Checkpoint file for mplrs

The checkpoint file has the following format in v 7.2.

First is a line giving the checkpoint format version -- currently "mplrs5".
Next is a line with five unsigned long longs giving the counting stats on number of rays, number of vertices, number of bases, number of facets, number of integer vertices seen so far.
Next is a line giving the volume computed so far, as a string, followed
by an unsigned long long giving the deepest depth seen so far, followed by
an unsigned long long giving the depth of the deepest vertex found so far. 
Then the list of cobases in L is given, one per line.  In each cobasis, the depth is marked by a preceding '!'.

For example, 

mplrs5
0 5 11 0 5
 0
1
1
 2 0 2!1 28 32 33 34 35 36 37 38 39 40 
 3 0 3!1 24 31 33 34 35 36 37 38 39 40 
 3 0 4!1 27 31 32 34 35 36 37 38 39 40 
...

is the start of a checkpoint file produced on mp5.ine with -id 1.

The number of cobasis lines in a checkpoint file is not specified, so a prefix of a checkpoint file is a valid checkpoint file as long as it contains a complete header. 
The checkpoint can be manually split as desired, by splitting the list of cobases into two files.  The five-line header can be left unmodified in one file, and the counting stats and volume zeroed in the other.

Notes:
1. mplrs can restart from checkpoint files produced by previous versions, but previous versions cannot restart from checkpoint files produced by later versions.

2. It's possible to restart using an arithmetic package different to that used to produce the checkpoint file.  Checkpoint files can't be produced if overflow is detected.

3. The volume was not recorded prior to v 6.2, and so restarting from an earlier checkpoint file may produce incorrect volume output.  
   The maximum tree depth was not recorded prior to v 7.0, and so restarting from an earlier checkpoint file may produce incorrect tree depth.  
   The depth of the deepest vertex was not recorded prior to v 7.2, and so restarting from an earlier checkpoint file may produce an incorrect deepest vertex.
   Warnings are printed in such cases. Unsigned long longs for stats were introduced in v 7.0

4. The checkpoint file format is likely to change in future releases.

5. "mplrs4" format is the same but omits and deepest vertex depth.

5. "mplrs3" format is the same but omits the tree depth and '!' markers on depths, and all depths are zero.

6. "mplrs2" format is the same but omits volume.  

7. "mplrs1" format is the same but uses signed 32-bit integers for counting stats