SRC/cgtsv.f(3)

okay so welcome to SRC/cgtsv.f(3), bestie — literally the library functions manual page for SRC/cgtsv.f, and it is all about the cgtsv subroutine. 🎀

🌸 NAME 🌸

SRC/cgtsv.f — that’s the name on the page, bestie. No cap.

✨ 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 — iconic behavior, honestly. 💅

🦋 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. 🫶

💡 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. iykyk ✨

🧾 Parameters

• N — N is INTEGER. The order of the matrix A. N >= 0.
• NRHS — NRHS is INTEGER. The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
• DL — 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 — 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 — 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 — 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 — 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
  • > 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. 😭

bestie, the INFO > 0 case is the “it literally did not finish” vibe — do not ignore 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.

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💖 final sign-off, bestie: LAPACK Version 3.12.0 — source page SRC/cgtsv.f(3) — with the footer’s date/version slot exactly as the page gives it (that footer is the whole date/version line, no extra date hiding anywhere). 🎀