ZHEGST(3)

💖 NAME 💖

Bestie, this is the ZHEGST(3) page from the Library Functions Manual, and the source file it’s repping is /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/zhegst.f.

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✨ SYNOPSIS ✨

Functions/Subroutines lineup, no cap:

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

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🦋 FUNCTION/SUBROUTINE DOCUMENTATION 🦋

subroutine ZHEGST (integer itype, character uplo, integer n, complex*16,
    dimension( lda, * ) a, integer lda, complex*16, dimension( ldb, * ) b,
    integer ldb, integer info)
    ZHEGST

🌸 PURPOSE 🌸

Okay so ZHEGST reduces a complex Hermitian-definite generalized eigenproblem to standard form. Iconic behavior honestly.

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.

🫶 Important caveat, bestie: B must have been previously factorized as U**H*U or L*L**H by ZPOTRF.

🎀 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*16 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*16 array, dimension (LDB,N). The triangular factor from the Cholesky factorization of B, as returned by ZPOTRF. 🫶 Key detail: 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 zhegst.f.

🌟 AUTHOR 🌟

Generated automatically by Doxygen for LAPACK from the source code.

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Catch you later, bestie 💖 — this is LAPACK Version 3.12.0, and the page path is /home/abui...RC/zhegst.f(3). Slay. 💅✨