extern "C" magma_int_t
magma_sgehrd(magma_int_t n, magma_int_t ilo, magma_int_t ihi,
float *a, magma_int_t lda,
float *tau,
float *work, magma_int_t lwork,
float *dT,
magma_int_t *info)
{
/* -- MAGMA (version 1.3.0) --
Univ. of Tennessee, Knoxville
Univ. of California, Berkeley
Univ. of Colorado, Denver
November 2012
Purpose
=======
SGEHRD reduces a REAL general matrix A to upper Hessenberg form H by
an orthogonal similarity transformation: Q' * A * Q = H . This version
stores the triangular matrices used in the factorization so that they can
be applied directly (i.e., without being recomputed) later. As a result,
the application of Q is much faster.
Arguments
=========
N (input) INTEGER
The order of the matrix A. N >= 0.
ILO (input) INTEGER
IHI (input) INTEGER
It is assumed that A is already upper triangular in rows
and columns 1:ILO-1 and IHI+1:N. ILO and IHI are normally
set by a previous call to SGEBAL; otherwise they should be
set to 1 and N respectively. See Further Details.
1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
A (input/output) REAL array, dimension (LDA,N)
On entry, the N-by-N general matrix to be reduced.
On exit, the upper triangle and the first subdiagonal of A
are overwritten with the upper Hessenberg matrix H, 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.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
TAU (output) REAL array, dimension (N-1)
The scalar factors of the elementary reflectors (see Further
Details). Elements 1:ILO-1 and IHI:N-1 of TAU are set to
zero.
WORK (workspace/output) REAL array, dimension (LWORK)
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
LWORK (input) INTEGER
The length of the array WORK. LWORK >= max(1,N).
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.
dT (output) REAL array on the GPU, dimension N*NB,
where NB is the optimal blocksize. It stores the NB*NB blocks
of the triangular T matrices, used the the reduction.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value.
Further Details
===============
The matrix Q is represented as a product of (ihi-ilo) elementary
reflectors
Q = H(ilo) H(ilo+1) . . . H(ihi-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, v(i+1) = 1 and v(ihi+1:n) = 0; v(i+2:ihi) is stored on
exit in A(i+2:ihi,i), and tau in TAU(i).
The contents of A are illustrated by the following example, with
n = 7, ilo = 2 and ihi = 6:
on entry, on exit,
( a a a a a a a ) ( a a h h h h a )
( a a a a a a ) ( a h h h h a )
( a a a a a a ) ( h h h h h h )
( a a a a a a ) ( v2 h h h h h )
( a a a a a a ) ( v2 v3 h h h h )
( a a a a a a ) ( v2 v3 v4 h h h )
( a ) ( a )
where a denotes an element of the original matrix A, h denotes a
modified element of the upper Hessenberg matrix H, and vi denotes an
element of the vector defining H(i).
This implementation follows the hybrid algorithm and notations described in
S. Tomov and J. Dongarra, "Accelerating the reduction to upper Hessenberg
form through hybrid GPU-based computing," University of Tennessee Computer
Science Technical Report, UT-CS-09-642 (also LAPACK Working Note 219),
May 24, 2009.
