[chrjohn]

Claude's take on performance optimization.

Java changes (MessageCodeGenerator.java)

1. The dictionary is converted to Saxon's own tree format once per version. Before, every generated file (thousands of them) was transformed from a DOMSource, so Saxon redid the DOM conversion each time. The DOM parse itself, with its security settings, is unchanged; the converted tree is cached next to it. This was the biggest single gain.
2. Each stylesheet is compiled once. Before, a new TransformerFactory was created and the XSL recompiled for every phase of every version. Now one factory and a cache of compiled stylesheets are used, keyed by the XSL's path, so custom transformDirectory stylesheets still take priority.
3. Settings that are the same for every file are set once per loop, so only fieldName/itemName changes per file. The utcTimestampPrecision check also moved out of the per-field loop.

Stylesheet changes
4. Fields.xsl: to generate one field, the fix template walked every element of the dictionary, including all messages and components. It now goes straight to fields/field[@name=$fieldName], which removes a cost that grew with the square of the dictionary size.
5. Message.xsl, MessageSubclass.xsl, MessageFactory.xsl: field and component lookups by name, like /fix/fields/field[@name=$name], scanned the whole list every time. They now use xsl:key indexes. The //component[@name=$myname] lookups use a key on all component elements, so they return exactly the same nodes as before.

Custom stylesheets keep working because they receive the same document; only its internal form changed.

	FIX50SP2	FIX44	FIX42	Total
Before	36.3s	8.0s	0.8s	45.1s
Java changes only	7.4s	1.6s	0.2s	9.2s
+ stylesheet changes	2.1s	0.3s	0.06s	2.4s