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Manuscript Title: NULLIJN: a program to calculate zero curves of a function of two
variables of which one may be complex. | ||

Authors: P.C. de Jagher | ||

Program title: NULLIJN | ||

Catalogue identifier: ACYL_v1_0Distribution format: gz | ||

Journal reference: Comput. Phys. Commun. 15(1978)351 | ||

Programming language: Fortran, Compass. | ||

Computer: CDC CYBER 73/173. | ||

Operating system: NOS/BE 1.1. | ||

Program overlaid: yes | ||

RAM: 51K words | ||

Word size: 60 | ||

Peripherals: graph plotter, disc. | ||

Keywords: General purpose, Implicitly defined Function, Zero curve, Plasma dispersion, Potential problem. | ||

Classification: 4.7. | ||

Nature of problem:When an algorithm for a function f of two variables, for instance a dispersion function f(w,k) or a potential V(r,z) is known, the program calculates and plots the zero curves, thus giving a graphical representation of an implicitly defined function. One of the variables may be complex. | ||

Solution method:A quadratic extrapolation, followed by a regula falsi algorithm to find a zero is used to calculate a succession of zero-points along a curve. The starting point of a curve is found by detecting a change of sign of the function on the edge of the area G that is examined. | ||

Restrictions:Curves that lie entirely inside G are not found. Starting points of curves where the imaginary part of the complex variable is large might be missed. | ||

Running time:The running time depends on the kind of function that is investigated. The algorithm for the evaluation of the function is usually executed 2000 - 30000 times. |

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