?lagsy

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 12/16/2022

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?lagsy

Generates a symmetric matrix by pre- and post- multiplying a real diagonal matrix with a random unitary matrix .

Syntax

lapack_int LAPACKE_slagsy (int matrix_layout , lapack_int n , lapack_int k , const float * d , float * a , lapack_int lda , lapack_int * iseed );

lapack_int LAPACKE_dlagsy (int matrix_layout , lapack_int n , lapack_int k , const double * d , double * a , lapack_int lda , lapack_int * iseed );

lapack_int LAPACKE_clagsy (int matrix_layout , lapack_int n , lapack_int k , const float * d , lapack_complex_float * a , lapack_int lda , lapack_int * iseed );

lapack_int LAPACKE_zlagsy (int matrix_layout , lapack_int n , lapack_int k , const double * d , lapack_complex_double * a , lapack_int lda , lapack_int * iseed );

Include Files

mkl.h

Description

The ?lagsy routine generates a symmetric matrix A by pre- and post- multiplying a real diagonal matrix D with a random matrix U:

A := U*D*U^T,

where U is orthogonal for real flavors and unitary for complex flavors. The semi-bandwidth may then be reduced to k by additional unitary transformations.

Input Parameters

A <datatype> placeholder, if present, is used for the C interface data types in the C interface section above. See C Interface Conventions for the C interface principal conventions and type definitions.

n: The order of the matrix A (n≥ 0).
k: The number of nonzero subdiagonals within the band of A (0 ≤k≤n-1).
d: The array d with the dimension of (n) contains the diagonal elements of the diagonal matrix D.
lda: The leading dimension of the array a (lda≥n).
iseed: The array iseed with the dimension of 4 contains the seed of the random number generator. The elements must be between 0 and 4095 and iseed[3] must be odd.

Output Parameters

a: The array aof size max (1,lda*n) contains the generated symmetric n-by-n matrix D.
iseed: The array iseed contains the updated seed on exit.

Return Values

This function returns a value info.

If info = 0, the execution is successful.

If info < 0, the i-th parameter had an illegal value.

If info = -1011, memory allocation error occurred.

Parent topic: LAPACK Test Functions and Routines

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Developer Reference for Intel® oneAPI Math Kernel Library for C

?lagsy