===================================================================== */
float c_one = MAGMA_S_ONE;
float c_zero = MAGMA_S_ZERO;
magma_int_t nb = magma_get_sgehrd_nb(n);
magma_int_t N = n, ldda = n;
magma_int_t ib;
magma_int_t nh, iws;
magma_int_t nbmin, iinfo;
magma_int_t ldwork;
magma_int_t lquery;
--tau;
*info = 0;
MAGMA_S_SET2REAL( work[0], (float) n * nb );
lquery = lwork == -1;
if (n < 0) {
*info = -1;
} else if (ilo < 1 || ilo > max(1,n)) {
*info = -2;
} else if (ihi < min(ilo,n) || ihi > n) {
*info = -3;
} else if (lda < max(1,n)) {
*info = -5;
} else if (lwork < max(1,n) && ! lquery) {
*info = -8;
}
if (*info != 0) {
magma_xerbla( __func__, -(*info) );
return *info;
}
else if (lquery)
return *info;
/* Quick return if possible */
nh = ihi - ilo + 1;
if (nh <= 1) {
work[0] = c_one;
return *info;
}
float *da;
if (MAGMA_SUCCESS != magma_smalloc( &da, N*ldda + 2*N*nb + nb*nb )) {
*info = MAGMA_ERR_DEVICE_ALLOC;
return *info;
}
float *d_A = da;
float *d_work = da + (N+nb)*ldda;
magma_int_t i__;
float *t, *d_t;
magma_smalloc_cpu( &t, nb*nb );
if ( t == NULL ) {
magma_free( da );
*info = MAGMA_ERR_HOST_ALLOC;
return *info;
}
d_t = d_work + nb * ldda;
szero_nbxnb_block(nb, d_A+N*ldda, ldda);
/* Set elements 1:ILO-1 and IHI:N-1 of TAU to zero */
for (i__ = 1; i__ < ilo; ++i__)
tau[i__] = c_zero;
for (i__ = max(1,ihi); i__ < n; ++i__)
tau[i__] = c_zero;
for(i__=0; i__< nb*nb; i__+=4)
t[i__] = t[i__+1] = t[i__+2] = t[i__+3] = c_zero;
nbmin = 2;
iws = 1;
if (nb > 1 && nb < nh) {
/* Determine when to cross over from blocked to unblocked code
(last block is always handled by unblocked code) */
if (nb < nh) {
/* Determine if workspace is large enough for blocked code */
iws = n * nb;
if (lwork < iws) {
/* Not enough workspace to use optimal NB: determine the
minimum value of NB, and reduce NB or force use of
unblocked code */
nbmin = nb;
if (lwork >= n * nbmin)
nb = lwork / n;
else
nb = 1;
}
}
}
ldwork = n;
if (nb < nbmin || nb >= nh) {
/* Use unblocked code below */
i__ = ilo;
} else {
/* Use blocked code */
/* Copy the matrix to the GPU */
magma_ssetmatrix( N, N-ilo+1, a+(ilo-1)*(lda), lda, d_A, ldda );
for (i__ = ilo; i__ < ihi - nb; i__ += nb) {
/* Computing MIN */
ib = min(nb, ihi - i__);
/* Reduce columns i:i+ib-1 to Hessenberg form, returning the
matrices V and T of the block reflector H = I - V*T*V'
which performs the reduction, and also the matrix Y = A*V*T */
/* Get the current panel (no need for the 1st iteration) */
magma_sgetmatrix( ihi-i__+1, ib,
d_A + (i__ - ilo)*ldda + i__ - 1, ldda,
a + (i__ - 1 )*lda + i__ - 1, lda );
magma_slahr2(ihi, i__, ib,
d_A + (i__ - ilo)*ldda,
d_A + N*ldda + 1,
a + (i__ - 1 )*(lda) , lda,
&tau[i__], t, nb, work, ldwork);
/* Copy T from the CPU to D_T on the GPU */
d_t = dT + (i__ - ilo)*nb;
magma_ssetmatrix( nb, nb, t, nb, d_t, nb );
magma_slahru(n, ihi, i__ - 1, ib,
a + (i__ - 1 )*(lda), lda,
d_A + (i__ - ilo)*ldda,
d_A + (i__ - ilo)*ldda + i__ - 1,
d_A + N*ldda, d_t, d_work);
}
}
/* Use unblocked code to reduce the rest of the matrix */
if (!(nb < nbmin || nb >= nh))
magma_sgetmatrix( n, n-i__+1,
d_A+ (i__-ilo)*ldda, ldda,
a + (i__-1)*(lda), lda );
lapackf77_sgehd2(&n, &i__, &ihi, a, &lda, &tau[1], work, &iinfo);
MAGMA_S_SET2REAL( work[0], (float) iws );
magma_free( da );
magma_free_cpu(t);
return *info;
} /* magma_sgehrd */
extern "C" magma_int_t
magma_sgehrd(magma_int_t n, magma_int_t ilo, magma_int_t ihi,
float *A, magma_int_t lda,
float *tau,
float *work, magma_int_t lwork,
float *dT,
magma_int_t *info)
{
/* -- MAGMA (version 1.4.1) --
Univ. of Tennessee, Knoxville
Univ. of California, Berkeley
Univ. of Colorado, Denver
December 2013
Purpose
=======
SGEHRD reduces a REAL general matrix A to upper Hessenberg form H by
an orthogonal similarity transformation: Q' * A * Q = H . This version
stores the triangular matrices used in the factorization so that they can
be applied directly (i.e., without being recomputed) later. As a result,
the application of Q is much faster.
