Blitz limitation with the debugging mode

Created by: laurentes

Blitz has a current limitation when combining reduction and complex expressions, AND enabling the debugging mode using the -DBZ_DEBUG flag. This problem is described in this blitz ticket.

In particular, this means that such a piece code will throw an assert when the DBZ_DEBUG flag is set, but will work fine otherwise:

  blitz::firstIndex  bi; 
  blitz::secondIndex bj; 
  blitz::thirdIndex  bk; 
  blitz::Array A(2,2,2);
  A = 2.; 
  blitz::Array B(2,2);
  B = 7.; 
  blitz::sum(A(bi,bj,bk)*B(bi,bj),bk); // throws an assert 
  //   linux-x86_64/include/blitz/array/expr.h:492 Two array operands have different orders: for rank 0, the orders are 2 and 1
  //   linux-x86_64/include/blitz/array/expr.h:493: static int blitz::bounds::compute_ordering(int, int, int): Assertion `0' failed.

More precisely, this happens when the expression inside the reduction is built on arrays of different dimensions. The current workaround to make everything work with the DBZ_DEBUG flag enabled is to declare an intermediate array:

   blitz::Array C(A(bi,bj,bk)*B(bi,bj));
   blitz::sum(C,bk); // throw an assert

Please be aware that this might generate some overhead.