Developer Reference

  • 2020.2
  • 07/15/2020
  • Public Content
Contents

?las2

Computes singular values of a 2-by-2 triangular matrix.

Syntax

call slas2
(
f
,
g
,
h
,
ssmin
,
ssmax
)
call dlas2
(
f
,
g
,
h
,
ssmin
,
ssmax
)
Include Files
  • mkl.fi
Description
The routine
?las2
computes the singular values of the 2-by-2 matrix
Equation
On return,
ssmin
is the smaller singular value and
SSMAX
is the larger singular value.
Input Parameters
f
,
g
,
h
REAL
for
slas2
DOUBLE PRECISION
for
dlas2
The (1,1), (1,2) and (2,2) elements of the 2-by-2 matrix, respectively.
Output Parameters
ssmin
,
ssmax
REAL
for
slas2
DOUBLE PRECISION
for
dlas2
The smaller and the larger singular values, respectively.
Application Notes
Barring over/underflow, all output quantities are correct to within a few units in the last place (
ulps
), even in the absence of a guard digit in addition/subtraction. In ieee arithmetic, the code works correctly if one matrix element is infinite. Overflow will not occur unless the largest singular value itself overflows, or is within a few ulps of overflow. (On machines with partial overflow, like the Cray, overflow may occur if the largest singular value is within a factor of 2 of overflow.) Underflow is harmless if underflow is gradual. Otherwise, results may correspond to a matrix modified by perturbations of size near the underflow threshold.

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