Deitte.com

I just did some stopwatch performance tests of Flash Builder 4 against Flex Builder 3, using the same files that I did for the faster Flex 3 SDK tests. Here are the results:

Build All, in seconds, after changing two UI classes
Flex 3: 42.5
Flex 3 fast: 36
Flex 4: 38
Flex 4 with libraries: 26.5

Build All, in seconds, after changing a ModelLocator
Flex 3: 47
Flex 3 fast: 36.5
Flex 4: 34
Flex 4 with libraries: 26

The projects with libraries were very impressive. For these admittedly simple performance tests, I'm seeing the best Flex 4 project as 70% faster than the regular Flex 3 project.

The "Flex 3 fast" and "Flex 4" results are so similar because some of the improvements are already in Faster Flex 3 SDK. This was unexpected to me, so I ran a few more tests. Sure enough, some more complicated compilations showed more of an improvement for Flex 4.

The "Flex 4 with libraries" test took advantage of the library sharing and other multiple project work that has gone into Flash Builder 4. The project that I was building was divided into three library projects and one main project. The library projects only have acyclical dependencies, which likely made the compilation easier.

More details on the test: the Flex 3 tests were done in Flex Builder 3 using 3.2 or the modified version of 3.2 from the faster Flex 3 SDK page. The Flex 4 tests were done in the beta of Flash Builder 4. The project was simply converted for Flash Builder 4, and only two simple changes to the code were needed to build the project. I only reran two of the three tests from the Faster Flex SDK page for no good reason. I ran each build a few times and averaged out the results.