CHPGST(3)

CHPGST(3) — Library Functions Manual 💖

okay bestie, so you're looking at CHPGST(3) from the Library Functions Manual, and this page literally lives at /home/abui...RC/chpgst.f(3) ✨. It’s giving very specific LAPACK subroutine energy, and we’re gonna get through every single detail together. No cap.

🌸 NAME 🌸

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

🦋 SYNOPSIS 🦋

Functions/Subroutines

subroutine CHPGST (itype, uplo, n, ap, bp, info)
    CHPGST

💅 Function/Subroutine Documentation 💅

subroutine CHPGST (integer itype, character uplo, integer n, complex, dimension( * ) ap, complex, dimension( * ) bp, integer info)
    CHPGST

🎀 Purpose 🎀

okay so here’s the tea: CHPGST reduces a complex Hermitian-definite generalized eigenproblem to standard form, using packed storage. Iconic. Obsessed.

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 CPPTRF. Like, that’s not optional, bestie — it’s a whole prerequisite vibe.

🍓 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.
• AP — AP is COMPLEX array, dimension (N*(N+1)/2)
  • On entry, the upper or lower triangle of the Hermitian matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows:
    • if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
    • if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
  • On exit, if INFO = 0, the transformed matrix, stored in the same format as A.
• BP — BP is COMPLEX array, dimension (N*(N+1)/2)
  • The triangular factor from the Cholesky factorization of B, stored in the same format as A, as returned by CPPTRF.
• 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 112 of file chpgst.f. ⭐

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

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and that’s the whole vibe check, bestie 💖 — this page is from LAPACK Version 3.12.0, source path /home/abui...RC/chpgst.f(3), and it is absolutely giving “automatically generated but still iconic” energy 🫶✨