On Thu, Nov 15, 2012 at 10:04 AM, Phil Steitz <phil.ste...@gmail.com> wrote:
> Do you know how to do that with a primitive array? Can you provide > some sample code? > You don't. See my next paragraph. See the assign method in this class: https://github.com/apache/mahout/blob/trunk/math/src/main/java/org/apache/mahout/math/VectorView.java > > Thanks for your help on this. > > Phil > > > > The Colt/Mahout approach is to define a view object which opaquely > > remembers a reference to the original, an offset and a length. Functions > > and other arguments can be passed to this view object which operates on a > > subset of the original contents by calling the function. Performance is > > actually quite good. The JIT seems to in-line the view object access to > > the underlying object and also in-lines evaluation of the function so > that > > the actual code that is executed is pretty much what you would write in > C, > > but you don't have to worry as much since the pattern of access is more > > controlled. > > > > For completeness, this is essentially what java.nio does with the *Buffer > > classes as well. You can wrap an array and then you can ask for slices > out > > of that array while retaining the reference semantics. > > >
