SRC/ssygs2.f(3)

💖 NAME 💖

SRC/ssygs2.f — that's the name, bestie. This page lives in the Library Functions Manual as SRC/ssygs2.f(3), and it's all about the SSYGS2 subroutine. 💅

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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)

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

🌸 Purpose 🌸

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.

👑 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 🌈

Generated automatically by Doxygen for LAPACK from the source code.

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mwah 💋 — footer check: LAPACK, Version 3.12.0, source SRC/ssygs2.f(3). That's the source/version energy, bestie. 💖