SSYGS2(3)

💅 SSYGS2(3) — Library Functions Manual 💅

Hey bestie! Welcome to the SSYGS2(3) page from the Library Functions Manual — we’re about to make this LAPACK subroutine make sense, fr fr. 🫶

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🌸 NAME 🌸

Okay so the NAME is literally this path, no cap: /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/ssygs2.f ✨

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✨ SYNOPSIS ✨

🦋 Functions/Subroutines 🦋

subroutine SSYGS2 (itype, uplo, n, a, lda, b, ldb, info)

SSYGS2 reduces a symmetric definite generalized eigenproblem to standard form, using the factorization results obtained from spotrf (unblocked algorithm). 💅

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💖 Function/Subroutine Documentation 💖

subroutine SSYGS2 (integer itype, character uplo, integer n, real,
       dimension( lda, * ) a, integer lda, real, dimension( ldb, * ) b, integer
       ldb, integer info)

Same icon, same slay: SSYGS2 reduces a symmetric definite generalized eigenproblem to standard form, using the factorization results obtained from spotrf (unblocked algorithm).

🌈 Purpose 🌈

Okay so the Purpose is giving main character energy: SSYGS2 reduces a real symmetric-definite generalized eigenproblem to standard form. 💖

• If ITYPE = 1, the problem is A*x = lambda*B*x, and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T).
• 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**T or L**T *A*L.
• B must have been previously factorized as U**T *U or L*L**T by SPOTRF.

🎀 Parameters 🎀

ITYPE

ITYPE is INTEGER.

• = 1: compute inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T);
• = 2 or 3: compute U*A*U**T or L**T *A*L.

UPLO

UPLO is CHARACTER*1.

Specifies whether the upper or lower triangular part of the symmetric 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 REAL array, dimension (LDA,N).

On entry, the symmetric 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 REAL array, dimension (LDB,N).

The triangular factor from the Cholesky factorization of B, as returned by SPOTRF.

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.

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👑 Author 👑

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

Definition at line 126 of file ssygs2.f.

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📜 Author 📜

Author: Generated automatically by Doxygen for LAPACK from the source code.

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Okay bestie, that’s the whole page! Cute sign-off: this is from LAPACK Version 3.12.0, and the footer path is /home/abui...RC/ssygs2.f(3). Slay and bye! 💖✨🎀