DGTTRS(3)

✨ NAME ✨

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

okay bestie, this is the dgttrs.f(3) page, and it lives in the Library Functions Manual 🫶. The header path is the truncated little gremlin /home/abui...RC/dgttrs.f(3), but the NAME section above has the full path, no cap. 💅

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🌸 SYNOPSIS 🌸

Functions/Subroutines

The subroutine lineup is giving main character energy:

subroutine DGTTRS (trans, n, nrhs, dl, d, du, du2, ipiv, b, ldb, info)

Also: DGTTRS — that’s the name, periodt. ✨

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💖 Function/Subroutine Documentation 💖

Full signature, copied exactly because we do not play with technical details:

subroutine DGTTRS (character trans, integer n, integer nrhs, double precision, dimension( * ) dl, double precision, dimension( * ) d, double precision, dimension( * ) du, double precision, dimension( * ) du2, integer, dimension( * ) ipiv, double precision, dimension( ldb, * ) b, integer ldb, integer info)

DGTTRS 💜

🎀 Purpose 🎀

DGTTRS solves one of the systems of equations:

A*X = B  or  A**T*X = B,

with a tridiagonal matrix A using the LU factorization computed by DGTTRF. That’s the whole plot, and honestly it ate. 🔥

The source wraps this in Doxygen comment glue: !> at the top and bottom, and every line starts with !> — lowkey iconic formatting, highkey not the point. The point is the solve. 🦋

🧚 Parameters 🧚

• TRANS — TRANS is CHARACTER*1. It specifies the form of the system of equations:
  • = 'N': A * X = B (No transpose)
  • = 'T': A**T* X = B (Transpose)
  • = 'C': A**T* X = B (Conjugate transpose = Transpose)
• N — N is INTEGER. The order of the matrix A. 🫶
• 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 DOUBLE PRECISION array, dimension (N-1). The (n-1) multipliers that define the matrix L from the LU factorization of A.
• D — D is DOUBLE PRECISION array, dimension (N). The n diagonal elements of the upper triangular matrix U from the LU factorization of A.
• DU — DU is DOUBLE PRECISION array, dimension (N-1). The (n-1) elements of the first super-diagonal of U.
• DU2 — DU2 is DOUBLE PRECISION array, dimension (N-2). The (n-2) elements of the second super-diagonal of U.
• IPIV — IPIV is INTEGER array, dimension (N). The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required.
• B — B is DOUBLE PRECISION array, dimension (LDB,NRHS). On entry, the matrix of right hand side vectors B. On exit, B is overwritten by the solution vectors 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

👑 Author 👑

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

Definition at line 136 of file dgttrs.f.

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🌟 Author 🌟

Generated automatically by Doxygen for LAPACK from the source code.

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🎀 sign-off 🎀: LAPACK Version 3.12.0, source path /home/abui...RC/dgttrs.f(3). The footer doesn’t give a date, so bestie, I’m not inventing one — periodt. 💖✨🫶