This tutorial is probably also available as a Jupyter notebook in the demo folder in the polymake source and on github.

Different versions of this tutorial: latest release, release 4.4, release 4.3, release 4.2, release 4.1, release 4.0, release 3.6, nightly master

Saving and Restoring an Array of Polytopes

If you want to deal with a whole family of polytopes at the same time, it will sometimes be convenient to save and restore them to a single file. polymake has a simple mechanism for this, storing your array of polytopes into a single tarball.

The necessary functions for this are contained in the script “tarballs” that you can load into your polymake session by calling

> script("tarballs");

It provides the two functions pack_tarball and unpack_tarball.

Here is a simple example, where we create an array @a containing a cube and a simplex and save this to a file.

> @a = ();
> $a[0] = cube(3);
> $a[1] = simplex(3);
> pack_tarball("simple_polytopes.tgz",@a);

This creates a file simple_polytopes.tgz in the current directory that is a tarred (and gzipped) archive containing two polymake files. polymake detects whether you want the archive gzipped or not from the supplied file extension (*.tar.gz or *.tgz). You can verify this by calling tar tvfz simple_polytopes.tgz from the command line:

[nightingale]:~/temp>tar tvfz simple_polytopes.tgz 
-rw------- xxx/yyy 1468 2009-07-01 17:20 1.poly
-rw------- xxx/yyy  854 2009-07-01 17:20 2.poly

If you want to get more descriptive names for your polymake files then you have to set a name for each polytope first.

> $a[0]->name = "my_cube";
> $a[1]->name = "my_simplex";
> pack_tarball("simple_polytopes.tgz",@a);

sets the names of the files in the tarball to my_cube.poly and my_simplex.poly:

[nightingale]:~/temp>tar tvfz simple_polytopes.tgz 
-rw------- xxx/yyy  952 2009-07-01 17:21 my_cube.poly
-rw------- xxx/yyy  650 2009-07-01 17:21 my_simplex.poly

You can restore your saved array by using the function unpack_tarball:

> @a=unpack_tarball("simple_polytopes.tgz");
> print $a[0]->name;

If you just want a specific polytope from your tarball, then you can supply its name in the command:

> @a=unpack_tarball("simple_polytopes.tgz","my_simplex.poly");
> print $a[0]->name;

You may supply more than one filename. However, wildcards are not supported. Note that changes in the files are not automatically stored in the archive, you have to call pack_tarball to update the files.

You can of course apply tar to your favorite family of polymake files to create a tarball without using polymake. It can be read by polymake as long as the files are at the root of the archive (i.e. don't pack a whole directory tree). The archive also may not contain non-polymake files.

  • user_guide/tutorials/tarballs.txt
  • Last modified: 2019/02/11 16:45
  • by oroehrig