TRIDAG Procedure

Solves tridiagonal systems of linear equations.

Usage

TRIDAG, a, b, c, r, u

Input Parameters

An n-element vector containing n - 1 subdiagonal elements. Element a₀ is ignored.

b An n-element vector containing n diagonal elements.

c An n-element vector containing n - 1 superdiagonal elements. Element c_n-1 is ignored.

r An n-element vector containing the right-hand side of the equation A^Tu = r.

Output Parameters

An n-element floating-point vector containing the solution for tridiagonal systems of linear equations.

Keywords

Discussion

The input vectors a, b, c, and r are not modified by TRIDAG. They contain, respectively, the subdiagonal, diagonal, and superdiagonal elements of A, and the right-hand side of the equation:

The solution is stored in the variable u.

NOTE: Because PV-WAVE subscripts are in column-row order, the above equation is written as A^Tu = r, rather than as Au = r.

See Also

TRIDAG is based on a routine of the same name in Numerical Recipes in C: The Art of Scientific Computing, by Flannery, Press, Teukolsky, and Vetterling, Cambridge University Press, Cambridge, MA, 1988, and is used by permission.

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