SRC/sspev.f(3)

🌸 NAME 🌸

okay so bestie, this page is SRC/sspev.f from the Library Functions Manual, and it’s giving “LAPACK routine that actually slays linear algebra” energy 💅✨

✨ SYNOPSIS ✨

🫶 Functions/Subroutines

subroutine sspev (jobz, uplo, n, ap, w, z, ldz, work, info)

SSPEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices 🦋

💅 Function/Subroutine Documentation 💅

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

SSPEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices 🌈

🎀 Purpose 🎀

SSPEV computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage. periodt. 💖

🌈 Parameters 🌈

JOBZ

JOBZ is CHARACTER*1

• = 'N': Compute eigenvalues only;
• = 'V': Compute eigenvalues and eigenvectors.

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. 🫶

AP

AP is REAL array, dimension (N*(N+1)/2)

On entry, the upper or lower triangle of the symmetric 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. no cap, it gets rewritten 😭

W

W is REAL array, dimension (N)

If INFO = 0, the eigenvalues in ascending order. ⭐

Z

Z is REAL 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 REAL array, dimension (3*N) 🍓

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 129 of file sspev.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code. 🧚

---

That’s the whole page, bestie — LAPACK Version 3.12.0 · SRC/sspev.f(3) · iconic, automated, and fully documented 💜✨