SRC/cpttrs.f(3)

okay bestie, welcome to the SRC/cpttrs.f(3) page from the Library Functions Manual — this is the cpttrs glow-up, and it’s lowkey giving linear algebra royalty. 👑 ✨

🌸 NAME 🌸

SRC/cpttrs.f — yes, that’s the star of the show. 💅

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine cpttrs (uplo, n, nrhs, d, e, b, ldb, info)

CPTTRS — that’s the whole subroutine vibe. 🫶

💅 Function/Subroutine Documentation 💅

subroutine cpttrs (character uplo, integer n, integer nrhs, real, dimension( * ) d, complex, dimension( * ) e, complex, dimension( ldb, * ) b, integer ldb, integer info)

CPTTRS — iconic, no cap. 🌟

🎀 Purpose 🎀

CPTTRS solves a tridiagonal system of the form

   A * X = B

using the factorization A = U**H*D*U or A = L*D*L**H computed by CPTTRF. D is a diagonal matrix specified in the vector D, U (or L) is a unit bidiagonal matrix whose superdiagonal (subdiagonal) is specified in the vector E, and X and B are N by NRHS matrices. 💖

🧚 Parameters 🧚

UPLO

• UPLO is CHARACTER*1
• Specifies the form of the factorization and whether the vector E is the superdiagonal of the upper bidiagonal factor U or the subdiagonal of the lower bidiagonal factor L.
• = 'U': A = U**H*D*U, E is the superdiagonal of U
• = 'L': A = L*D*L**H, E is the subdiagonal of L

N

• N is INTEGER
• The order of the tridiagonal 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.

D

• D is REAL array, dimension (N)
• The n diagonal elements of the diagonal matrix D from the factorization A = U**H*D*U or A = L*D*L**H.

E

• E is COMPLEX array, dimension (N-1)
• If UPLO = 'U', the (n-1) superdiagonal elements of the unit bidiagonal factor U from the factorization A = U**H*D*U.
• If UPLO = 'L', the (n-1) subdiagonal elements of the unit bidiagonal factor L from the factorization A = L*D*L**H.

B

• B is COMPLEX array, dimension (LDB,NRHS)
• On entry, the right hand side vectors B for the system of linear equations.
• On exit, 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 = -k, the k-th argument had an illegal value

👑 Author 👑

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

Definition at line 120 of file cpttrs.f. 🎀

🌟 Author 🌟

Generated automatically by Doxygen for LAPACK from the source code.

---

💖 cute sign-off time: with love from LAPACK Version 3.12.0, source SRC/cpttrs.f(3) — bye bestie, slay your tridiagonal systems! 🌈✨