MAGMA  2.3.0 Matrix Algebra for GPU and Multicore Architectures
sy2sb: 1st stage, full to band

## Functions

magma_int_t magma_dsytrd_sy2sb (magma_uplo_t uplo, magma_int_t n, magma_int_t nb, double *A, magma_int_t lda, double *tau, double *work, magma_int_t lwork, magmaDouble_ptr dT, magma_int_t *info)
DSYTRD_HE2HB reduces a real symmetric matrix A to real symmetric band-diagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T. More...

magma_int_t magma_dsytrd_sy2sb_mgpu (magma_uplo_t uplo, magma_int_t n, magma_int_t nb, double *A, magma_int_t lda, double *tau, double *work, magma_int_t lwork, magmaDouble_ptr dAmgpu[], magma_int_t ldda, magmaDouble_ptr dTmgpu[], magma_int_t lddt, magma_int_t ngpu, magma_int_t distblk, magma_queue_t queues[][20], magma_int_t nqueue, magma_int_t *info)
DSYTRD_HE2HB reduces a real symmetric matrix A to real symmetric band-diagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T. More...

magma_int_t magma_ssytrd_sy2sb (magma_uplo_t uplo, magma_int_t n, magma_int_t nb, float *A, magma_int_t lda, float *tau, float *work, magma_int_t lwork, magmaFloat_ptr dT, magma_int_t *info)
SSYTRD_HE2HB reduces a real symmetric matrix A to real symmetric band-diagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T. More...

magma_int_t magma_ssytrd_sy2sb_mgpu (magma_uplo_t uplo, magma_int_t n, magma_int_t nb, float *A, magma_int_t lda, float *tau, float *work, magma_int_t lwork, magmaFloat_ptr dAmgpu[], magma_int_t ldda, magmaFloat_ptr dTmgpu[], magma_int_t lddt, magma_int_t ngpu, magma_int_t distblk, magma_queue_t queues[][20], magma_int_t nqueue, magma_int_t *info)
SSYTRD_HE2HB reduces a real symmetric matrix A to real symmetric band-diagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T. More...

## Function Documentation

 magma_int_t magma_dsytrd_sy2sb ( magma_uplo_t uplo, magma_int_t n, magma_int_t nb, double * A, magma_int_t lda, double * tau, double * work, magma_int_t lwork, magmaDouble_ptr dT, magma_int_t * info )

DSYTRD_HE2HB reduces a real symmetric matrix A to real symmetric band-diagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T.

This version stores the triangular matrices T used in the accumulated Householder transformations (I - V T V').

Parameters
 [in] uplo magma_uplo_t = MagmaUpper: Upper triangle of A is stored; = MagmaLower: Lower triangle of A is stored. [in] n INTEGER The order of the matrix A. n >= 0. [in] nb INTEGER The inner blocking. nb >= 0. [in,out] A DOUBLE PRECISION array, dimension (LDA,N) On entry, the symmetric 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 Upper band-diagonal of A is overwritten by the corresponding elements of the band-diagonal matrix T, and the elements above the band diagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors; if UPLO = MagmaLower, the the Lower band-diagonal of A is overwritten by the corresponding elements of the band-diagonal matrix T, and the elements below the band-diagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. See Further Details. [in] lda INTEGER The leading dimension of the array A. LDA >= max(1,N). [out] tau DOUBLE PRECISION array, dimension (N-1) The scalar factors of the elementary reflectors (see Further Details). [out] work (workspace) DOUBLE PRECISION array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK[0] returns the optimal LWORK. [in] lwork INTEGER 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] dT DOUBLE PRECISION array on the GPU, dimension N*NB, where NB is the optimal blocksize. On exit dT holds the upper triangular matrices T from the accumulated Householder transformations (I - V T V') used in the factorization. The nb x nb matrices T are ordered consecutively in memory one after another. [out] info INTEGER = 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 real scalar, and v is a real 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 real scalar, and v is a real 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_dsytrd_sy2sb_mgpu ( magma_uplo_t uplo, magma_int_t n, magma_int_t nb, double * A, magma_int_t lda, double * tau, double * work, magma_int_t lwork, magmaDouble_ptr dAmgpu[], magma_int_t ldda, magmaDouble_ptr dTmgpu[], magma_int_t lddt, magma_int_t ngpu, magma_int_t distblk, magma_queue_t queues[][20], magma_int_t nqueue, magma_int_t * info )

DSYTRD_HE2HB reduces a real symmetric matrix A to real symmetric band-diagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T.

This version stores the triangular matrices T used in the accumulated Householder transformations (I - V T V').

