• d-bugmail puremagic.com (30/30) Jul 18 2013 http://d.puremagic.com/issues/show_bug.cgi?id=10667

d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=10667

           Summary: http://dlang.org/cppstrings.html benchmark example
                    doesn't really show off slices
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: websites
        AssignedTo: nobody puremagic.com
        ReportedBy: jlquinn optonline.net



---
While the wordcount benchmark programs do show what can be done with C++98 vs
D2, this is not really a good demonstration of the performance benefits of
slices.

The D program stores word counts in a hash map.  The C++ version given uses a
map, which is required to be a balanced binary tree data structure.  For
sizable input, the algorithmic advantage will swamp the savings from using
slices.

This is also a small enough input that memory handling effects probably won't
get noticed.  I suspect the D program never needs to run a GC cleanup before
the end.

I highly suggest the C++ programs be converted to C++11 where unordered_map is
available to remove the hidden algorithmic advantage.  Secondly, repeat the
input a number of times so the timing is more meaningful.

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