Hi,<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div lang="EN-GB" link="blue" vlink="purple"><div><div style="border:none;border-left:solid blue 1.5pt;padding:0mm 0mm 0mm 4.0pt">
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<p class="MsoNormal"><span style="font-size:10.0pt">The
initial intent was log2(0) = -1, you can check if your compiler isn&#39;t GCC
that count_leading_zeros(T(0)) is always sizeof(T) * 8 (all bits are
leading zeros). </span></p>

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<p class="MsoNormal"><span style="font-size:10.0pt">But
one of the intents of this implementation is performance so, using compiler
optimized functions is desired.</span></p>

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<p class="MsoNormal"><span style="font-size:10.0pt"> </span></p>

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<p class="MsoNormal"><span style="font-size:10.0pt">So
the function to be analyzed in this case is count_leading_zeros.</span></p>

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<p class="MsoNormal"><span style="font-size:10.0pt"> </span></p>

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<p class="MsoNormal"><span style="font-size:10.0pt;color:#1F497D">I can see the ‘need for speed’, but that doesn’t
change the argument for using policies to allow users to control at compile
time how exceptional situations are handled.  Policies should have no
effect on run time, apart from any checks implied by the chosen policy.  </span></p><div class="im">

<p class="MsoNormal"><span style="font-size:10.0pt;color:#1F497D"> </span></p>

<p class="MsoNormal"><span style="font-size:10.0pt;color:#1F497D">Paul</span></p></div></div></div></div></div></div></blockquote><div><br></div><div>Paul:</div><div> </div></div>What if I make 2 versions of ilog2:<div><ul>
<li>unchecked_ilog2(T value) - don&#39;t checks the input value</li><li>ilog2(T value) - returns -1 if value == 0 else returns unchecked_ilog2(value)</li></ul><div>Following the line of:</div><div><a href="http://www.boost.org/doc/libs/1_43_0/libs/math/doc/sf_and_dist/html/math_toolkit/special/factorials/sf_factorial.html">http://www.boost.org/doc/libs/1_43_0/libs/math/doc/sf_and_dist/html/math_toolkit/special/factorials/sf_factorial.html</a></div>
<div><br></div><div>Steven:</div><div><br></div><div>I will maintain the name ilog2 for now. </div><div><br></div><div><br></div><div>Best,</div><div><div><br>-- <br>Murilo Adriano Vasconcelos<br><a href="http://murilo.wordpress.com">http://murilo.wordpress.com</a><br>

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