CHEGST(3)

💅 CHEGST(3) — Library Functions Manual 💅

Bestie, welcome to the manual page for CHEGST — yes, the Library Functions Manual one, and the vibe is very LAPACK. The page header/footer abbreviates the source path as /home/abui...RC/chegst.f(3) (iykyk), and the full source path is in NAME below. 🦋

🌈 NAME 🌈

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

That's the file path this page is named after, periodt. 💖

✨ SYNOPSIS ✨

Functions/Subroutines

subroutine CHEGST (itype, uplo, n, a, lda, b, ldb, info)
    CHEGST

🌸 Function/Subroutine Documentation 🌸

subroutine CHEGST (...)

subroutine CHEGST (integer itype, character uplo, integer n, complex,
    dimension( lda, * ) a, integer lda, complex, dimension( ldb, * ) b,
    integer ldb, integer info)
    CHEGST

🎯 Purpose 🎯

Okay so here's the whole point: CHEGST reduces a complex Hermitian-definite generalized eigenproblem to standard form. ✨

• If ITYPE = 1, the problem is A*x = lambda*B*x, and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H).
• If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H*A*L.

And do not forget, bestie: B must have been previously factorized as U**H*U or L*L**H by CPOTRF. 🫶

🎀 Parameters 🎀

• ITYPE — ITYPE is INTEGER
  • = 1: compute inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H).
  • = 2 or 3: compute U*A*U**H or L**H*A*L.
• UPLO — UPLO is CHARACTER*1
  • = 'U': Upper triangle of A is stored and B is factored as U**H*U.
  • = 'L': Lower triangle of A is stored and B is factored as L*L**H.
• N — N is INTEGER. The order of the matrices A and B. N >= 0.
• A — A is COMPLEX array, dimension (LDA,N).
  • On entry, the Hermitian matrix A. If UPLO = 'U', the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced.
  • On exit, if INFO = 0, the transformed matrix, stored in the same format as A.
• LDA — LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,N).
• B — B is COMPLEX array, dimension (LDB,N).
  • The triangular factor from the Cholesky factorization of B, as returned by CPOTRF.
  • B is modified by the routine but restored on exit. 🙈
• LDB — LDB is INTEGER. The leading dimension of the array B. LDB >= max(1,N).
• INFO — INFO is INTEGER
  • = 0: successful exit.
  • < 0: if INFO = -i, the i-th argument had an illegal value.

👑 Author 👑

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

Definition at line 127 of file chegst.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

---

Sign-off, bestie: this whole page is from LAPACK, Version 3.12.0, and the footer path is /home/abui...RC/chegst.f(3). The original footer doesn't give a separate date, just that source/version line — so no invented date, just vibes and exact facts. Mwah 💖🎀🦋