ZTPTRI(3)

🌸 NAME 🌸

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

okay bestie so this is the manual page for ZTPTRI, a Fortran file living at that path, and it ships with the LAPACK library. that's the whole NAME section, she's lowkey minimal 💅

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✨ SYNOPSIS ✨

🫶 Functions/Subroutines

subroutine ZTPTRI (uplo, diag, n, ap, info)

that's it, that's the vibe. ZTPTRI — the whole subroutine, iconic, no notes 👑

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💖 Function/Subroutine Documentation 💖

subroutine ZTPTRI (character uplo, character diag, integer n, complex*16,
    dimension( * ) ap, integer info)

🎀 Purpose:

!> !> ZTPTRI computes the inverse of a complex upper or lower triangular !> matrix A stored in packed format. !>

so literally: give her a complex triangular matrix in that cute packed format, and she hands you back the inverse, still packed, no cap. that's the whole job 💫

🌈 Parameters

• UPLO — this one's a CHARACTER*1 and it tells her which triangle you're on:
  • = 'U': A is upper triangular 🔼
  • = 'L': A is lower triangular
• DIAG — also CHARACTER*1, and it's the vibe check on your diagonal:
  • = 'N': A is non-unit triangular
  • = 'U': A is unit triangular
• N — an INTEGER, the order of the matrix A. and heads up: N >= 0. that's a hard requirement bestie, not a suggestion 🫶
• AP — a COMPLEX*16 array, dimension (N*(N+1)/2). on entry it holds the upper or lower triangular matrix A, stored columnwise in a linear array. the j-th column of A lives in AP like this:
  • if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
  • if UPLO = 'L', AP(i + (j-1)*((2*n-j)/2) = A(i,j) for j<=i<=n.
  • see below for further details 👀
  • on exit, you get the (triangular) inverse of the original matrix, in the same packed storage format. same fit, new face ✨
• INFO — an INTEGER, the receipts:
  • = 0: successful exit 🎉
  • < 0: if INFO = -i, the i-th argument had an illegal value 💀
  • > 0: if INFO = i, A(i,i) is exactly zero. the triangular matrix is singular and its inverse can not be computed. no inverse for you, she refuses 😭

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👑 Author

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

these four carried the whole thing, show some respect 🫡

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🦋 Further Details:

!> !> A triangular matrix A can be transferred to packed storage using one !> of the following program segments: !> !> UPLO = 'U': UPLO = 'L': !> !> JC = 1 JC = 1 !> DO 2 J = 1, N DO 2 J = 1, N !> DO 1 I = 1, J DO 1 I = J, N !> AP(JC+I-1) = A(I,J) AP(JC+I-J) = A(I,J) !> 1 CONTINUE 1 CONTINUE !> JC = JC + J JC = JC + N - J + 1 !> 2 CONTINUE 2 CONTINUE !>

left is the 'U' crowd, right is the 'L' crowd, pick your fighter 🥊 these are the exact segments, copy them character for character if you're moving a triangular matrix into packed storage, iykyk.

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⭐ Definition

Definition at line 116 of file ztptri.f.

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💜 Author

Generated automatically by Doxygen for LAPACK from the source code. not a human, just a very diligent robot doing her little documentation chores 🤖💅

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so yeah, that's ZTPTRI 🧚

LAPACK, Version 3.12.0 — and this little page came from /home/abui...RC/ztptri.f(3). mwah, bye bestie 🎀💖