> Date: Fri, 10 Apr 1998 15:48:43 -0700 (PDT)
> From: "Sean O'Keeffe" <sokeeffe@ucsd.edu>
> To: tveldhui@oonumerics.org
> 1. When compiling with egcs I get warnings about an initializer oredering
> problem on line 461 of array.h for the base initializer
> memoryBlockReference<T_type>.
Fixed, thanks.
> 2. I am writing some code that outputs and reads sequences of data into
> arbitrary rank Array objects. I don't want to specialize the routines
> based upon the data rank so I can't use TinyVector indices.
>
> I am currently casting away the const return value of dataFirst() member
> and writing directly from ptr[0] to ptr[size()-1]. This is pretty ugly
> and I think the correct approach is to define STL like bidirectional
> iterators that iterate over all element values using operator++ according
> to the order they are stored in memory. (Which may not be the best way
> for a human to view them but is very useful for simulations which need to
> checkpoint their state occasionally.)
>
> If you haven't already coded up something close to this I will give it a
> spin myself and submit it back to you. I just don't want to duplicate
> something that has already been done.
Writing an STL-style iterator for Array has been on my todo for
a long time. If you want to tackle it that would be a big help.
Also, your input/output code might be a useful start on an
array persistence mechanism.
Unfortunately a bidirectional iterator for Array<T,N> is a bit more
complicated than first appearances because of subarrays. In subarrays
you have to skip at the end of each row/column.
The easiest way I've found for doing this is using a stack-style
iterator. There is some code for doing stack
iteration in blitz/arrayeval.cc and blitz/arrayiter.h which
you could adapt if you wanted. See particularly evaluateWithStackTraversalN()
in blitz/arrayeval.cc. This routine only goes forward, but backward
might not be too hard. Even a forward iterator only would be
a big step forward.
That routine is a mess-- I will put in more comments.
There is some code in there to handle loop collapse (i.e. turn
an N-dimensional array traversal into a 1-dimensional array
traversal when possible). This could go in the ctor for your
iterator?
Anyway, let me know how I can help.
Cheers,
Todd
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