You seem to be expecting that two pseudo-random sequences starting with
different seeds will have no discernable relationship to each other. That
might be a property of some randomizers, but it is not necessarily a
property of every randomizer, and it appears not to be true of this one. The
best you can expect is that within a random sequence, each number is
unrelated to the previous one. I would suggest that rather than adding 11 to
the seed for your first sequence to get the seed for your second sequence,
you use the first ("primary") seed to get a random set of numbers which you
then use as "secondary" seeds for the subsequent sequences.
Regards,
Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay
-----Original Message-----
From: jesper(_dot_)tverskov(_at_)gmail(_dot_)com
[mailto:jesper(_dot_)tverskov(_at_)gmail(_dot_)com] On Behalf Of Jesper
Tverskov
Sent: 06 October 2009 10:35
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: [xsl] Seed problem in FXSL randomizeList
I have tested the FXSL randomizeList template for a list of
type items/item. For each item I want the positions of the
other item elements returned in random order, and I need to
make use of the first four items in each random order.
The items/item list I have used so far has 140 item elements.
I have managed to solve the above using recursion, Saxon and
the command line. Processing time is a little less than 10s.
The first seed is made like this
xs:integer(format-time(current-time(),
'[s][f]')). For the next seed I add 11, etc. It is a mystery
to me, that if I increase the values of "11" to just "12" the
transformation seems to go looping. Millions of lines are
generated and I have to stop the process. (I have tested this
strange behavior many times).
Also the random order of the positions returned, are not that random.
The first third of my lists start with the same position
number, the next third of the list adds just one to this
number, and the last third of the list adds two. The rest of
the positions look ok, at least I have not yet recognized a pattern.
_Here is my question_.
Is there anything I can do to get "random" lists returned,
that are more "random" for the first position? And how can I
change the XSLT stylesheet so it will also work for lists of
items of at least a couple of thousands without the need for
experimenting to find a number to add to the first seed that
will not break the transformation?
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
xmlns:f="http://fxsl.sf.net/";
xmlns:xs="http://www.w3.org/2001/XMLSchema";
exclude-result-prefixes="f xs">
<xsl:import
href="../../../../XSLT/fxsl-xslt2/fxsl-xslt2/f/randomList.xsl"/>
<!-- Can be applied on any source xml document (ignored) -->
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:template match="/">
<items>
<xsl:call-template name="item"/>
</items>
</xsl:template>
<xsl:template name="item">
<xsl:param name="pSeed" as="xs:integer"
select="xs:integer(format-time(current-time(), '[s][f]'))"/>
<xsl:param name="num" select="1" as="xs:integer"/>
<item>
<name>
<xsl:value-of select="/items/item[$num]/name"/>
</name>
<xsl:variable name="x">
<xsl:call-template name="randomizeList">
<xsl:with-param name="pList" select="(1 to
count(/items/item))[. != $num]"/>
<xsl:with-param name="pSeed" select="$pSeed" as="xs:integer"/>
</xsl:call-template>
</xsl:variable>
<positions>
<xsl:sequence select="$x/el[position() < 5]"/>
</positions>
</item>
<xsl:if test="$num < count(/items/item)">
<xsl:call-template name="item">
<xsl:with-param name="pSeed" select="$pSeed + 11"
as="xs:integer"/>
<xsl:with-param name="num" select="$num + 1" as="xs:integer"/>
</xsl:call-template>
</xsl:if>
</xsl:template>
</xsl:stylesheet>
Cheers,
Jesper
http://www.xmlplease.com
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