Arguments
=========
N (input) INTEGER
The order of the matrix A. N >= 0.
ILO (input) INTEGER
IHI (input) INTEGER
It is assumed that A is already upper triangular in rows
and columns 1:ILO-1 and IHI+1:N. ILO and IHI are normally
set by a previous call to SGEBAL; otherwise they should be
set to 1 and N respectively. See Further Details.
1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
A (input/output) REAL array, dimension (LDA,N)
On entry, the N-by-N general matrix to be reduced.
On exit, the upper triangle and the first subdiagonal of A
are overwritten with the upper Hessenberg matrix H, 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.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
TAU (output) REAL array, dimension (N-1)
The scalar factors of the elementary reflectors (see Further
Details). Elements 1:ILO-1 and IHI:N-1 of TAU are set to
zero.
WORK (workspace/output) REAL array, dimension (LWORK)
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
LWORK (input) INTEGER
The length of the array WORK. LWORK >= max(1,N).
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.
dT (output) REAL array on the GPU, dimension NB*N,
where NB is the optimal blocksize. It stores the NB*NB blocks
of the triangular T matrices used in the reduction.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value.
Further Details
===============
The matrix Q is represented as a product of (ihi-ilo) elementary
reflectors
Q = H(ilo) H(ilo+1) . . . H(ihi-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, v(i+1) = 1 and v(ihi+1:n) = 0; v(i+2:ihi) is stored on
exit in A(i+2:ihi,i), and tau in TAU(i).
The contents of A are illustrated by the following example, with
n = 7, ilo = 2 and ihi = 6:
on entry, on exit,
( a a a a a a a ) ( a a h h h h a )
( a a a a a a ) ( a h h h h a )
( a a a a a a ) ( h h h h h h )
( a a a a a a ) ( v2 h h h h h )
( a a a a a a ) ( v2 v3 h h h h )
( a a a a a a ) ( v2 v3 v4 h h h )
( a ) ( a )
where a denotes an element of the original matrix A, h denotes a
modified element of the upper Hessenberg matrix H, and vi denotes an
element of the vector defining H(i).
This implementation follows the hybrid algorithm and notations described in
S. Tomov and J. Dongarra, "Accelerating the reduction to upper Hessenberg
form through hybrid GPU-based computing," University of Tennessee Computer
Science Technical Report, UT-CS-09-642 (also LAPACK Working Note 219),
May 24, 2009.
This version stores the T matrices in dT, for later use in magma_sorghr.
