?lags2

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

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ID 766686

Date 4/28/2026

Version

Public

Computes 2-by-2 orthogonal matrices U, V, and Q, and applies them to matrices A and B such that the rows of the transformed A and B are parallel.

call slags2 ( upper , a1 , a2 , a3 , b1 , b2 , b3 , csu , snu , csv , snv , csq , snq )

call dlags2 ( upper , a1 , a2 , a3 , b1 , b2 , b3 , csu , snu , csv , snv , csq , snq )

call clags2 ( upper , a1 , a2 , a3 , b1 , b2 , b3 , csu , snu , csv , snv , csq , snq )

call zlags2 ( upper , a1 , a2 , a3 , b1 , b2 , b3 , csu , snu , csv , snv , csq , snq )

slags2 dlags2 clags2 zlags2

For real flavors, the routine computes 2-by-2 orthogonal matrices U , V and Q , such that if upper = .TRUE. , then

and

or if upper = .FALSE. , then

and

The rows of the transformed A and B are parallel, where

Here Z^:code:`T` denotes the transpose of Z .

For complex flavors, the routine computes 2-by-2 unitary matrices U , V and Q , such that if upper = .TRUE. , then

and

or if upper = .FALSE. , then

and

The rows of the transformed A and B are parallel, where

upper: LOGICAL . If upper = .TRUE. , the input matrices A and B are upper triangular; If upper = .FALSE. , the input matrices A and B are lower triangular.
a1 , a3: REAL for slags2 and clags2 DOUBLE PRECISION for dlags2 and zlags2
a2: REAL for slags2 DOUBLE PRECISION for dlags2 COMPLEX for clags2 COMPLEX*16 for zlags2 On entry, a1, a2 and a3 are elements of the input 2-by-2 upper (lower) triangular matrix A .
b1 , b3: REAL for slags2 and clags2 DOUBLE PRECISION for dlags2 and zlags2
b2: REAL for slags2 DOUBLE PRECISION for dlags2 COMPLEX for clags2 COMPLEX*16 for zlags2 On entry, b1, b2 and b3 are elements of the input 2-by-2 upper (lower) triangular matrix B .

csu: REAL for slags2 and clags2 DOUBLE PRECISION for dlags2 and zlags2 Element of the desired orthogonal matrix U .
snu: REAL for slags2 DOUBLE PRECISION for dlags2 Element of the desired orthogonal matrix U . COMPLEX for clags2 COMPLEX*16 for zlags2
csv: REAL for slags2 and clags2 DOUBLE PRECISION for dlags2 and zlags2 Element of the desired orthogonal matrix V .
snv: REAL for slags2 DOUBLE PRECISION for dlags2 COMPLEX for clags2 COMPLEX*16 for zlags2 Element of the desired orthogonal matrix V .
csq: REAL for slags2 and clags2 DOUBLE PRECISION for dlags2 and zlags2 Element of the desired orthogonal matrix Q .
snq: REAL for slags2 DOUBLE PRECISION for dlags2 Element of the desired orthogonal matrix Q . COMPLEX for clags2 COMPLEX*16 for zlags2