Parameters
 [in] uplo magma_uplo_t = MagmaUpper: Upper triangle of A is stored; = MagmaLower: Lower triangle of A is stored. [in] n INTEGER The order of the matrix A. N >= 0. [in] nb INTEGER The inner blocking. nb >= 0. [in,out] A DOUBLE PRECISION array, dimension (LDA,N) On entry, the symmetric 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 Upper band-diagonal of A is overwritten by the corresponding elements of the band-diagonal matrix T, and the elements above the band diagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors; if UPLO = MagmaLower, the the Lower band-diagonal of A is overwritten by the corresponding elements of the band-diagonal matrix T, and the elements below the band-diagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. See Further Details. [in] lda INTEGER The leading dimension of the array A. LDA >= max(1,N). [out] tau DOUBLE PRECISION array, dimension (N-1) The scalar factors of the elementary reflectors (see Further Details). [out] work (workspace) DOUBLE PRECISION array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK[0] returns the optimal LWORK. [in] lwork INTEGER 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. [in,out] dAmgpu DOUBLE PRECISION array of pointer, dimension (ngpu) Each point to a DOUBLE PRECISION array, dimension (LDDA, nlocal) which hold the local matrix on each GPU. [in] ldda INTEGER The leading dimension of the array dAmgpu. ldda >= max(1,n). [in,out] dTmgpu DOUBLE PRECISION array of pointer, dimension (ngpu) Each point to a DOUBLE PRECISION array on the GPU, dimension n*nb, where nb is the optimal blocksize. On exit dT holds the upper triangular matrices T from the accumulated Householder transformations (I - V T V') used in the factorization. The nb x nb matrices T are ordered consecutively in memory one after another. [in] lddt INTEGER The leading dimension of each array dT. lddt >= max(1,nb). [in] ngpu INTEGER The number of GPUs. [in] distblk INTEGER Internal parameter for performance tuning. The size of the distribution/computation. [in] queues Array of magma_queue_t that point to the queues to be used in execution/communications. Dimension >= max(3, ngpu+1) Queue to execute in. [in] nqueue INTEGER The number of queues should be >= max(3, ngpu+1). [out] info INTEGER = 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 real scalar, and v is a real 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 real scalar, and v is a real 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_ssytrd_sy2sb ( magma_uplo_t uplo, magma_int_t n, magma_int_t nb, float * A, magma_int_t lda, float * tau, float * work, magma_int_t lwork, magmaFloat_ptr dT, magma_int_t * info )

SSYTRD_HE2HB reduces a real symmetric matrix A to real symmetric band-diagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T.

This version stores the triangular matrices T used in the accumulated Householder transformations (I - V T V').

Parameters
 [in] uplo magma_uplo_t = MagmaUpper: Upper triangle of A is stored; = MagmaLower: Lower triangle of A is stored. [in] n INTEGER The order of the matrix A. n >= 0. [in] nb INTEGER The inner blocking. nb >= 0. [in,out] A REAL array, dimension (LDA,N) On entry, the symmetric 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 Upper band-diagonal of A is overwritten by the corresponding elements of the band-diagonal matrix T, and the elements above the band diagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors; if UPLO = MagmaLower, the the Lower band-diagonal of A is overwritten by the corresponding elements of the band-diagonal matrix T, and the elements below the band-diagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. See Further Details. [in] lda INTEGER The leading dimension of the array A. LDA >= max(1,N). [out] tau REAL array, dimension (N-1) The scalar factors of the elementary reflectors (see Further Details). [out] work (workspace) REAL array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK[0] returns the optimal LWORK. [in] lwork INTEGER 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] dT REAL array on the GPU, dimension N*NB, where NB is the optimal blocksize. On exit dT holds the upper triangular matrices T from the accumulated Householder transformations (I - V T V') used in the factorization. The nb x nb matrices T are ordered consecutively in memory one after another. [out] info INTEGER = 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 real scalar, and v is a real 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 real scalar, and v is a real 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_ssytrd_sy2sb_mgpu ( magma_uplo_t uplo, magma_int_t n, magma_int_t nb, float * A, magma_int_t lda, float * tau, float * work, magma_int_t lwork, magmaFloat_ptr dAmgpu[], magma_int_t ldda, magmaFloat_ptr dTmgpu[], magma_int_t lddt, magma_int_t ngpu, magma_int_t distblk, magma_queue_t queues[][20], magma_int_t nqueue, magma_int_t * info )

SSYTRD_HE2HB reduces a real symmetric matrix A to real symmetric band-diagonal form T by an orthogonal similarity transformation: Q**H * A * Q = T.

This version stores the triangular matrices T used in the accumulated Householder transformations (I - V T V').

Parameters
 [in] uplo magma_uplo_t = MagmaUpper: Upper triangle of A is stored; = MagmaLower: Lower triangle of A is stored. [in] n INTEGER The order of the matrix A. N >= 0. [in] nb INTEGER The inner blocking. nb >= 0. [in,out] A REAL array, dimension (LDA,N) On entry, the symmetric 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 Upper band-diagonal of A is overwritten by the corresponding elements of the band-diagonal matrix T, and the elements above the band diagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors; if UPLO = MagmaLower, the the Lower band-diagonal of A is overwritten by the corresponding elements of the band-diagonal matrix T, and the elements below the band-diagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. See Further Details. [in] lda INTEGER The leading dimension of the array A. LDA >= max(1,N). [out] tau REAL array, dimension (N-1) The scalar factors of the elementary reflectors (see Further Details). [out] work (workspace) REAL array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK[0] returns the optimal LWORK. [in] lwork INTEGER 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. [in,out] dAmgpu REAL array of pointer, dimension (ngpu) Each point to a REAL array, dimension (LDDA, nlocal) which hold the local matrix on each GPU. [in] ldda INTEGER The leading dimension of the array dAmgpu. ldda >= max(1,n). [in,out] dTmgpu REAL array of pointer, dimension (ngpu) Each point to a REAL array on the GPU, dimension n*nb, where nb is the optimal blocksize. On exit dT holds the upper triangular matrices T from the accumulated Householder transformations (I - V T V') used in the factorization. The nb x nb matrices T are ordered consecutively in memory one after another. [in] lddt INTEGER The leading dimension of each array dT. lddt >= max(1,nb). [in] ngpu INTEGER The number of GPUs. [in] distblk INTEGER Internal parameter for performance tuning. The size of the distribution/computation. [in] queues Array of magma_queue_t that point to the queues to be used in execution/communications. Dimension >= max(3, ngpu+1) Queue to execute in. [in] nqueue INTEGER The number of queues should be >= max(3, ngpu+1). [out] info INTEGER = 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 real scalar, and v is a real 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 real scalar, and v is a real 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).