Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
?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
slas2 dlas2
The routine ?las2 computes the singular values of the 2-by-2 matrix
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. Underflow is harmless if it is gradual. Otherwise, results may correspond to a matrix modified by perturbations of size near the underflow threshold.