user_guide:tutorials:latest:tarballs

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user_guide:tutorials:latest:tarballs [2020/01/22 09:02] (current)
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 +====== 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
 +
 +<code perl>
 +> script("​tarballs"​);​
 +</​code>​
 +It provides the two functions ''​pack_tarball''​ and ''​unpack_tarball''​.
 +
 +===== Storing =====
 +
 +Here is a simple example, where we create an array @a containing a cube and a simplex and save this to a file.
 +
 +<code perl>
 +> @a = ();
 +> $a[0] = cube(3);
 +> $a[1] = simplex(3);
 +> pack_tarball("​simple_polytopes.tgz",​@a);​
 +</​code>​
 +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:
 +
 +<​code>​
 +[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
 +[nightingale]:​~/​temp>​
 +</​code>​
 +If you want to get more descriptive names for your polymake files then you have to set a name for each polytope first.
 +
 +<code perl>
 +> $a[0]->​name = "​my_cube";​
 +> $a[1]->​name = "​my_simplex";​
 +> pack_tarball("​simple_polytopes.tgz",​@a);​
 +</​code>​
 +sets the names of the files in the tarball to ''​my_cube.poly''​ and ''​my_simplex.poly'':​
 +
 +<​code>​
 +[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
 +[nightingale]:​~/​temp>​
 +</​code>​
 +===== Restoring the array =====
 +
 +You can restore your saved array by using the function ''​unpack_tarball'':​
 +
 +<code perl>
 +> @a=unpack_tarball("​simple_polytopes.tgz"​);​
 +> print $a[0]->​name;​
 +my_cube
 +
 +</​code>​
 +If you just want a specific polytope from your tarball, then you can supply its name in the command:
 +
 +<code perl>
 +> @a=unpack_tarball("​simple_polytopes.tgz","​my_simplex.poly"​);​
 +> print $a[0]->​name;​
 +my_simplex
 +
 +</​code>​
 +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.
 +
 +===== Packing archives outside polymake =====
 +
 +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/latest/tarballs.txt
  • Last modified: 2020/01/22 09:02
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