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Firstly, the variable $net is a sequence of elements that are essentially (x,
y) pairs, and my instinct is that using sequence of maps would cut a lot of
node-creation cost (and a bit of number-to-string and string-to-number
conversion). In fact, since you are computing the (x, y) pairs only in order
to then compute the sum of the x's and the sum of the y's, it seems
unneccessary to capture these values in a list in the first place; why not
compute the two totals as you go by using xsl:iterate in place of xsl:for-each
at line 325?

Line 313 is

<xsl:param name="force-nodes" select="key('nodes', ('circle', 'rect'))"

where the key is

<xsl:key name="nodes" match="svg:g[svg:circle] | svg:g[svg:rect]"
use="concat(svg:circle/local-name(), svg:rect/local-name())"/>

This is going to create a key with a very small number of entries, each
indexing a large number of nodes, and that doesn't feel like an efficient
thing to do.

At lines 339 and 343, should the following-sibling calls be limited (using
[1]) to the immediatelty following sibling?

At line 343, should the generate-id() comparison be replaced by "is"? (The XJ
compiler does this optimisation for you, XX doesn't).

Finally, line 360-366 is a classic case of a subtree copy that's making a very
small change to an existing tree; I've written several papers that attempt to
address the problem that this is very inefficient because it involves copying
the whole tree.

You might consider, instead of making incremental modifications to the
attributes of the svg:g elements, maintaining for each of these elements a map
containing the original svg:elements and the latest computed values of the
attributes that are being modified. Changing a single property in a map is
much more efficient that changing a single attribute of an element.

This would also address another issue: on each iteration where a node is
repositioned, you're generating an SVG @transform attribute to reflect the new
position, and then on the next iteration, you are parsing this attribute to
compute the current position. Much better, surely, to maintain the actual

Michael Kay

> On 14 Oct 2020, at 22:00, Martynas JuseviD
ius martynas@xxxxxxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hi,
> could anyone suggest any optimizations to this stylesheet that
> transforms a graph encoded as RDF/XML to an SVG directed graph layout:
> Output example: https://twitter.com/namedgraph/status/1316476355874304001
> The problem is that it's quite slow: <100 nodes and 5 steps take a few
> minutes running on Saxon-JS 2 in Firefox or Chrome.
> It's based on a paper on force directed layout in XSLT: "GraphML
> Transformation":
> The algorithm:
> 1. position resource nodes (optionally also literals) randomly.
> (TO-DO: position on an ellipse?)
> 2. move nodes in a loop using the force-directed algorithm
> 3. draw lines between the nodes, calculating the correct intersection
> with the node border
> Note: only "flat" RDF/XML (properties grouped into descriptions; no
> nesting) is supported. It's called RDFXML_PLAIN in Jena.
> If anyone would like a sample file, I can easily provide :)
> Martynas
> atomgraph.com

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