Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

Contents

p?lassq

Updates a sum of squares represented in scaled form.

Syntax

void
pslassq
(
MKL_INT
*n
,
float
*x
,
MKL_INT
*ix
,
MKL_INT
*jx
,
MKL_INT
*descx
,
MKL_INT
*incx
,
float
*scale
,
float
*sumsq
);
void
pdlassq
(
MKL_INT
*n
,
double
*x
,
MKL_INT
*ix
,
MKL_INT
*jx
,
MKL_INT
*descx
,
MKL_INT
*incx
,
double
*scale
,
double
*sumsq
);
void
pclassq
(
MKL_INT
*n
,
MKL_Complex8
*x
,
MKL_INT
*ix
,
MKL_INT
*jx
,
MKL_INT
*descx
,
MKL_INT
*incx
,
float
*scale
,
float
*sumsq
);
void
pzlassq
(
MKL_INT
*n
,
MKL_Complex16
*x
,
MKL_INT
*ix
,
MKL_INT
*jx
,
MKL_INT
*descx
,
MKL_INT
*incx
,
double
*scale
,
double
*sumsq
);
Include Files
  • mkl_scalapack.h
Description
The
p?lassq
function
returns the values
scl
 and
smsq
 such that
scl
2
 *
smsq
 =
x
1
2
 + ... +
x
n
2
 +
scale
2
*
sumsq
,
where
x
i
= sub(
X
) =
X
(
ix
 + (
jx
-1)*
m_x
 + (
i
 - 1)*
incx
) for
pslassq/pdlassq
 ,
x
i
= sub(
X
) = abs(
X
(
ix
 + (
jx
-1)*
m_x
 + (
i
 - 1)*
incx
) for
pclassq/pzlassq
.
For real
functions
pslassq/pdlassq
 the value of
sumsq
 is assumed to be non-negative and
scl
 returns the value
scl
 = max(
scale
, abs(
x
i
)).
For complex
functions
pclassq/pzlassq
 the value of
sumsq
 is assumed to be at least unity and the value of
ssq
 will then satisfy
1.0
≤
ssq
≤
sumsq
 +2
n
Value
scale
 is assumed to be non-negative and
scl
 returns the value
For all
functions
p?lassq
 values
scale
 and
sumsq
 must be supplied in
scale
 and
sumsq
respectively, and
scale
 and
sumsq
are overwritten by
scl
 and
ssq
 respectively.
All
functions
p?lassq
 make only one pass through the vector sub(
X
).
Input Parameters
n
(global)
The length of the distributed vector sub(
x
 ).
x
The array that stores the
 vector for which a scaled sum of squares is computed:
x
[
ix
 + (
jx
-1)*
m_x
 + i*
incx
], 0
≤
i
 <
n
.
ix
(global)
The row index in the global matrix
X
 indicating the first row of sub(
X
).
jx
(global)
The column index in the global matrix
X
 indicating the first column of sub(
X
).
descx
(global and local) array of size
dlen_
.
The array descriptor for the distributed matrix
X
.
incx
(global)
The global increment for the elements of
X
. Only two values of
incx
 are supported in this version, namely 1 and
m_x
. The argument
incx
 must not equal zero.
scale
(local).
On entry, the value
scale
 in the equation above.
sumsq
(local)
On entry, the value
sumsq
 in the equation above.
Output Parameters
scale
(local).
On exit,
scale
 is overwritten with
sc
l
 , the scaling factor for the sum of squares.
sumsq
(local).
On exit,
sumsq
 is overwritten with the value
smsq,
 the basic sum of squares from which
scl
 has been factored out.

Product and Performance Information

1

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