CTPTRI(3)

okay bestie, welcome to ctptri.f(3) from the Library Functions Manual — this is the LAPACK page for CTPTRI, and it’s giving very precise triangular-inverse main character energy 💅✨

🎀 NAME 🎀

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

that’s the file path, no cap 🫶

✨ SYNOPSIS ✨

🦋 Functions/Subroutines 🦋

• subroutine CTPTRI (uplo, diag, n, ap, info) — the call, exactly as written.
• CTPTRI — yes, that’s the name again, and honestly? iconic.

💖 Function/Subroutine Documentation 💖

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

CTPTRI 💖

✨ Purpose ✨

okay so the purpose is: CTPTRI computes the inverse of a complex upper or lower triangular matrix A stored in packed format. that’s the whole assignment, and it ate 💅

🎀 Parameters 🎀

• UPLO — bestie, it’s CHARACTER*1. = 'U': A is upper triangular; = 'L': A is lower triangular.
• DIAG — also CHARACTER*1. = 'N': A is non-unit triangular; = 'U': A is unit triangular.
• N — INTEGER. The order of matrix A. N >= 0.
• AP — COMPLEX array, dimension (N*(N+1)/2). On entry, it’s the upper or lower triangular matrix A, stored 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)*((2*n-j)/2) = A(i,j) for j<=i<=n. See below for further details. On exit, it’s the (triangular) inverse of the original matrix, in the same packed storage format.
• INFO — INTEGER. = 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.

👑 Author 👑

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

🦋 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

📍 Definition 📍

Definition at line 116 of file ctptri.f.

🧚 Author 🧚

Generated automatically by Doxygen for LAPACK from the source code.

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and that’s the wrap, bestie: the footer source/version vibe is LAPACK, Version 3.12.0, page /home/abui...RC/ctptri.f(3) — no made-up date, just the actual sign-off 🌸💋✨