Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

ID 766686
Date 3/31/2023
Public

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?lasorte

Sorts eigenpairs by real and complex data types.

Syntax

call slasorte(s, lds, j, out, info)

call dlasorte(s, lds, j, out, info)

Description

The ?lasorteroutine sorts eigenpairs so that real eigenpairs are together and complex eigenpairs are together. This helps to employ 2x2 shifts easily since every second subdiagonal is guaranteed to be zero. This routine does no parallel work and makes no calls.

Product and Performance Information

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

Notice revision #20201201

Input Parameters
s

(local)

REAL for slasorte

DOUBLE PRECISION for dlasorte

Array of size lds.

On entry, a matrix already in Schur form.

lds

(local) INTEGER.

On entry, the leading dimension of the array s; unchanged on exit.

j

(local) INTEGER.

On entry, the order of the matrix S; unchanged on exit.

out

(local)

REAL for slasorte

DOUBLE PRECISION for dlasorte

Array of size 2*j. The work buffer required by the routine.

info

(local) INTEGER.

Set, if the input matrix had an odd number of real eigenvalues and things could not be paired or if the input matrix S was not originally in Schur form. 0 indicates successful completion.

Output Parameters
s

On exit, the diagonal blocks of S have been rewritten to pair the eigenvalues. The resulting matrix is no longer similar to the input.

out

Work buffer.

See Also