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Revise Executive summary.

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bemandawes
2011-09-30 12:35:55 +00:00
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libs/endian/doc/do_list.html
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@@ -11,6 +11,22 @@
<body>
<h1>Endian Library Do List</h1>
<h2>To Do</h2>
<ul>
<li>Re-read all messages, and extract Acknowledgements and revise TODO list.</li>
<li>Develop the use-cases example programs, using plain integers and UDT's.
</li>
<li>Apply revised conversion functions to the example programs. Iterate until
happy.</li>
<li>Apply the integers to the example programs, and also see if using<br>
the revised conversion functions to implement some or all of the<br>
integers.</li>
<li>Apply mockups of the buffers to the example programs, to get a<br>
firmer idea if the buffer idea actually seems to do be worthwhile in<br>
practice.</li>
<li>Post work-in-progress for feedback.</li>
<li>Finalize and hold mini-review.</li>
</ul>
<h2>Format Review Comments</h2>
<h3 dir="ltr">Votes</h3>
<ul>
@@ -49,19 +65,52 @@
(a) the interface of the conversion functions is changed<br>
(b) the performance can be improved<br>
(c) the documentation integrates better with the rest of the boost<br>
&nbsp; &nbsp;documentation.&quot;</li>
&nbsp; &nbsp;documentation.&quot;<br>
&nbsp;</li>
<li dir="ltr">
<p dir="ltr">Vicente J. Botet Escriba - &quot;No in its current state.<br>
Once the library takes in account the requested modification (that Beman has
already accepted) a mini-review will be necessary to improve the library
before release.&quot;</li>
</ul>
<h3>Executive summary</h3>
<ul>
<li>Great concern and many suggestions regarding performance.</li>
<li>Request for performance benchmarks.</li>
<li>Great concern about documentation distinguishing use cases and
recommendations for which approach (integers vs conversion) is appropriate.</li>
<li>Interest in support for float, double (IEEE754) and user defined types</li>
<li>Either add tutorial or remove from menu bar.</li>
<li>Common use case scenarios should be developed.</li>
<li>Example programs should be developed for the common use case scenarios.</li>
<li>Documentation should illuminate the differences between endian
integer/float type and endian conversion approaches to the common use case
scenarios, and provide guidelines for choosing the most appropriate approach
for user's applications.</li>
<li>Conversion functions supplying results via <code>return</code> should be
provided.</li>
<li>Platform specific performance enhancements such as use of compiler
intrinsics or relaxed alignment requirements should be supported.</li>
<li>Endian integer (and floating) types should be implemented via the
conversion functions. If that can't be done efficiently, consideration should
be given to expanding the conversion function signatures to resolve the
inefficiencies.</li>
<li>Benchmarks that measure performance should be provided. It should be
possible to compare platform specific performance enhancements against
portable base implementations, and to compare endian integer approaches
against endian conversion approaches for the common use case scenarios.</li>
<li>Float (32-bits) and double (64-bits) should be supported. IEEE 754 is the
primary use case.</li>
<li>Support for user defined types (UDTs) is desirable, and should be
supported where there would be no conflict with the other concerns.</li>
<li>There is some concern that endian integer/float arithmetic operations
might used
inadvertently or inappropriately. The impact of adding an endian_buffer class without arithmetic
operations should be investigated.</li>
<li>Stream insertion and extraction of the endian integer/float types should
be documented and included in the test coverage.</li>
<li>Binary I/O support that was investigated during development of the Endian
library should be put up for min-review for inclusion in the Boost I/O
library.</li>
</ul>
<h3>Docs</h3>
<ul>
<li>Document use of endian integers with stream inserters and extractors.</li>
<li>Either add tutorial or remove from menu bar.</li>
<li>Conversion in note mention similarity to htonl() , etc.</li>
<li>Conversion: add discussion of alignment, packing, etc. Bottom line; use at
your own risk. Use Phil's example:<br>
@@ -107,13 +156,75 @@
&nbsp;historical notes, compiler-specific stuff, includes and ifdefs. imo, this is<br>
&nbsp;the implementation part, which should not be exposed to a user.<br>
