[jdom-interest] Performance tests

[Harwood Jim]

I tried the included sample code with a 229KB file composed almost
entirely of elements (sans attributes).  Interesting that JDOM cut the
read time roughly in half (a little over 600 milliseconds) but increased
memory usage by about 4%.  Are there any other benchmarking classes out
there?

philip.nelson at omniresources.com wrote:
> 
> > I used Xerces in the tests, but tried Crimson as well and
> > didn't see much difference.
> > The simple SAX parse time is less than 1/3 of the JDOM
> > document build time, and all
> > the tests except Electric XML use the same parser, so
> > changing the parser is not
> > going to dramatically change the results.
> 
> I am having trouble reproducing your results.  I used a variant of the
> Compare class that somebody sent in.  I added a little code to prime the
> builder by doing a sax parse of a simple in memory document for both DOM and
> JDOM (using SAXBuilder assuming that DOM would have to load the same
> classes).  I worked with a small, 8K document with lots of attributes and no
> namespaces in order to have a manageable trace file.  I did find a
> performance enhancement for Element.setAttribute that saved me about 8% but
> basically, the majority of time is spent outside of the JDOM classes.  We
> can save another 6-9% if we had a way to turn off the Verifier which is not
> needed when building but would be difficult to turn off.  With my
> enhancement, JDOM was faster than the default Xerces DOM build (deferred
> building) by a small margin.  I did not force Xerces to walk the tree.
> 
> I have included the patch for Element which should go in any case.
> removeAttribute is called *every time* setAttribute is called, whether it
> needs to be or not.  This means iterating through the entire list multiple
> times for every call.  My patch eliminates this for the most normal case of
> building a new document from xml source.
> 
> I have also included a screen shot of the JInsight visualization of the
> trace.  SAXBuilder.Build is a slice of the trace from the start of the
> build. The 100% time means the total time spent in that routine, not the
> total time for the full test.  SAXScanElement.gif shows that the majority of
> the time is not spent doing JDOM specific things.  It would appear that
> there is still room for optimization, but we're in the <20% range, at least
> for this document.  Most of the time is consumed by the parser itself.  I
> will test next with a document with namespaces and one with lots of element
> content.
> 
>     public Element setAttribute(Attribute attribute) {
>         if (attribute.getParent() != null) {
>             throw new IllegalAddException(this, attribute,
>                 "The attribute already has an existing parent \"" +
>                 attribute.getParent().getQualifiedName() + "\"");
>         }
> 
>                 //flag to help determine if we need to remove an old version
>         boolean preExisting = false;
> 
>         // Verify the attribute's namespace prefix doesn't collide with
>         // another attribute prefix or this element's prefix.
>         // This is unfortunately pretty heavyweight but we don't need to do
> it
>         // for attributes without a namespace, and a little testing shows no
>         // real difference in build times anyway.
>         String prefix = attribute.getNamespace().getPrefix();
> 
>         if (!prefix.equals("")) {
>           String uri = attribute.getNamespace().getURI();
>           if (prefix.equals(getNamespacePrefix()) &&
>                 !uri.equals(getNamespaceURI())) {
>               throw new IllegalAddException(this, attribute,
>                 "The attribute namespace prefix \"" + prefix +
>                 "\" collides with the element namespace prefix");
>           }
>           if (additionalNamespaces != null && additionalNamespaces.size() >
> 0) {
>               Iterator itr = additionalNamespaces.iterator();
>               while (itr.hasNext()) {
>                   Namespace ns = (Namespace) itr.next();
>                   if (prefix.equals(ns.getPrefix()) &&
>                         !uri.equals(ns.getURI())) {
>                       throw new IllegalAddException(this, attribute,
>                         "The attribute namespace prefix \"" + prefix +
>                         "\" collides with a namespace declared by the
> element");
>                   }
>               }
>           }
>           if (attributes != null && attributes.size() > 0) {
>               Iterator itr = attributes.iterator();
>               while (itr.hasNext()) {
>                       Attribute att = (Attribute)itr.next();
>                   Namespace ns = att.getNamespace();
>                   //keep track if we have and existing attribute
>                   if (attribute.getName().equals(att.getName()) &&
>                           ns.getURI().equals(att.getNamespaceURI()))
>                                 preExisting = true;
> 
>                   if (prefix.equals(ns.getPrefix()) &&
>                         !uri.equals(ns.getURI())) {
>                       throw new IllegalAddException(this, attribute,
>                           "The attribute namespace prefix \"" + prefix +
>                           "\" collides with another attribute namespace on "
> +
>                           "the element");
>                   }
>               }
>           }
>         }
> 
>         if (attributes == null) {
>             attributes = new LinkedList();
>         }
>         else if (preExisting) {
>             // Remove any pre-existing attribute
>             removeAttribute(attribute.getName(), attribute.getNamespace());
>         }
> 
>         attributes.add(attribute);
>         attribute.setParent(this);
>         return this;
>     }
> 
>   ------------------------------------------------------------------------
>                          Name: SAXScanElement.gif
>    SAXScanElement.gif    Type: GIF Image (image/gif)
>                      Encoding: base64
> 
>                           Name: SAXBuilderBuild.gif
>    SAXBuilderBuild.gif    Type: GIF Image (image/gif)
>                       Encoding: base64
> 
>                           Name: Compare.java
>    Compare.java           Type: Java File (Forte for Java) (application/x-unknown-content-type-javafile)
>                Download Status: Not downloaded with message
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