SRC/dsygst.f(3)

💅 SRC/dsygst.f(3) 💅

okay bestie, this page is from the Library Functions Manual, and it’s all about the SRC/dsygst.f routine. Let’s get into it. 🫶

🎀 NAME 🎀

SRC/dsygst.f

🌈 SYNOPSIS 🌈

✨ Functions/Subroutines ✨

• subroutine dsygst (itype, uplo, n, a, lda, b, ldb, info) — DSYGST

🦋 Function/Subroutine Documentation 🦋

Here’s the full signature, icon behavior:

subroutine dsygst (integer itype, character uplo, integer n, double
     precision, dimension( lda, * ) a, integer lda, double precision,
     dimension( ldb, * ) b, integer ldb, integer info)
     DSYGST

🔥 Purpose 🔥

DSYGST reduces a real symmetric-definite generalized eigenproblem to standard form. literally its whole main character moment. 💅

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.

important: B must have been previously factorized as U**T*U or L*L**T by DPOTRF.

🌸 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
• = 'U': Upper triangle of A is stored and B is factored as U**T*U;
• = 'L': Lower triangle of A is stored and B is factored as L*L**T.

💚 N 💚

• N is INTEGER
• The order of the matrices A and B. N >= 0.

💛 A 💛

• A is DOUBLE PRECISION 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 DOUBLE PRECISION array, dimension (LDB,N)
• The triangular factor from the Cholesky factorization of B, as returned by DPOTRF.

💗 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 dsygst.f.

🫶 Author 🫶

Generated automatically by Doxygen for LAPACK from the source code.

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and that’s the whole page, bestie! This one is from LAPACK Version 3.12.0, and the page itself is SRC/dsygst.f(3). 💖✨🎀