ZHEGS2(3)

ZHEGS2(3) — Library Functions Manual 🎀

okay bestie, welcome to the ZHEGS2 page — the unblocked-algorithm era is here and it’s honestly iconic. 💅

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✨ NAME ✨

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/zhegs2.f

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🌸 SYNOPSIS 🌸

Functions/Subroutines

• subroutine ZHEGS2 (itype, uplo, n, a, lda, b, ldb, info) — ZHEGS2 reduces a Hermitian definite generalized eigenproblem to standard form, using the factorization results obtained from cpotrf (unblocked algorithm).

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🦋 Function/Subroutine Documentation 🦋

subroutine ZHEGS2 (integer itype, character uplo, integer n, complex*16,
       dimension( lda, * ) a, integer lda, complex*16, dimension( ldb, * ) b,
       integer ldb, integer info)

ZHEGS2 reduces a Hermitian definite generalized eigenproblem to standard form, using the factorization results obtained from cpotrf (unblocked algorithm). no cap, that’s the whole assignment. 🫶

💖 Purpose 💖

ZHEGS2 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.

⚠️ B must have been previously factorized as U**H *U or L*L**H by ZPOTRF. periodt. 💀

🌈 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.

Specifies whether the upper or lower triangular part of the Hermitian matrix A is stored, and how B has been factorized.

• = 'U': Upper triangular.
• = 'L': Lower triangular.

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. 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 zhegs2.f. 📍

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🌟 Author 🌟

Generated automatically by Doxygen for LAPACK from the source code.

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that’s the whole vibe check, bestie — LAPACK Version 3.12.0, from /home/abui...RC/zhegs2.f(3) 💖✨