<html>
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<p>Of course 64 and 32 bit are the sizes, not the platform! That may
not be clear.<br>
</p>
<br>
<div class="moz-cite-prefix">On 5/24/2017 9:35 AM, Thaddy de Koning
wrote:<br>
</div>
<blockquote
cite="mid:4db5eca1-91be-564d-6803-444f199d01f7@thaddy.com"
type="cite">
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<p>Jonas, sorry for the late response:</p>
<p>The implementation is <u><b>not </b></u>undefined for
negative values,<u> unless you say that you define it as
undefined</u>.</p>
<p>Because you seem to have implemented it or most of it.<br>
</p>
<p>It renders a mathematical comparable distribution in the
negative to the positive values.</p>
<p>In both Turbo Pascal as in Delphi and because they use a
different algorithm and made an implementation error as well,
the negative values are indeed not defined. But that's because
of the algorithm and because of the implementation by Borland
(yes, it stems from Borland times).</p>
<p>The Mersenne Twister we use is also valid for negative values
and if you want I can send you the mathematical proof.</p>
<p>I already made the LCG in Delphi compatible mode available on
the wiki and that implementation differs in so far as that it
corrects the "undefined for negative values" for that algorithm
too. It is 100% compatible for the Delphi documented range, btw.</p>
<p>I am busy evaluating important Random implementions for
different languages, so an FPC library is available for data
that is generated in a different language and relies on a
particular PRNG.</p>
<p>Also note that the output of the current random is strictly
valid for 32 bit only.</p>
<p>In my code I already added a 64 bit version.<br>
</p>
<p>Regards,</p>
<p>Thaddy<br>
</p>
<p><br>
</p>
<p><br>
</p>
<br>
<div class="moz-cite-prefix">On 5/20/2017 2:57 PM, Jonas Maebe
wrote:<br>
</div>
<blockquote
cite="mid:79bb1be3-3814-9ce1-ff12-fb7f60829c92@freepascal.org"
type="cite">On 20/05/17 14:36, Martin Schreiber wrote: <br>
<blockquote type="cite">Is this intended? If not, which one is
correct? <br>
</blockquote>
<br>
random(x) is undefined for negative parameters. It should have
had an unsigned parameter, like in Turbo Pascal (where it is
word). Delphi defines it as always returning a positive value,
but I don't know what happens if you pass a negative parameter
there. <br>
<br>
<br>
Jonas <br>
_______________________________________________ <br>
fpc-devel maillist - <a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:fpc-devel@lists.freepascal.org">fpc-devel@lists.freepascal.org</a>
<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel">http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel</a>
<br>
</blockquote>
<br>
</blockquote>
<br>
</body>
</html>