalue while working on the submatrix lying in rows and columns INFO/(N+1) through mod(INFO,N+1).

Further Details

Based on contributions by Jeff Rutter, Computer Science Division, University of California at Berkeley, USA

magma_int_t magma_cungtr ( magma_uplo_t  uplo,
magma_int_t  n,
magmaFloatComplex *  A,
magma_int_t  lda,
magmaFloatComplex *  tau,
magmaFloatComplex *  work,
magma_int_t  lwork,
magmaFloatComplex *  dT,
magma_int_t  nb,
magma_int_t *  info 
)

CUNGTR generates a complex unitary matrix Q which is defined as the product of n-1 elementary reflectors of order N, as returned by CHETRD:

if UPLO = MagmaUpper, Q = H(n-1) . . . H(2) H(1),

if UPLO = MagmaLower, Q = H(1) H(2) . . . H(n-1).

Parameters
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A contains elementary reflectors from CHETRD;
  • = MagmaLower: Lower triangle of A contains elementary reflectors from CHETRD.
[in]nINTEGER The order of the matrix Q. N >= 0.
[in,out]ACOMPLEX array, dimension (LDA,N) On entry, the vectors which define the elementary reflectors, as returned by CHETRD. On exit, the N-by-N unitary matrix Q.
[in]ldaINTEGER The leading dimension of the array A. LDA >= N.
[in]tauCOMPLEX array, dimension (N-1) TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by CHETRD.
[out]work(workspace) COMPLEX array, dimension (LWORK) On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
[in]lworkINTEGER The dimension of the array WORK. LWORK >= N-1. For optimum performance LWORK >= N*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.
[in]dTCOMPLEX array on the GPU device. DT contains the T matrices used in blocking the elementary reflectors H(i) as returned by magma_chetrd.
[in]nbINTEGER This is the block size used in CHETRD, and correspondingly the size of the T matrices, used in the factorization, and stored in DT.
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value
magma_int_t magma_cunmtr ( magma_side_t  side,
magma_uplo_t  uplo,
magma_trans_t  trans,
magma_int_t  m,
magma_int_t  n,
magmaFloatComplex *  A,
magma_int_t  lda,
magmaFloatComplex *  tau,
magmaFloatComplex *  C,
magma_int_t  ldc,
magmaFloatComplex *  work,
magma_int_t  lwork,
magma_int_t *  info 
)

CUNMTR overwrites the general complex M-by-N matrix C with.

            SIDE = MagmaLeft     SIDE = MagmaRight

TRANS = MagmaNoTrans: Q * C C * Q TRANS = MagmaTrans: Q**H * C C * Q**H

where Q is a complex unitary matrix of order nq, with nq = m if SIDE = MagmaLeft and nq = n if SIDE = MagmaRight. Q is defined as the product of nq-1 elementary reflectors, as returned by SSYTRD:

if UPLO = MagmaUpper, Q = H(nq-1) . . . H(2) H(1);

if UPLO = MagmaLower, Q = H(1) H(2) . . . H(nq-1).

Parameters
[in]sidemagma_side_t
  • = MagmaLeft: apply Q or Q**H from the Left;
  • = MagmaRight: apply Q or Q**H from the Right.
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A contains elementary reflectors from SSYTRD;
  • = MagmaLower: Lower triangle of A contains elementary reflectors from SSYTRD.
[in]transmagma_trans_t
  • = MagmaNoTrans: No transpose, apply Q;
  • = MagmaTrans: Transpose, apply Q**H.
[in]mINTEGER The number of rows of the matrix C. M >= 0.
[in]nINTEGER The number of columns of the matrix C. N >= 0.
[in]ACOMPLEX array, dimension (LDA,M) if SIDE = MagmaLeft (LDA,N) if SIDE = MagmaRight The vectors which define the elementary reflectors, as returned by SSYTRD.
[in]ldaINTEGER The leading dimension of the array A. LDA >= max(1,M) if SIDE = MagmaLeft; LDA >= max(1,N) if SIDE = MagmaRight.
[in]tauCOMPLEX array, dimension (M-1) if SIDE = MagmaLeft (N-1) if SIDE = MagmaRight TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by SSYTRD.
[in,out]CCOMPLEX array, dimension (LDC,N) On entry, the M-by-N matrix C. On exit, C is overwritten by Q*C or Q**H * C or C * Q**H or C*Q.
[in]ldcINTEGER The leading dimension of the array C. LDC >= max(1,M).
[out]work(workspace) COMPLEX array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
[in]lworkINTEGER The dimension of the array WORK. If SIDE = MagmaLeft, LWORK >= max(1,N); if SIDE = MagmaRight, LWORK >= max(1,M). For optimum performance LWORK >= N*NB if SIDE = MagmaLeft, and LWORK >= M*NB if SIDE = MagmaRight, 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.
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value
magma_int_t magma_cunmtr_gpu ( magma_side_t  side,
magma_uplo_t  uplo,
magma_trans_t  trans,
magma_int_t  m,
magma_int_t  n,
magmaFloatComplex *  dA,
magma_int_t  ldda,
magmaFloatComplex *  tau,
magmaFloatComplex *  dC,
magma_int_t  lddc,
magmaFloatComplex *  wA,
magma_int_t  ldwa,
magma_int_t *  info 
)

CUNMTR overwrites the general complex M-by-N matrix C with.

