?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 ?lasorte routine 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.

Optimization Notice

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

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

For more complete information about compiler optimizations, see our Optimization Notice.