SRC/chbev.f(3)

💖 NAME 💖

Okay bestie, this page is SRC/chbev.f from the Library Functions Manual, and it's a Fortran subroutine situation with major linear algebra main-character energy. It documents CHBEV, no cap. ✨

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✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine chbev (jobz, uplo, n, kd, ab, ldab, w, z, ldz, work, rwork,
           info)

CHBEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices — yes, “OTHER” is literally in the official description, bestie 💅

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🛠️ Function/Subroutine Documentation 🛠️

subroutine chbev (character jobz, character uplo, integer n, integer kd,
       complex, dimension( ldab, * ) ab, integer ldab, real, dimension( * ) w,
       complex, dimension( ldz, * ) z, integer ldz, complex, dimension( * )
       work, real, dimension( * ) rwork, integer info)

CHBEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices 🫶

🎯 Purpose 🎯

CHBEV computes all the eigenvalues and, optionally, eigenvectors of a complex Hermitian band matrix A. Slay. 🔥

🌸 Parameters 🌸

• JOBZ — JOBZ is CHARACTER*1. = 'N': compute eigenvalues only; = 'V': compute eigenvalues and eigenvectors. Choose your vibe ✨
• UPLO — UPLO is CHARACTER*1. = 'U': upper triangle of A is stored; = 'L': lower triangle of A is stored.
• N — N is INTEGER. The order of the matrix A. N >= 0.
• KD — KD is INTEGER. The number of superdiagonals of the matrix A if UPLO = 'U', or the number of subdiagonals if UPLO = 'L'. KD >= 0.
• AB — AB is COMPLEX array, dimension (LDAB, N). On entry, the upper or lower triangle of the Hermitian band matrix A, stored in the first KD+1 rows of the array. The j-th column of A is stored in the j-th column of the array AB as follows:

if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j;
if UPLO = 'L', AB(1+i-j,j)    = A(i,j) for j<=i<=min(n,j+kd).

On exit, AB is overwritten by values generated during the reduction to tridiagonal form. If UPLO = 'U', the first superdiagonal and the diagonal of the tridiagonal matrix T are returned in rows KD and KD+1 of AB, and if UPLO = 'L', the diagonal and first subdiagonal of T are returned in the first two rows of AB. 🌀

• LDAB — LDAB is INTEGER. The leading dimension of the array AB. LDAB >= KD + 1.
• W — W is REAL array, dimension (N). If INFO = 0, the eigenvalues in ascending order. Iconic. 👑
• Z — Z is 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.
• LDZ — LDZ is INTEGER. The leading dimension of the array Z. LDZ >= 1, and if JOBZ = 'V', LDZ >= max(1,N).
• WORK — WORK is COMPLEX array, dimension (N).
• RWORK — RWORK is REAL array, dimension (max(1,3*N-2)).
• INFO — INFO is 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. 😭

🎀 Author 🎀

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

Definition at line 150 of file chbev.f.

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🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

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Cute footer sign-off, bestie: LAPACK — Version 3.12.0 — SRC/chbev.f(3) 🫶💖✨