            SIDE = MagmaLeft     SIDE = MagmaRight

TRANS = MagmaNoTrans: Q * C C * Q TRANS = MagmaTrans: Q**H * C C * Q**H

where Q is a complex unitary matrix of order nq, with nq = m if SIDE = MagmaLeft and nq = n if SIDE = MagmaRight. Q is defined as the product of nq-1 elementary reflectors, as returned by CHETRD:

if UPLO = MagmaUpper, Q = H(nq-1) . . . H(2) H(1);

if UPLO = MagmaLower, Q = H(1) H(2) . . . H(nq-1).

Parameters
[in]sidemagma_side_t
  • = MagmaLeft: apply Q or Q**H from the Left;
  • = MagmaRight: apply Q or Q**H from the Right.
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A contains elementary reflectors from CHETRD;
  • = MagmaLower: Lower triangle of A contains elementary reflectors from CHETRD.
[in]transmagma_trans_t
  • = MagmaNoTrans: No transpose, apply Q;
  • = MagmaTrans: Transpose, apply Q**H.
[in]mINTEGER The number of rows of the matrix C. M >= 0.
[in]nINTEGER The number of columns of the matrix C. N >= 0.
[in]dACOMPLEX array, dimension (LDDA,M) if SIDE = MagmaLeft (LDDA,N) if SIDE = MagmaRight The vectors which define the elementary reflectors, as returned by CHETRD_GPU. On output the diagonal, the subdiagonal and the upper part (UPLO=MagmaLower) or lower part (UPLO=MagmaUpper) are destroyed.
[in]lddaINTEGER The leading dimension of the array DA. LDDA >= max(1,M) if SIDE = MagmaLeft; LDDA >= max(1,N) if SIDE = MagmaRight.
[in]tauCOMPLEX array, dimension (M-1) if SIDE = MagmaLeft (N-1) if SIDE = MagmaRight TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by CHETRD.
[in,out]dCCOMPLEX array, dimension (LDDC,N) On entry, the M-by-N matrix C. On exit, C is overwritten by (Q*C) or (Q**H * C) or (C * Q**H) or (C*Q).
[in]lddcINTEGER The leading dimension of the array C. LDDC >= max(1,M).
[in]wA(workspace) COMPLEX array, dimension (LDWA,M) if SIDE = MagmaLeft (LDWA,N) if SIDE = MagmaRight The vectors which define the elementary reflectors, as returned by CHETRD_GPU.
[in]ldwaINTEGER The leading dimension of the array wA. LDWA >= max(1,M) if SIDE = MagmaLeft; LDWA >= max(1,N) if SIDE = MagmaRight.
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value
magma_int_t magma_cunmtr_m ( magma_int_t  nrgpu,
magma_side_t  side,
magma_uplo_t  uplo,
magma_trans_t  trans,
magma_int_t  m,
magma_int_t  n,
magmaFloatComplex *  A,
magma_int_t  lda,
magmaFloatComplex *  tau,
magmaFloatComplex *  C,
magma_int_t  ldc,
magmaFloatComplex *  work,
magma_int_t  lwork,
magma_int_t *  info 
)

CUNMTR overwrites the general complex M-by-N matrix C with.

            SIDE = MagmaLeft     SIDE = MagmaRight

TRANS = MagmaNoTrans: Q * C C * Q TRANS = MagmaTrans: Q**H * C C * Q**H

where Q is a complex unitary matrix of order nq, with nq = m if SIDE = MagmaLeft and nq = n if SIDE = MagmaRight. Q is defined as the product of nq-1 elementary reflectors, as returned by SSYTRD:

if UPLO = MagmaUpper, Q = H(nq-1) . . . H(2) H(1);

if UPLO = MagmaLower, Q = H(1) H(2) . . . H(nq-1).

Parameters
[in]nrgpuINTEGER Number of GPUs to use.
[in]sidemagma_side_t
  • = MagmaLeft: apply Q or Q**H from the Left;
  • = MagmaRight: apply Q or Q**H from the Right.
[in]uplomagma_uplo_t
  • = MagmaUpper: Upper triangle of A contains elementary reflectors from SSYTRD;
  • = MagmaLower: Lower triangle of A contains elementary reflectors from SSYTRD.
[in]transmagma_trans_t
  • = MagmaNoTrans: No transpose, apply Q;
  • = MagmaTrans: Transpose, apply Q**H.
[in]mINTEGER The number of rows of the matrix C. M >= 0.
[in]nINTEGER The number of columns of the matrix C. N >= 0.
[in]ACOMPLEX array, dimension (LDA,M) if SIDE = MagmaLeft (LDA,N) if SIDE = MagmaRight The vectors which define the elementary reflectors, as returned by SSYTRD.
[in]ldaINTEGER The leading dimension of the array A. LDA >= max(1,M) if SIDE = MagmaLeft; LDA >= max(1,N) if SIDE = MagmaRight.
[in]tauCOMPLEX array, dimension (M-1) if SIDE = MagmaLeft (N-1) if SIDE = MagmaRight TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by SSYTRD.
[in,out]CCOMPLEX array, dimension (LDC,N) On entry, the M-by-N matrix C. On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.
[in]ldcINTEGER The leading dimension of the array C. LDC >= max(1,M).
[out]work(workspace) COMPLEX array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
[in]lworkINTEGER The dimension of the array WORK. If SIDE = MagmaLeft, LWORK >= max(1,N); if SIDE = MagmaRight, LWORK >= max(1,M). For optimum performance LWORK >= N*NB if SIDE = MagmaLeft, and LWORK >= M*NB if SIDE = MagmaRight, 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.
[out]infoINTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value