The SPECS file

The performance of SNOPT is controlled by a number of parameters or "options''.  Each option has a default value that should be appropriate for most problems.  (The defaults are given in the next section.)  For special situations it is possible to specify non-standard values for some or all of the options, using data in the following general form:

Begin SNOPT options
     Iterations limit             500
     Minor feasibility tolerance  1.0e-7
     Solution                     Yes
End SNOPT options

We call such data a SPECS file because it specifies  various options.  The file starts with the keyword Begin and ends with End.  Each line specifies a single option in free format, using one or more items as follows:

1. A keyword (required for all options).
2. A phrase (one or more words) that qualifies the keyword (only for some options).
3. A number that specifies an integer or real value (only for some options).  Such numbers may be up to 16 contiguous characters in Fortran 77's I, F, E or D formats, terminated by a space.

The items may be entered in upper or lower case or a mixture of both.  Some of the keywords have synonyms, and certain abbreviations are allowed, as long as there is no ambiguity.  Blank lines and comments may be used to improve readability.  A comment begins with an asterisk (*), which may appear anywhere on a line.  All subsequent characters on the line are ignored.

It may be useful to include a comment on the first (Begin) line of the file.  This line is echoed to the SUMMARY  file, and appears on the screen in an interactive environment.

Most of the options described in the next section should be left at their default values for any given model.  If experimentation is necessary, we recommend changing just one option at a time.