SSTT22(3)

💖 NAME 💖

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/EIG/sstt22.f

Hey bestie, you're on the sstt22.f(3) page in the LAPACK Library Functions Manual — header path energy is /home/abui...IG/sstt22.f(3). This whole page is about the SSTT22 subroutine, and it's lowkey iconic. 🦋

✨ SYNOPSIS ✨

Functions/Subroutines

subroutine SSTT22 (n, m, kband, ad, ae, sd, se, u, ldu, work, ldwork,
    result)
    SSTT22

🌸 Function/Subroutine Documentation 🌸

subroutine SSTT22 (integer n, integer m, integer kband, real, dimension( * )
    ad, real, dimension( * ) ae, real, dimension( * ) sd, real, dimension( *
    ) se, real, dimension( ldu, * ) u, integer ldu, real, dimension( ldwork,
    * ) work, integer ldwork, real, dimension( 2 ) result)
    SSTT22

🎀 Purpose 🎀

Okay so SSTT22 checks a set of M eigenvalues and eigenvectors, bestie. The vibe is:

A U = U S

where A is symmetric tridiagonal, the columns of U are orthogonal, and S is diagonal (if KBAND=0) or symmetric tridiagonal (if KBAND=1). Two tests are performed:

RESULT(1) = | U' A U - S | / ( |A| m ulp )

RESULT(2) = | I - U'U | / ( m ulp )

💅 Parameters 💅

• N — N is INTEGER. The size of the matrix. If it is zero, SSTT22 does nothing. It must be at least zero.
• M — M is INTEGER. The number of eigenpairs to check. If it is zero, SSTT22 does nothing. It must be at least zero.
• KBAND — KBAND is INTEGER. The bandwidth of the matrix S. It may only be zero or one. If zero, then S is diagonal, and SE is not referenced. If one, then S is symmetric tri-diagonal.
• AD — AD is REAL array, dimension (N). The diagonal of the original (unfactored) matrix A. A is assumed to be symmetric tridiagonal.
• AE — AE is REAL array, dimension (N). The off-diagonal of the original (unfactored) matrix A. A is assumed to be symmetric tridiagonal. AE(1) is ignored, AE(2) is the (1,2) and (2,1) element, etc.
• SD — SD is REAL array, dimension (N). The diagonal of the (symmetric tri-) diagonal matrix S.
• SE — SE is REAL array, dimension (N). The off-diagonal of the (symmetric tri-) diagonal matrix S. Not referenced if KBSND=0. If KBAND=1, then AE(1) is ignored, SE(2) is the (1,2) and (2,1) element, etc.
• U — U is REAL array, dimension (LDU, N). The orthogonal matrix in the decomposition.
• LDU — LDU is INTEGER. The leading dimension of U. LDU must be at least N.
• WORK — WORK is REAL array, dimension (LDWORK, M+1).
• LDWORK — LDWORK is INTEGER. The leading dimension of WORK. LDWORK must be at least max(1,M).
• RESULT — RESULT is REAL array, dimension (2). The values computed by the two tests described above. The values are currently limited to 1/ulp, to avoid overflow.

👑 Author 👑

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

Definition at line 137 of file sstt22.f.

🧚 Author 🧚

Generated automatically by Doxygen for LAPACK from the source code.

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Okay bestie, cute little source/version sign-off: this is LAPACK Version 3.12.0, page /home/abui...IG/sstt22.f(3) — go slay your linear algebra, mwah 💋✨