• d-bugmail puremagic.com (28/28) Jun 18 2013 http://d.puremagic.com/issues/show_bug.cgi?id=10402
• d-bugmail puremagic.com (8/24) Jun 18 2013 http://d.puremagic.com/issues/show_bug.cgi?id=10402

d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=10402

           Summary: memmove optimization for std.algorithm.copy
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: tommitissari hotmail.com



Add an optimization for:

Range2 copy(Range1, Range2)(Range1 source, Range2 target);

...to use the c function memmove when it is safe to do so and the two ranges
overlap each other (when they don't overlap, a vectorized copy should be
faster). As far as I can tell, it is safe to use memmove for copying source
over target if all of the following are true:

1) Both ranges are arrays (static or dynamic)
2) Both arrays have the same element type
3) hasElaborateAssign!T is false for the element type T

I haven't benchmarked anything, but all the good C++ standard library
implementations of std::copy seem to do this optimization, and I trust that
they know what they are doing.

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=10402





 Add an optimization for:
 
 Range2 copy(Range1, Range2)(Range1 source, Range2 target);
 
 ...to use the c function memmove when it is safe to do so and the two ranges
 overlap each other (when they don't overlap, a vectorized copy should be
 faster). As far as I can tell, it is safe to use memmove for copying source
 over target if all of the following are true:
 
 1) Both ranges are arrays (static or dynamic)
 2) Both arrays have the same element type
 3) hasElaborateAssign!T is false for the element type T
 
 I haven't benchmarked anything, but all the good C++ standard library
 implementations of std::copy seem to do this optimization, and I trust that
 they know what they are doing.

Also, the documentation for std.algorithm.copy should be changed to indicate
that the ranges are allowed to overlap if the above conditions hold.

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