Contents

# p?lansy, p?lanhe

Returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element, of a real symmetric or a complex Hermitian matrix.

## Syntax

Include Files
• mkl_scalapack.h
Description
The
p?lansy
and
p?lanhe
functions
return the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a distributed matrix
sub(
A
) =
A
(
ia
:
ia
+
m
-1
,
ja
:
ja
+
n
-1)
.
Input Parameters
norm
(global) Specifies what value is returned by the
function
:
=
'M'
or
'm':
val
=
max
(
abs
(
A
ij
))
, largest absolute value of the matrix
A
, it s not a matrix norm.
=
'1'
or
'O'
or
'o':
val
=
norm1
(
A
)
, 1-norm of the matrix
A
(maximum column sum),
=
'I'
or
'i':
val
=
normI
(
A
)
, infinity norm of the matrix
A
(maximum row sum),
=
'F'
,
'f'
,
'E'
or
'e':
val
=
normF
(
A
)
, Frobenius norm of the matrix
A
(square root of sum of squares).
uplo
(global) Specifies whether the upper or lower triangular part of the symmetric matrix sub(
A
) is to be referenced.
=
'U'
: Upper triangular part of sub(
A
) is referenced,
=
'L'
: Lower triangular part of sub(
A
) is referenced.
n
(global)
The number of columns in the distributed matrix sub(
A
). When
n
= 0
,
p?lansy
is set to zero.
n
0.
a
(local).
Pointer into the local memory to an array of size
lld_a
*
LOCc
(
ja
+
n
-1)
containing the local pieces of the distributed matrix sub(
A
).
If
uplo
=
'U'
n
-by-
n
upper triangular part of sub(
A
) contains the upper triangular matrix whose norm is to be computed, and the strictly lower triangular part of this matrix is not referenced. If
uplo
=
'L'
n
-by-
n
lower triangular part of sub(
A
) contains the lower triangular matrix whose norm is to be computed, and the strictly upper triangular part of sub(
A
) is not referenced.
ia
,
ja
(global) The row and column indices in the global matrix
A
indicating the first row and the first column of the matrix sub(
A
), respectively.
desca
(global and local) array of size
dlen_
. The array descriptor for the distributed matrix
A
.
work
(local).
Array of size
lwork
.
lwork
0 if
norm
=
'M'
or
'm'
(not referenced),
2*
nq
0+
mp
0+
ldw
if
norm
= '1',
'O'
or
'o'
,
'I'
or
'i'
,
where
ldw
is given by:
if(
nprow
npcol
) then
ldw
=
mb_a
*iceil(iceil(
np
0,
mb_a
),(
lcm
/
nprow
))
else
ldw
= 0
end if
0 if
norm
=
'F'
,
'f'
,
'E'
or
'e'
(not referenced),
where
lcm
is the least common multiple of
nprow
and
npcol
,
lcm
= ilcm(
nprow
,
npcol
)
and
iceil
(
x
,
y
)
is a ScaLAPACK function that returns ceiling
(
x
/
y
)
.
iroffa
=
mod
(
ia
-1,
mb_a
),
icoffa
=
mod
(
ja
-1,
nb_a
),
iarow
=
indxg2p
(
ia
,
mb_a
,
myrow
,
rsrc_a
,
nprow
),
iacol
=
indxg2p
(
ja
,
nb_a
,
mycol
,
csrc_a
,
npcol
),
mp
0 =
numroc
(
m
+
iroffa
,
mb_a
,
myrow
,
iarow
,
nprow
),
nq
0 =
numroc
(
n
+
icoffa
,
nb_a
,
mycol
,
iacol
,
npcol
),
ilcm
,
iceil
,
indxg2p
, and
numroc
are ScaLAPACK tool functions;
myrow
,
mycol
,
nprow
, and
npcol
can be determined by calling the
function
blacs_gridinfo
.
Output Parameters
val
The value returned by the
function
.

#### Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.