On Mar 9, 2010, at 1:28 AM, Per Vognsen wrote: > Which is preferable depends on the nature of the changes that your > matrices will undergo. For dense linear algebra, it's common for most > of a matrix to change with every operation. Hence you won't reap any > benefits from the persistence of Clojure's maps. > > The problem with your first implementation isn't the use of flat > arrays but the fundamental inefficiency of a low-level > get-entry/set-entry interface. Even for a mutable matrix data > structure, I would consider such a thing. >
Sure. BTW, I am not trying to build a matrix library. What I was looking to do was understand the various ways of binding heterogeneous state together in clojure, and used a simple matrix function as an example. So far have learned that maps are pretty fast, though slower than the equivalent object member access. > Many sequence operations and virtually all linear algebra operations > produce matrices with a shape and size that is predictable ahead of > time. Mapping a function over a matrix yields a matrix of the same > size (an example is scalar multiplication). Mapping a function over > two matrices of the same size yields a matrix of the same size (an > example is matrix addition). Transposing a matrix of size m x n yields > a matrix of size n x m. Multiplying a matrix of size m x p with a > matrix of size p x n yields a matrix of size m x n. Indeed. For matrix work I use the ejml library. My example was just for learning purposes. Thanks for all of the feedback > > These are the kind of primitive operations you should build your > interface on. With this, you can use float-arrays preallocated to just > the right size, fill in the entries by whatever means (e.g. calls to > user-provided functions in the case of mapping), and return that. > Everything is purely functional from the exterior. I agree that for most matrix work it is appealing to use in a pure-functional form externally. > > -Per -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
