On Thu, 2006-11-23 at 17:20 +0100, Johan Dahlin wrote: > You seem to be very worried about performance. Only for low-level code, where C would be used for efficiency. Ideally, calling C methods from C code should be as fast as invoking a function via a function pointer (possibly achieved by caching the method lookup). Calling Python from C or C from Python can involve hashtable lookups, performance is obviously not a priority there. > I advise you to try it out and see if it meets your requirements. > > If it doesn't, rewrite the whole thing in C. Your advice is sound and it works well for most projects. For some larger projects a bit more planning is needed because by the time the project reaches a prototype stage, it might be too late to rewrite it in C. In the case of the project I'm working on, the prior code base was written in Scheme, using an interpreter I will call "Morass" to protect the innocent. An object system was designed on top of Morass's CLOS implementation, and Morass's GTk bindings were bound to these custom objects to form the GUI layer. Authors paid little attention to performance during design and implementation, planning instead to make it work first and then rewrite the components that proved too slow in C, on a case-by-case basis. By the time a working prototype was reached, a large chunk of code was already written. Unfortunately, the prototype turned out to be very slow: it loaded for a long time, and the GUI that used it proved too sluggish to use. After many attempts to profile and optimize it, it was still too slow. And this was only in a small program that was written to demonstrate the system, which was supposed to also be usable in a wide range of applications. At this point, it was definitely too late for a full rewrite in C. The system was written in a purely interpreted dynamic language augmented with a highly flexible dynamic OO system customized with MOP. It created a multiple of objects which were in reality heavyweight due to the dynamic nature of the language. It was far from obvious which parts to "rewrite in C" to get a measure of speed. Rewrite Morass's reader to get better loading performance? Implement a compiler for Morass to get better run-time performance? Rewrite implementation of some CLOS objects in C? Given the nature of the underlying technology and the use of MOP, any one of those projects would be a major undertaking, and it is questionnable whether any one alone would significantly boost performance. The moral of the story is not premature optimization, nor is it my intention to imply that Python is as slow as Morass (it's in fact significantly faster, although not by an order of magnitude). The point is that performance has to be at least considered when choosing the underlying technology and design, because the underlying technology is hard to change later without a major rewrite. _______________________________________________ gtk-list mailing list gtk-list@xxxxxxxxx http://mail.gnome.org/mailman/listinfo/gtk-list
