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On 2012-06-01 15:09, Gustav Simonsson wrote:
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On 2012-06-01 12:07, Björn-Egil Dahlberg wrote:
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<div>1 jun 2012 kl. 10:46 skrev "José Valim" <<a
moz-do-not-send="true" href="mailto:jose.valim@gmail.com">jose.valim@gmail.com</a>>:<br>
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<div class="im">The '++' operator does not verify that
the second argument is a list.</div>
Therefore, the compiler will rewrite the first
expression to simply:<br>
<br>
[$F,$o,$o|Bar]<br>
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<div>Yes, thanks. <span style="">For some weird reason I
thought Erlang restricted the right side to be a list
in such cases.</span></div>
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<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex"> Have
you made sure that you run each test in a newly spawned
process? </blockquote>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex"> Do
you run the test for long enough time?<br>
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<div>Running in a newly spawned process did the trick, the
results are now consistent.</div>
<div>I was already running it 1000 times, here is the code
(without using spawn):</div>
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<div><a moz-do-not-send="true"
href="https://www.refheap.com/paste/2954">https://www.refheap.com/paste/2954</a></div>
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<div>I assume having a "clean" heap (reducing the chance
of garbage collection) is the reason why it is a good
idea to run benchmarks in a newly spawned process?</div>
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If you want to vary one parameter in a test, make sure all other
parameters stays the same otherwise you have no idea what you
are measuring!
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<div>Code loading, heaps, position of mars .. Everything has to
be taken into account.<br>
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The effect of Mars magnetic field on that of Earth, even if
Earth's aphelion and the perihelion of Mars were to <span
class="hw">coincide and the interplanetary distance were to be
at its theoretical minimum, is </span>negligible compared to
the normal variations in Earth's magnetic field. <br>
<br>
Therefore it's very unlikely that the relative position of Mars
would affect the probability of a memory bitflip occurring due to
cosmic radiation and thus affecting the benchmark.<br>
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My point, in case you missed it, is that you can't disregard
something out of hand. You have to be sure. In physics you might be
familiar to similar topics from dimensional analysis, i.e. how to
come up with a model and how to disregard useless parameters.<br>
<br>
All I'm saying is that you should be sure of what you are measuring.
=)<br>
<br>
<blockquote cite="mid:4FC8BEF5.3000006@erlang.org" type="cite"> <br>
Regards,<br>
Gustav Simonsson<br>
Erlang/OTP team<br>
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<div>Thanks Björn!</div>
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