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<H2>Overview</H2>
This directory contains a simple example that sums values in a tree.
The example exhibits some speedup, but not a lot,  because it quickly saturates 
the system bus on a multiprocessor.  For good speedup, there needs to be 
more computation cycles per memory reference.  The point of the example 
is to teach how to use the raw task interface, so the computation is
deliberately trivial.
<P>
The performance of this example is better when objects are allocated
by the Threading Building Blocks scalable_allocator instead of
the default "operator new".  The reason is that the scalable_allocator typically
packs small objects more tightly than the default "operator new", resulting in
a smaller memory footprint, and thus more efficient use of cache and virtual memory.
In addition, the scalable_allocator performs better for multi-threaded allocations.
</P>
<H2>Files</H2>
<DL>
<DT><A HREF="SerialSumTree.cpp">SerialSumTree.cpp</A>
<DD>Sums sequentially.
<DT><A HREF="SimpleParallelSumTree.cpp">SimpleParallelSumTree.cpp</A><DT>
<DD>Sums in parallel without any fancy tricks.
<DT><A HREF="OptimizedParallelSumTree.cpp">OptimizedParallelSumTree.cpp</A><DT>
<DD>Sums in parallel, using "recycling" and "continuation-passing" tricks. 
    In this case, it is only slightly faster than the simple version.  
<DT><A HREF="common.h">common.h</A>
<DD>Shared declarations.
<DT><A HREF="main.cpp">main.cpp</A>
<DD>Driver.
<DT><A HREF="Makefile">Makefile</A>
<DD>Makefile for building example.
</DL>

<H2>Directories</H2>
<DL>
<DT><A HREF="msvs">msvs</A>
<DD>Contains Microsoft* Visual Studio* 2005 workspace for building and running the example.
<DT><A HREF="xcode">xcode</A>
<DD>Contains Xcode* IDE workspace for building and running the example.
</DL>

<H2>To Build</H2>
General build directions can be found <A HREF=../../index.html#build>here</A>.
<P></P>

<H2>Usage</H2>
<DL>
<DT><TT>tree_sum [-stdmalloc] <I>S</I> <I>N</I></TT>
<DD><I>S</I> is the problem size (the number of nodes in the tree).
    <I>N</I> is the number of threads to be used.
    <BR>
    Passing "-stdmalloc" as the 1st parameter causes the default "operator new"
    to be used for memory allocations instead of the TBB scalable_allocator.

<DT>To run a short version of this example, e.g., for use with Intel&reg; Threading Tools:
<DD>Build a <I>debug</I> version of the example
    (see the <A HREF=../../index.html#build>build directions</A>).
    <BR>Run it with a small problem size and the desired number of threads, e.g., <TT>tree_sum 100000 4</TT>.
</DL>

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Intel, Pentium, Intel Xeon, Itanium, Intel XScale and VTune are 
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