SLAQSY(3)

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🌸 NAME

The NAME line is literally this source file path, no cap:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/slaqsy.f

🦋 SYNOPSIS

Functions/Subroutines

subroutine SLAQSY (uplo, n, a, lda, s, scond, amax, equed)

SLAQSY scales a symmetric/Hermitian matrix, using scaling factors computed by spoequ.

💫 Function/Subroutine Documentation

subroutine SLAQSY (character uplo, integer n, real, dimension( lda, * ) a,
    integer lda, real, dimension( * ) s, real scond, real amax, character
    equed)

SLAQSY scales a symmetric/Hermitian matrix, using scaling factors computed by spoequ.

🎯 Purpose

SLAQSY equilibrates a symmetric matrix A using the scaling factors in the vector S.

🧸 Parameters

• UPLO — CHARACTER*1. Specifies whether the upper or lower triangular part of the symmetric matrix A is stored. Values: 'U' = upper triangular; 'L' = lower triangular.
• N — INTEGER. The order of the matrix A. Constraint: N >= 0.
• A — REAL array, dimension (LDA,N). On entry, the symmetric matrix A. If UPLO = 'U', the leading n by n upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading n by n lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced.

On exit, if EQUED = 'Y', the equilibrated matrix: diag(S) * A * diag(S).

• LDA — INTEGER. The leading dimension of the array A. Constraint: LDA >= max(N,1).
• S — REAL array, dimension (N). The scale factors for A.
• SCOND — REAL. Ratio of the smallest S(i) to the largest S(i).
• AMAX — REAL. Absolute value of largest matrix entry.
• EQUED — CHARACTER*1. Specifies whether or not equilibration was done. Values: 'N' = no equilibration; 'Y' = equilibration was done, i.e., A has been replaced by diag(S) * A * diag(S).

🔍 Internal Parameters

• THRESH — a threshold value used to decide if scaling should be done based on the ratio of the scaling factors. If SCOND < THRESH, scaling is done.
• LARGE and SMALL — threshold values used to decide if scaling should be done based on the absolute size of the largest matrix element. If AMAX > LARGE or AMAX < SMALL, scaling is done.

👑 Author

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

Definition at line 132 of file slaqsy.f.

👑 Author (the Doxygen one)

Generated automatically by Doxygen for LAPACK from the source code.

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