Contents

# p?lantr

Returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element, of a triangular matrix.

## Syntax

Include Files
• mkl_scalapack.h
Description
The
p?lantr
function
returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a trapezoidal or triangular 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 trapezoidal,
=
'L'
: Lower trapezoidal.
Note that sub(
A
) is triangular instead of trapezoidal if
m
=
n
.
diag
(global)
Specifies whether the distributed matrix sub(
A
) has unit diagonal.
=
'N'
: Non-unit diagonal.
=
'U'
: Unit diagonal.
m
(global)
The number of rows in the distributed matrix sub(
A
). When
m
= 0
,
p?lantr
is set to zero.
m
0
.
n
(global)
The number of columns in the distributed matrix sub(
A
). When
n
= 0
,
p?lantr
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
).
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 size
lwork
.
lwork
0
if
norm
=
'M'
or
'm'
(not referenced),
nq
0 if
norm
= '1',
'O'
or
'o'
,
mp
0 if
norm
=
'I'
or
'i'
,
0 if
norm
=
'F'
,
'f'
,
'E'
or
'e'
(not referenced),
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
)
,
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.