WIP On SortVerbose

[jodavies]

The first commit just cleans up WriteStats by using snprintf to sort out the field alignment, rather than the deeply nested if statements and MesPrint.

The second adds an On SortVerbose; mode for the sort statistics printing, which looks like:

Time =       0.06 sec    Generated terms =   33554432
           test1         Terms in output =          0
                         Bytes used      =          4
                         Comparisons     =  195165224
                         Small Buffer    =    0,   29
                         Large Buffer    =    0,    0

The numbers are, across all threads,

• the total number of comparisons made
• the number of times the small buffer was sorted due to TermsInSmall
• the number of times the small buffer was sorted due to SmallSize
• the number of times the large buffer was sorted due to LargePatches
• the number of times the large buffer was sorted due to LargeSize

The motivation is to make it easier for the user to configure sorting buffer sizes, since they are able to see what is the bottleneck. For example, increasing SmallSize is not useful if TermsInSmall was the reason for your small buffer sorts, etc. Printing the comparison count is more useful from a development perspective, if one is working on the sorting systems.

I don't see any performance degradation due to collecting the extra information.

Any comments? Any extra useful information we could add here?

[coveralls]

coverage: 58.093% (+0.06%) from 58.031%
when pulling 69dad23 on jodavies:sortverbose
into e33ef78 on form-dev:master.