On Dec 21, 2012, at 2:32 PM, Siegmar Gross wrote: > Today I found something about the memory layout of 2D matrices in > Java (I'm not sure if the information is valid). Java has one 1D array > with pointers to every 1D row. All elements of a row are stored in > contiguous memory. Different rows can be stored in "arbitrary" places > so that a 2D matrix is normally not stored in a contiguous memory area.
This makes it sound just like C -- in that if you want a contiguous chunk of memory for an N dimensional array, you need to write a wrapper method that allocates a contiguous chunk of memory and then sets all the pointers properly so that successive rows/columns/etc. point to the Right places in memory. This wrapper will likely need to be written in C. > In fact it would be better in that case if the extent of a new column > type is equal to the extent of the base type of the array. Yes, via a "resized" type. The basic MPI bindings should do pretty much exactly what the MPI C bindings should do. > It would also > be necessary that a new column type is something like an array itself > pointing for example to the first element of each row (perhaps it is > even possible to use the Java pointer array of the 2D matrix). To make > things worse, Java allows non-rectangular matrices (but they could be > prohibited for MPI). Perhaps this is no news to you, but I wanted to > mention it in case you also didn't know (as I said I'm not sure if the > information about 2D Java matrices is true). Nope, I don't know very much about Java at all. :-) -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
