SRC/ssyev.f(3)

💖 SRC/ssyev.f 💖

okay so bestie, welcome to the Library Functions Manual ✨ this is the page for SRC/ssyev.f, and honestly? it's giving linear algebra main character energy. buckle up 🎀

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🌸 NAME 🌸

SRC/ssyev.f — the file, the myth, the legend 🦋

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✨ SYNOPSIS ✨

Functions/Subroutines

• subroutine ssyev (jobz, uplo, n, a, lda, w, work, lwork, info) — SSYEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for SY matrices. that's the whole vibe 💅

Function/Subroutine Documentation

subroutine ssyev (character jobz, character uplo, integer n, real,
    dimension( lda, * ) a, integer lda, real, dimension( * ) w, real,
    dimension( * ) work, integer lwork, integer info)

SSYEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for SY matrices. no cap 🔥

🧚 Purpose:

!>
!> SSYEV computes all eigenvalues and, optionally, eigenvectors of a
!> real symmetric matrix A.
!>

so like… all the eigenvalues, and if you ask nicely, the eigenvectors too 🫶

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🎀 Parameters 🎀

• JOBZ — JOBZ is CHARACTER*1. the personality selector, basically:
  • = 'N': compute eigenvalues only;
  • = 'V': compute eigenvalues and eigenvectors.

pick your fighter 💅

• UPLO — UPLO is CHARACTER*1. which triangle of A is the real one:
  • = 'U': upper triangle of A is stored;
  • = 'L': lower triangle of A is stored.

(the other triangle is just… not invited to the party 🙈)

• N — N is INTEGER. the order of the matrix A. N >= 0. yes, zero is allowed, she's valid too 👑
• A — A is 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. if UPLO = 'L', the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A.
  • on exit: if JOBZ = 'V', then if INFO = 0, A contains the orthonormal eigenvectors of the matrix A.
  • if JOBZ = 'N', then on exit the lower triangle (if UPLO='L') or the upper triangle (if UPLO='U') of A, including the diagonal, is destroyed 💀 like, gone gone. she did not survive the process. be aware, bestie.
• LDA — LDA is INTEGER. the leading dimension of the array A. LDA >= max(1,N). respect the boundary ✨
• W — W is REAL array, dimension (N). if INFO = 0, the eigenvalues in ascending order. sorted, organized, iconic 🌈
• WORK — WORK is REAL array, dimension (MAX(1,LWORK)). on exit, if INFO = 0, WORK(1) returns the optimal LWORK. she's a little hint-giver 🎀
• LWORK — LWORK is INTEGER. the length of the array WORK. LWORK >= max(1,3*N-1). for optimal efficiency, LWORK >= (NB+2)*N, where NB is the blocksize for SSYTRD returned by ILAENV.

if LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA. very "just asking, not committing" of her 💅

• INFO — INFO is INTEGER. the status report:
  • = 0: successful exit 🎉
  • < 0: if INFO = -i, the i-th argument had an illegal value 🙈
  • > 0: if INFO = i, the algorithm failed to converge; i off-diagonal elements of an intermediate tridiagonal form did not converge to zero. 😭 she tried her best but the tridiagonal situation was not cooperating.

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👑 Author 👑

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

Definition at line 131 of file ssyev.f. ⭐

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💜 Author 💜

Generated automatically by Doxygen for LAPACK from the source code. so yes, a robot transcribed this and we're all grateful 🫶

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ngl this whole page is a glow-up for your linear algebra era. eigenvalues? computed. eigenvectors? optional but slay. triangle of A? destroyed if you said JOBZ = 'N'. periodt. 💅

big kiss from LAPACK, Version 3.12.0, dated the day this page was born — see you in the SEE ALSOs of your dreams, bestie 🦋💖🎀