<br>
so i'd suggest to completely remove the links to the c++ headers.</li>
so i'd suggest to completely remove the links to the c++ headers.<br>
&nbsp;</li>
<li>
<div class="im">
&gt; explaining the other builting types are not considered. Why only
big/little<br>
&gt; endianness has been taken in account?</div>
<p>I'll add FAQ and/or add more entries to the final docs.<br>
<br>
Only big/little endianness is taken into account because these are the<br>
only endian schemes that have any practical value. All the others are<br>
just historical curiosities.</li>
</ul>
<h3>Code</h3>
<p>Also change docs if applicable.</p>
<ul>
<li><span style="background-color: #FFCCFF">Beman: TODO</span><span style="background-color: #FFCCFF">:
</span><span style="background-color: #FFCCFF">Google</span><span style="background-color: #FFCCFF">
&quot;unaligned integer&quot;, look at various entries. For example, http://</span><span style="background-color: #FFCCFF">infocenter.arm.com</span><span style="background-color: #FFCCFF">/help/</span><span style="background-color: #FFCCFF">index.jsp?topic</span><span style="background-color: #FFCCFF">=/</span><span style="background-color: #FFCCFF">com.arm.doc.faqs</span><span style="background-color: #FFCCFF">/ka3544.html</span></li>
<li>Merge conversion2 into conversion.hpp</li>
<li>Use builtins where applicable (GCC, possibly others)</li>
<li>Endian integer types should use the conversion functions where applicable</li>
<li>Endian integer types should use the conversion functions where applicable.</li>
<li>Beman: Some platforms (compiler/processor taken together) don't require
alignment for the conversion functions if code is inlined, although speed may
suffer. (test to verify this assertion). On those platforms, conversion
functions (perhaps in-place) can be used to implement unaligned integers.<ul>
<li>Microsoft <a href="http://msdn.microsoft.com/en-us/library/ms253978.aspx">
UNALIGNED / __unaligned</a> keywords for pointers. Also
<a href="http://msdn.microsoft.com/en-us/library/ms253935.aspx">Packing
Structures</a>.</li>
<li>GCC
<a href="http://www.mailinglistarchive.com/gcc@gcc.gnu.org/msg21079.html">
http://www.mailinglistarchive.com/gcc@gcc.gnu.org/msg21079.html</a></li>
<li>Intel performs well on simple unaligned test. See
<a href="../test/unaligned_test.cpp">../test/unaligned_test.cpp</a></li>
</ul>
</li>
<li>Beman: Does the use of the unrolling templates get in the way of processor
specific optimization code?</li>
<li>Test use of endian integers with stream inserters and extractors.</li>
<li>Continue work on benchmarks and timings. Consider using use-case example
programs as benchmarks.</li>
<li>
<div class="im">
&gt; The reorder fuction should provide both reorder in place and returned.</div>
<p>Interesting, but providing two ways of doing something is often<br>
considered the not best design practice. And the tests I've run so far<br>
don't indicate any efficiency concern. Once all other aspects of the<br>
interface and implementation are settled, let's revisit that question.<br>
&nbsp;</li>
<li>&gt; The endianness scoped enum native should be replaced so it is defined<br>
&gt; depending on the endianess of the platform.<br>
&gt;<br>
&gt; &nbsp;BOOST_SCOPED_ENUM_START(<wbr />endianness) { big, little, native=(big or
little)<br>
&gt; }; BOOST_SCOPED_ENUM_END<br>
&gt;<br>
&gt; This will have the advantage to reduce of 1/3 the number of specializations.<br>
<br>
Does this work?<br>
&nbsp;</li>
<li dir="ltr">
<div class="im">
&gt; The library should provide in addition endian conversion functions that
have<br>
&gt; the endiannes as template parameters to make possible generic functions.</div>
<p dir="ltr">Compile time dispatch on an endianness enum was also requested in<br>
another review. That's fine with me, but I haven't had a chance to<br>
figure out the interface details.</li>
</ul>
<h3>Infrastructure</h3>
<ul>
@@ -131,13 +242,14 @@
&gt; might speed up the compilation time of the testsuite by something like
50ms ;)</div>
<p>Will do.</li>
<li>Make the bin() functionality available</li>
</ul>
<h3>Performance</h3>
<p>&nbsp;</p>
<h3>Acknowledge</h3>
<p>Gordon Woodhull, Hartmut Kaiser, Phil Endecott, tymofey, Giovanni Piero Deretta, Pyry Jahkola,
John Filo, Vitaly Budovski, Tomas Puverle, Vicente J. Botet Escriba, Tim
Blechmann, Daniel James, Mathias Gaunard</p>
Blechmann, Daniel James, Mathias Gaunard, Adder, Tim Moore</p>
<p>Paul Bristow docs help </p>