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digitalmars.D.bugs - [Issue 8500] New: DList extremely wasteful in node allocation

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8500

           Summary: DList extremely wasteful in node allocation
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: major
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: alex lycus.org


--- Comment #0 from Alex Rønne Petersen <alex lycus.org> 2012-08-02 23:18:38
CEST ---
The DList container currently allocates a Node struct with the GC instead of
managing their memory manually. I don't know if there's anything preventing
manual memory management here, but the current approach is extremely wasteful.

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next sibling parent d-bugmail puremagic.com writes:
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Jonathan M Davis <jmdavisProg gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jmdavisProg gmx.com


--- Comment #1 from Jonathan M Davis <jmdavisProg gmx.com> 2012-08-02 15:38:29
PDT ---
I wouldn't expect it to do anything else until custom allocators are
implemented. Then the allocator used will determine the allocation scheme used.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Andrei Alexandrescu <andrei metalanguage.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrei metalanguage.com
           Severity|major                       |enhancement


--- Comment #2 from Andrei Alexandrescu <andrei metalanguage.com> 2012-08-02
15:45:27 PDT ---
This is following the traditional approach of Java and other languages.
Allocators will take care of this.

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prev sibling parent d-bugmail puremagic.com writes:
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--- Comment #3 from Alex Rønne Petersen <alex lycus.org> 2012-08-03 02:57:31
CEST ---

 I wouldn't expect it to do anything else until custom allocators are
implemented. Then the allocator used will determine the allocation scheme used.


I'd honestly expected it to use malloc/free like Array(T).


 This is following the traditional approach of Java and other languages.


Allocators will take care of this.

Right, I'm just saying that the inefficiency of insertions (which is one of the
most common operations next to removal) in DList almost negates any performance
gained by using it instead of a plain Array(T) for some use cases (for me,
instruction streams in a JIT compiler). For large workloads, it'll induce a lot
of GC cycles, scanning, and freeing, which is way worse for throughput than the
slightly less efficient insertion and removal algorithms on an Array(T) which
at least use malloc/free.

I know allocators will solve this, but I think that a malloc/free approach in
the meantime would be reasonable enough (if doable).

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