/home/abui...RC/chpev.f(3)

🦋 chpev.f(3) — Library Functions Manual 🦋

okay so bestie, this is the LAPACK manual page energy for chpev.f(3) — the manual name is literally right there in the title, cute and accounted for. Let’s get into it 💅✨

💖 NAME 💖

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

✨ SYNOPSIS ✨

🌸 Functions/Subroutines 🌸

subroutine CHPEV (jobz, uplo, n, ap, w, z, ldz, work, rwork, info)
     CHPEV computes the eigenvalues and, optionally, the left and/or
     right eigenvectors for OTHER matrices

CHPEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices. That’s the whole little synopsis moment, no cap. 🫶

💅 Function/Subroutine Documentation 💅

Here’s the full signature, bestie — typed out exactly:

subroutine CHPEV (character jobz, character uplo, integer n, complex,
       dimension( * ) ap, real, dimension( * ) w, complex, dimension( ldz, * )
       z, integer ldz, complex, dimension( * ) work, real, dimension( * )
       rwork, integer info)

CHPEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices. Yes, it said it again. Iconic repetition behavior. 💫

🎯 Purpose 🎯

fr fr, the purpose is this: CHPEV computes all the eigenvalues and, optionally, the eigenvectors of a complex Hermitian matrix in packed storage. That’s the vibe check, and it passed. 😌💖

🧚 Parameters 🧚

• JOBZ — it’s CHARACTER*1. = 'N': compute eigenvalues only; = 'V': compute eigenvalues and eigenvectors. Pick your little path, bestie. 🌸
• UPLO — it’s CHARACTER*1. = 'U': upper triangle of A is stored; = 'L': lower triangle of A is stored. Choose your triangle era. 💅
• N — it’s INTEGER. The order of the matrix A. N >= 0. no negative-order nonsense here 🫶
• AP — it’s a COMPLEX array, dimension (N*(N+1)/2). On entry, it holds the upper or lower triangle of the Hermitian matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows:
  • if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
  • if UPLO = 'L', AP(i + (j-1)*(2*n-j)/2) = A(i,j) for j<=i<=n.

On exit, AP is overwritten by values generated during the reduction to tridiagonal form. If UPLO = 'U', the diagonal and first superdiagonal of the tridiagonal matrix T overwrite the corresponding elements of A, and if UPLO = 'L', the diagonal and first subdiagonal of T overwrite the corresponding elements of A. That’s a lot of overwriting, but she’s booked and busy 😭🔥

• W — it’s a REAL array, dimension (N). If INFO = 0, the eigenvalues in ascending order. Sorted and serving. ✨
• Z — it’s a COMPLEX array, dimension (LDZ, N). If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal eigenvectors of the matrix A, with the i-th column of Z holding the eigenvector associated with W(i). If JOBZ = 'N', then Z is not referenced. Respect the not-referenced boundary, bestie 🫶
• LDZ — it’s INTEGER. The leading dimension of the array Z. LDZ >= 1, and if JOBZ = 'V', LDZ >= max(1,N). Rules are rules 💅
• WORK — it’s a COMPLEX array, dimension (max(1, 2*N-1)). 🧚
• RWORK — it’s a REAL array, dimension (max(1, 3*N-2)). 🌈
• INFO — it’s INTEGER. = 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. So if INFO is acting up, that’s the tea 💀

🌟 Author 🌟

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

Definition at line 136 of file chpev.f.

🤖 Author 🤖

Generated automatically by Doxygen for LAPACK from the source code.

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and that’s the whole page, bestie 🎀 signing off with LAPACK Version 3.12.0 and the footer path /home/abui...RC/chpev.f(3) doing its little cameo at the end. mwah 💋✨