p?laconsb
p?laconsb
Looks for two consecutive small subdiagonal elements.
Syntax
void
pslaconsb
(
const
float
*
a
,
const
MKL_INT
*
desca
,
const
MKL_INT
*
i
,
const
MKL_INT
*
l
,
MKL_INT
*
m
,
const
float
*
h44
,
const
float
*
h33
,
const
float
*
h43h34
,
float
*
buf
,
const
MKL_INT
*
lwork
);
void
pdlaconsb
(
const
double
*
a
,
const
MKL_INT
*
desca
,
const
MKL_INT
*
i
,
const
MKL_INT
*
l
,
MKL_INT
*
m
,
const
double
*
h44
,
const
double
*
h33
,
const
double
*
h43h34
,
double
*
buf
,
const
MKL_INT
*
lwork
);
void
pclaconsb
(
const
MKL_Complex8
*
a
,
const
MKL_INT
*
desca
,
const
MKL_INT
*
i
,
const
MKL_INT
*
l
,
MKL_INT
*
m
,
const
MKL_Complex8
*
h44
,
const
MKL_Complex8
*
h33
,
const
MKL_Complex8
*
h43h34
,
MKL_Complex8
*
buf
,
const
MKL_INT
*
lwork
);
void
pzlaconsb
(
const
MKL_Complex16
*
a
,
const
MKL_INT
*
desca
,
const
MKL_INT
*
i
,
const
MKL_INT
*
l
,
MKL_INT
*
m
,
const
MKL_Complex16
*
h44
,
const
MKL_Complex16
*
h33
,
const
MKL_Complex16
*
h43h34
,
MKL_Complex16
*
buf
,
const
MKL_INT
*
lwork
);
Include Files
- mkl_scalapack.h
Description
The
p?laconsb
function
looks for two consecutive small subdiagonal elements by analyzing the effect of starting a double shift QR
iteration given by h44
, h33
, and h43h34
to see if this process makes a subdiagonal negligible.Input Parameters
- a
- (local)Array of size. On entry, the Hessenberg matrix whose tridiagonal part is being scanned. Unchanged on exit.lld_a*LOCc(n_a)
- desca
- (global and local)Array of sizedlen_. The array descriptor for the distributed matrixA.
- i
- (global)The global location of the bottom of the unreduced submatrix ofA. Unchanged on exit.
- l
- (global)The global location of the top of the unreduced submatrix ofA. Unchanged on exit.
- h44,h33,h43h34
- (global).These three values are for the double shiftQRiteration.
- lwork
- (local)This must be at least7*ceil(ceil( (. Herei-l)/mb_a)/lcm(nprow,npcol))lcmis the least common multiple andis the logical grid size.nprow*npcol
Output Parameters
- m
- (global). On exit, this yields the starting location of theQRdouble shift. This will satisfy:l≤m≤i-2.
- buf
- (local).Array of sizelwork.