<div dir="ltr"><div>You can prevent this particular optimization-to-constant by declaring sum '<a href="https://en.wikipedia.org/wiki/Volatile_(computer_programming)">volatile</a>' as below:</div><div><br></div><div>#include <stdio.h><br><br>int main(void) {<br> volatile long sum = 0;<br><br> for (long i = 1; i <= 100000000L; ++i) {<br> sum += i;<br> }<br> printf("%ld\n",sum);<br> return 0;<br>}</div><div><br></div><div>I don't know if this provides the comparison you're looking for, but it does force the compiler to emit assembly to do the summation.<br></div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div>--<br>vale cofer-shabica<br>401.267.8253</div></div></div></div>
<br><div class="gmail_quote">On Tue, Feb 27, 2018 at 12:26 PM, Ryan Reich <span dir="ltr"><<a href="mailto:ryan.reich@gmail.com" target="_blank">ryan.reich@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto">In other words, it's not competition with the language C but with its popular compiler. Choose an example that doesn't simplify and you'll get a fairer contest.</div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Feb 27, 2018 07:52, "Brandon Allbery" <<a href="mailto:allbery.b@gmail.com" target="_blank">allbery.b@gmail.com</a>> wrote:<br type="attribution"></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Tue, Feb 27, 2018 at 10:06 AM, Dušan Kolář <span dir="ltr"><<a href="mailto:kolar@fit.vut.cz" target="_blank">kolar@fit.vut.cz</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>
<div style="font-family:'Hack';font-size:9pt;font-weight:400;font-style:normal">
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"><span style="font-size:9pt">Unfortunately, in this case the C is much more faster (it prints the result immediately), at least on my machine. Is it due to a fact that C compiler does a brutal optimization leading to compile-time evaluation, while ghc is not able to do that?</span><br></p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"></p></div></blockquote><div><br></div><div>ghc is less prone to invoke that kind of optimization, but sometimes can do so. And yes, gcc is decidedly "brutal" with -O2: inspect the generated assembler and you'll find that it just prints a constant.</div></div><div><br></div>-- <br><div class="m_8687034308571433962m_5952026264623483734gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div>brandon s allbery kf8nh sine nomine associates</div><div><a href="mailto:allbery.b@gmail.com" target="_blank">allbery.b@gmail.com</a> <a href="mailto:ballbery@sinenomine.net" target="_blank">ballbery@sinenomine.net</a></div><div>unix, openafs, kerberos, infrastructure, xmonad <a href="http://sinenomine.net" target="_blank">http://sinenomine.net</a></div></div></div>
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