> Bruce Partridge wrote:
> > This is the code I timed:
> >  for (i=0; i<16; i++)
> >     {
> >        temp_array1[i] = array1[i];
> >        temp_array2[i] = array2[i];
> >     }
> >
> > All of the arrays are 32 bit float.
>
> Argh!  This is exactly the kind of reason you need to know what
> you're doing
> at the machine laguage level, whether using assembler or a compiler.
> Apparently this is on an 18 family PIC.  You could unroll the whole loop
> into 128 MOVFF instructions if program space is not a problem.  The next
> fastest method would be to make good use of the autoincrement FSRs.  This
> may be difficult for the C compiler to figure out.  This is very likely
> prevented altogether by putting both copy operations in the same loop.
> Again *THINK* about what has to go on.  If you did one array, then the
> other, you could blast thru each array without having to reload FSRs.
> Switching arrays every 4 bytes is silly.  I'd be real impressed if the
> compiler could rewrite this as two separate array copies.

Thanks.  Thats great information.  I have used other assemblers, but I am
pretty new to PIC assembler.

Although it appears I am going to have the code space and cycles to get this
running (just), I will probably be able to pick up a lot by going over the
assembler in detail.

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