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

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804