===================================================================== */
#define A( i, j ) ( A + (i) + (j)*lda)
#define dA( i, j ) (dA + (i) + (j-ilo)*ldda)
float c_one = MAGMA_S_ONE;
float c_zero = MAGMA_S_ZERO;
magma_int_t nb = magma_get_sgehrd_nb(n);
magma_int_t ldda = n; // assumed in slahru
magma_int_t nh, iws;
magma_int_t iinfo;
magma_int_t ldwork;
magma_int_t lquery;
*info = 0;
iws = n*nb;
work[0] = MAGMA_S_MAKE( iws, 0 );
lquery = lwork == -1;
if (n < 0) {
*info = -1;
} else if (ilo < 1 || ilo > max(1,n)) {
*info = -2;
} else if (ihi < min(ilo,n) || ihi > n) {
*info = -3;
} else if (lda < max(1,n)) {
*info = -5;
} else if (lwork < max(1,n) && ! lquery) {
*info = -8;
}
if (*info != 0) {
magma_xerbla( __func__, -(*info) );
return *info;
}
else if (lquery)
return *info;
// Adjust from 1-based indexing
ilo -= 1;
// Quick return if possible
nh = ihi - ilo;
if (nh <= 1) {
work[0] = c_one;
return *info;
}
// GPU workspace is:
// nb*ldda for dwork for slahru
// nb*ldda for dV
// n*ldda for dA
float *dwork;
if (MAGMA_SUCCESS != magma_smalloc( &dwork, 2*nb*ldda + n*ldda )) {
*info = MAGMA_ERR_DEVICE_ALLOC;
return *info;
}
float *dV = dwork + nb*ldda;
float *dA = dwork + nb*ldda*2;
ldwork = n;
magma_int_t i;
float *T, *dTi;
magma_smalloc_cpu( &T, nb*nb );
if ( T == NULL ) {
magma_free( dwork );
*info = MAGMA_ERR_HOST_ALLOC;
return *info;
}
// zero first block of V, which is lower triangular
szero_nbxnb_block(nb, dV, ldda);
// Set elements 0:ILO-1 and IHI-1:N-2 of TAU to zero
for(i = 0; i < ilo; ++i)
tau[i] = c_zero;
for(i = max(0,ihi-1); i < n-1; ++i)
tau[i] = c_zero;
for(i=0; i < nb*nb; i += 4)
T[i] = T[i+1] = T[i+2] = T[i+3] = c_zero;
magmablas_slaset( 'F', nb, n, dT, nb );
// If not enough workspace, use unblocked code
if ( lwork < iws ) {
nb = 1;
}
if (nb == 1 || nb > nh) {
// Use unblocked code below
i = ilo;
}
else {
// Use blocked code
// Copy the matrix to the GPU
magma_ssetmatrix( n, n-ilo, A(0,ilo), lda, dA, ldda );
for (i = ilo; i < ihi-1 - nb; i += nb) {
// Reduce columns i:i+nb-1 to Hessenberg form, returning the
// matrices V and T of the block reflector H = I - V*T*V'
// which performs the reduction, and also the matrix Y = A*V*T
// Get the current panel (no need for the 1st iteration)
magma_sgetmatrix( ihi-i, nb,
dA(i,i), ldda,
A (i,i), lda );
// add 1 to i for 1-based index
magma_slahr2( ihi, i+1, nb,
dA(0,i),
dV,
A (0,i), lda,
&tau[i], T, nb, work, ldwork);
// Copy T from the CPU to dT on the GPU
dTi = dT + (i - ilo)*nb;
magma_ssetmatrix( nb, nb, T, nb, dTi, nb );
magma_slahru( n, ihi, i, nb,
A (0,i), lda,
dA(0,i), // dA
dA(i,i), // dY, stored over current panel
dV, dTi, dwork );
}
// Copy remainder to host
magma_sgetmatrix( n, n-i,
dA(0,i), ldda,
A (0,i), lda );
}
// Use unblocked code to reduce the rest of the matrix
// add 1 to i for 1-based index
i += 1;
lapackf77_sgehd2(&n, &i, &ihi, A, &lda, tau, work, &iinfo);
work[0] = MAGMA_S_MAKE( iws, 0 );
magma_free( dwork );
magma_free_cpu( T );
return *info;
} /* magma_sgehrd */