Re: [vsipl++] [patch] Add byte-swapping support to save/load_view.hpp

[Jules Bergmann <jules@xxxxxxxxxxxxxxxx>]

Don McCoy wrote:
> There were two problems with the previous version of this patch.  First,
> the save_view function was reversing the bytes in the view in-place. 
> This has been fixed by forcing it to copy the view so as to avoid this
> problem.  Second, complex values were being handled incorrectly, i.e.
> for complex floats, the entire 8-byte quantity was being swapped leading
> to the reversal of the imaginary and real components.  The correct
> operation is to perform two, four-bytes swaps.
>
> Regression tests for the above were added.
Don,

This look good, please check it in.

There are a couple of things we could do to further optimize
save_view, on a rainy day:

 - in save_view when it is necessary to swap bytes, instead of copying
   and then swapping bytes as two steps, it would be more efficient
   to perform that as a single step (copy & swap in one step).

 - also in save_view, instead of copying the entire view (which requires
   a potentially large temporary allocation), you could copy/swap the
   view in chunks.  The chunk size might be chosen (a) large enough for
   fwrite to be efficient and (b) small enough to live on the stack.

			-- Jules

--
Jules Bergmann
CodeSourcery
jules@xxxxxxxxxxxxxxxx
(650) 331-3385 x705