these points to some extent and provides some other nice properties such as allowing transposition of arbitrary indices with no need to reorder the underlying storage (that is mat.transpose(0,1) causes all subsequent calls to mat(i,j) to provide the transposed element without moving the elements themselves). I have
I'd be interested in seeing how this was done, especially in comparison with Timothy Budd's methods in _An Apl Compiler_. I had an implementation of this; however, it was only for dense matrices since that's all Budd had in his book.
What I do is maintain a signature of permutations (essentially the index order : for example, in a 3D C array the signature would be (0,1,2) while a FORTRAN order array would be (2,1,0). An accessor class is responsible for converting between the multidimensional index and a one dimensional offset corresponding to a dense matrix; the allocator then uses this offset to get the element out of storage - if the matrix is dense, the allocator just passes the already computed offset along, while if it is sparse, a map is used to look for the existence of the specified element. ------------------------------------------------------------------------ --------------------------- Matthias Schabel, Ph.D. Utah Center for Advanced Imaging Research 729 Arapeen Drive Salt Lake City, UT 84108 801-587-9413 (work) 801-585-3592 (fax) 801-706-5760 (cell) 801-484-0811 (home) mschabel at ucair med utah edu