ThreadWeaver News: Collections and Sequences

For those who are not familiar with it: ThreadWeaver is like a multi-threaded make tool for application developers. It provides means to chop operations into jobs and declare the way they depend on each other. When started, the jobs will be executed by a pool of threads, which will automagically try to find the most efficient order of execution. With the lately released version 0.5, it now has job collections, job sequences, and qtestlib based unit tests.

When ThreadWeaver was introduced at last year's KDE conference, a number of concepts have been suggested for addition to it. One of the concepts where collections of jobs, another one sequences. Both are now finished and have been moved from the experimental to the main code base.

As an interesting implementation detail, JobCollections are Jobs themselves. They can be created and queued, just like any other Job. This allowed for the removal of all other queueing methods, making the WeaverInterface class even more simple.

JobSequences in turn are implemented as JobCollections, but will execute all jobs they contain in the order they where added. This raises an interesting question - what if I add a number of sequences to a sequence? Intuitively, it would be expected that the sub-sequences will be executed in the order they in turn where added. This is exactly what happens. More general, ThreadWeaver's job collection classes allow recursive queueing of subjobs. A number of unit tests have been added to showcase this.

The next features to come will be pooled resources (aka Job categories). Think of local IO intensive Jobs - maybe you want a maximum of 2 of those running at the same time. There will be special job classes for this purpose.

Currently I am thinking about the best way to add the idea of progress to the Job class. Of course we can use a special job class, but inheritance does not seem to be the best way to go. What if what the user wants is a sequence that has a progress property? On the other hand, I hesitate to simply add a progress property to the Job base class. Let us see if the future brings a nice idea of composition ...

ThreadWeaver is in KDE SVN (kdenonbeta/threadweaver). Release 0.5 has been tagged in tags/others/threadweaver/0.5.