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

okay bestie, we're in the Library Functions Manual for /home/abui...RC/chbev.f(3) — and it's giving "LAPACK girlie with a very specific band-matrix moment." 🎀

💖 NAME 💖

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

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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. iconic. 💅

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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 🌸

Bestie, the purpose is right there: CHBEV computes all the eigenvalues and, optionally, eigenvectors of a complex Hermitian band matrix A. no cap, that's the whole assignment. 💖

🦋 Parameters 🦋

• JOBZ — CHARACTER*1. This is the "what do you actually want" switch:
  • = 'N': Compute eigenvalues only;
  • = 'V': Compute eigenvalues and eigenvectors.
• UPLO — CHARACTER*1. Which triangle are we storing, bestie?
  • = 'U': Upper triangle of A is stored;
  • = 'L': Lower triangle of A is stored.
• N — INTEGER. The order of the matrix A. N >= 0.
• KD — INTEGER. The number of superdiagonals of the matrix A if UPLO = 'U', or the number of subdiagonals if UPLO = 'L'. KD >= 0.
• AB — 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 — INTEGER. The leading dimension of the array AB. LDAB >= KD + 1.
• W — REAL array, dimension (N). If INFO = 0, the eigenvalues in ascending order. slay ordering. ⭐
• Z — 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. not me checking Z when JOBZ is N 🙈
• LDZ — INTEGER. The leading dimension of the array Z. LDZ >= 1, and if JOBZ = 'V', LDZ >= max(1,N).
• WORK — COMPLEX array, dimension (N).
• RWORK — REAL array, dimension (max(1,3*N-2)).
• INFO — INTEGER. The receipts:
  • = 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.

heads up bestie: negative INFO means somebody passed an illegal argument; positive INFO means convergence said "nope." do not ignore it. 💀

👑 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 🌈

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