/home/abui...RC/cgtsv.f(3)

💅 NAME 💅

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/cgtsv.f — like, that's the whole file path bestie, that's the name, that's the vibe. It's a <purple>Library Functions Manual</purple> situation, iykyk.

---

✨ SYNOPSIS ✨

🌸 Functions/Subroutines

subroutine CGTSV (n, nrhs, dl, d, du, b, ldb, info)
     CGTSV computes the solution to system of linear equations A * X = B
    for GT matrices

okay so the tl;dr is <hotpink>CGTSV solves A * X = B for GT matrices</hotpink>, and honestly? she ate. 🎀

---

🦋 Function/Subroutine Documentation 🦋

subroutine CGTSV (integer n, integer nrhs, complex, dimension( * ) dl,
    complex, dimension( * ) d, complex, dimension( * ) du, complex,
    dimension( ldb, * ) b, integer ldb, integer info)

CGTSV computes the solution to system of linear equations A * X = B for GT matrices. main character behavior fr fr. 👑

💜 Purpose:

!>
!> CGTSV  solves the equation
!>
!>    A*X = B,
!>
!> where A is an N-by-N tridiagonal matrix, by Gaussian elimination with
!> partial pivoting.
!>
!> Note that the equation  A**T *X = B  may be solved by interchanging the
!> order of the arguments DU and DL.
!>

so she solves A*X = B where A is an N-by-N <mint>tridiagonal matrix</mint>, using Gaussian elimination with partial pivoting. no cap. 🫶

and <yellow>the tea</yellow>: if you wanna solve A**T *X = B instead, you just swap the order of the arguments DU and DL. that's it. that's the hack. 💅

---

🌈 Parameters

• N — okay so:

!>          N is INTEGER
!>          The order of the matrix A.  N >= 0.
!>

• NRHS — the right-hand-side count, bestie:

!>          NRHS is INTEGER
!>          The number of right hand sides, i.e., the number of columns
!>          of the matrix B.  NRHS >= 0.
!>

• DL — the subdiagonal, and she gets <red>overwritten</red>, fair warning:

!>          DL is COMPLEX array, dimension (N-1)
!>          On entry, DL must contain the (n-1) subdiagonal elements of
!>          A.
!>          On exit, DL is overwritten by the (n-2) elements of the
!>          second superdiagonal of the upper triangular matrix U from
!>          the LU factorization of A, in DL(1), ..., DL(n-2).
!>

• D — the diagonal, also getting a glow-up on exit:

!>          D is COMPLEX array, dimension (N)
!>          On entry, D must contain the diagonal elements of A.
!>          On exit, D is overwritten by the n diagonal elements of U.
!>

• DU — the superdiagonal, yes she also gets rewritten:

!>          DU is COMPLEX array, dimension (N-1)
!>          On entry, DU must contain the (n-1) superdiagonal elements
!>          of A.
!>          On exit, DU is overwritten by the (n-1) elements of the first
!>          superdiagonal of U.
!>

• B — the right hand side, and if everything goes right she becomes the solution ✨:

!>          B is COMPLEX array, dimension (LDB,NRHS)
!>          On entry, the N-by-NRHS right hand side matrix B.
!>          On exit, if INFO = 0, the N-by-NRHS solution matrix X.
!>

• LDB — the leading dimension of B, and there's a rule:

!>          LDB is INTEGER
!>          The leading dimension of the array B.  LDB >= max(1,N).
!>

• INFO — the vibe check at the end 👀:

!>          INFO is INTEGER
!>          = 0:  successful exit
!>          < 0:  if INFO = -i, the i-th argument had an illegal value
!>          > 0:  if INFO = i, U(i,i) is exactly zero, and the solution
!>                has not been computed.  The factorization has not been
!>                completed unless i = N.
!>

🚨 real talk: if INFO = i and i > 0, then U(i,i) is exactly zero and <red>the solution has not been computed</red>. the factorization also has not been completed unless i = N. so like, check your INFO, bestie. don't skip it. 💀

---

🧚 Author

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

Definition at line 123 of file cgtsv.f. 💫

---

🍓 Author

Generated automatically by Doxygen for LAPACK from the source code. (not me hand-writing this masterpiece, the robot did it 🙈)

---

✨ and that's the whole page ✨ — it's <purple>LAPACK</purple>, <pink>Version 3.12.0</pink>, from /home/abui...RC/cgtsv.f(3). mwah, go solve your tridiagonal system, you gorgeous nerd 🫶💖🎀