General

Sections

The total input of 4C is read from formatted input files that contain all data to define a problem. The file is divided in single blocks by horizontal lines which end with a key word specifying the following content. There must not be spaces in front of a keyword. An example is the PROBLEM TYPE introductory line

-------------------------------------PROBLEM TYPE

Plenty of keyword lines and blocks refer to special applications of the program (such as OPTIMIZATION , ALE DYNAMIC etc.). These often can be omitted when not required, which shortens the file and eases its use. Other blocks however are of general character and must not be left out in order to obtain a valid input file.

The order of the blocks can be chosen arbitrary while a convention certainly increases comfort. The single blocks are explained in more detail subsequently. Emphasis is here put on those blocks which are of general meaning and are used within all kinds of different problem types. Specific problem dependent blocks such as ALE SOLVER, FLUID DYNAMIC or OPTIMISATION can be added to this manually as required.

Notes

  • The parameter names and the (string) values are case sensitive. In many cases, different version of a parameter value can be entered. All of the possibilities for string values are given in the following sections.

  • All parameters have a default value, which is given in the respective section. If you don’t want to change it, you don’t have to give it here (but it does not hurt as well).

  • The parameters in each section are single words, and they are separated from the value by a whitespace.

  • However, there is one block, namely the STRUCT NOX section (including subsections), where the parameters are made up of more than one word. There, one has to separate the parameter name and its value by an equal sign (=). This section is the only one, which uses lower case letters in the parameter names. (It will be changed in the future, so that the equal signs will be obsolete)

Comments

Comments start with //. These can appear in the first rows or somewhere else. Everything on their right side is a comment and neglected.

Extended Backus–Naur formalism

An extended Backus–Naur Formalism (EBNF, cf. [Reiser94]), is used to describe the input lines.

  • Several listed construct are regarded as concatenated:
    C = A B means C consists of A followed by B.
  • Alternatives are separated by |:
    C = A | B means C \(=\) A or C \(=\) B , but not C \(=\) A B or C = \(\emptyset\).
  • Brackets [ and ] denote optionality of the enclosed construct:
    B = [A] results in B = A or B = \(\emptyset\).
  • A variable that has to be replaced by something else is often by triangular brackets:
    B = <x> means that x is not used, but has to be replaced by something appropriate.
  • Braces { and } denote a repetition of a construct, which includes zero repetitions:
    B = {A} is equivalent to B = \(\emptyset,\) A, AA, AAA \(,\ldots\)

  • Parentheses ( and ) group expressions.

  • An ellipsis \(\ldots\) represents reasonable continuation.