xsl-list
[Top] [All Lists]

Re: [xsl] To determine the distinct elements in a sequence of 46,656 elements takes 5 hours of XSLT processing

2012-08-19 18:12:13
Try the following:

count(distinct-values(map/f:signature(.))

where f:signature is

<xsl:function name="f:signature">
  <xsl:param name="map" as="element(map)">
  <xsl:variable name="sorted-map" as="element(singletonMap)*">
    <xsl:perform-sort select="$map/*">
        <xsl:sort select="@from"/>
        <xsl:sort select="@to"/>
    </xsl:perform-sort>
  </xsl:variable>
<xsl:sequence select="string-join($sorted-map/concat(@from, '~', @to), '|')"/>
</xsl:function>

Michael Kay
Saxonica


On 19/08/2012 23:43, Costello, Roger L. wrote:
Hi Folks,

I have a sequence of 46,656 elements that I call "maps."

Here is one map:

     <map id="Planes-Enroute-to-Airports">
         <singletonMap from="F16" to="DFW"/>
         <singletonMap from="B707" to="ORD"/>
         <singletonMap from="F35" to="MIA"/>
         <singletonMap from="S340" to="LAX"/>
         <singletonMap from="A320" to="SFO"/>
         <singletonMap from="MD90" to="DEN"/>
     </map>

I wrote a function to return all of the distinct maps.

Unfortunately it takes about 5 hours of XSLT processing.

Perhaps my XSLT program is inefficient.

I am hoping that you can show me a more efficient program or identify where my 
program is inefficient.

I am using XSLT 2.0.

Here is my function to return all distinct maps:
<xsl:function name="ct:distinct" as="element(map)*">
         <xsl:param name="maps" />
<xsl:variable name="new-maps">
             <maps>
                 <xsl:sequence select="$maps" />
             </maps>
         </xsl:variable>
         <xsl:for-each select="$new-maps/maps/map">
                 <xsl:if test="not(ct:contained-within(., 
./following-sibling::map))"><xsl:sequence select="." /></xsl:if>
         </xsl:for-each>
</xsl:function>

The following function determines if a map is contained within a sequence of 
maps; it uses a binary divide-and-conquer approach:
<xsl:function name="ct:contained-within" as="xs:boolean">
         <xsl:param name="map" as="element(map)"/>
         <xsl:param name="maps" as="element(map)*"/>
<xsl:variable name="cnt" select="count($maps)" /> <xsl:choose>
             <xsl:when test="$cnt eq 0"><xsl:value-of select="false()" 
/></xsl:when>
             <xsl:when test="ct:equal($map, $maps[1])"><xsl:value-of select="true()" 
/></xsl:when>
             <xsl:when test="$cnt eq 1"><xsl:value-of select="false()" 
/></xsl:when>
             <xsl:otherwise>
                 <xsl:variable name="half" select="$cnt idiv 2" />
                 <xsl:choose>
                     <xsl:when test="ct:contained-within($map, $maps[position() = (2 to 
$half)])"><xsl:value-of select="true()" /></xsl:when>
                     <xsl:otherwise><xsl:value-of select="ct:contained-within($map, 
$maps[position() = (($half + 1) to last())])" /></xsl:otherwise>
                 </xsl:choose>
</xsl:otherwise>
         </xsl:choose>
</xsl:function>

Two maps are equal iff for each singletonMap in map1 there is a singletonMap in 
map2 with the same value for @to and @from:
<xsl:function name="ct:equal" as="xs:boolean">
         <xsl:param name="map1" as="element(map)"/>
         <xsl:param name="map2" as="element(map)"/>
<xsl:choose>
             <xsl:when test="count($map1/*) ne count($map2/*)"><xsl:value-of 
select="false()" /></xsl:when>
             <xsl:otherwise>
                 <xsl:variable name="result">
                     <xsl:for-each select="$map1/singletonMap">
                         <xsl:variable name="here" select="." />
                         <xsl:if test="$map2/singletonMap[@from eq $here/@from and @to ne 
$here/@to]">false</xsl:if>
                     </xsl:for-each>
                 </xsl:variable>
<xsl:choose>
                     <xsl:when test="contains($result, 'false')"><xsl:value-of 
select="false()" /></xsl:when>
                     <xsl:otherwise><xsl:value-of select="true()" 
/></xsl:otherwise>
                 </xsl:choose>
             </xsl:otherwise>
         </xsl:choose>
</xsl:function>

/Roger

--~------------------------------------------------------------------
XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list
To unsubscribe, go to: http://lists.mulberrytech.com/xsl-list/
or e-mail: <mailto:xsl-list-unsubscribe(_at_)lists(_dot_)mulberrytech(_dot_)com>
--~--




--~------------------------------------------------------------------
XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list
To unsubscribe, go to: http://lists.mulberrytech.com/xsl-list/
or e-mail: <mailto:xsl-list-unsubscribe(_at_)lists(_dot_)mulberrytech(_dot_)com>
--~--