Re: Data types (was: Re: Access the neighbors of an element)

[Paul Kienzle]

On Feb 14, 2005, at 8:41 PM, John W. Eaton wrote:

> On 14-Feb-2005, Paul Kienzle <address@hidden> wrote:
>
> | This message didn't get back to me.  Was it perhaps a problem with 
> the
> | attachment?
>
> I saw it and it made it to the archives:
>
>   http://www.octave.org/mailing-lists/help-octave/2005/384

I don't understand why I didn't see it on my box.

I did want it for general distribution so that those who may be
motivated to have faster integer ops can do the necessary work.

> Sorry I haven't had time to comment on it yet.  I think it is a nice
> idea, but since you show that the speedups vary, we will need some
> configure or (better) runtime tests to decide exactly what code to
> use.

The speedup on Intel is so big:

  $ gcc -O2 uint.c -DLONG -DDOUBLESAT -DADD; time ./a.out 5
  real    0m20.633s
  $ gcc -O2 uint.c -DLONG -DSAT -DADD; time ./a.out 5
  real    0m1.550s
  $ gcc -O2 uint.c -DLONG -DNOSAT -DADD; time ./a.out 5
  real    0m0.973s

  $ gcc -O2 uint.c -DLONG -DDOUBLESAT -DMULT; time ./a.out 5
  real    0m11.064s
  $ gcc -O2 uint.c -DLONG -DSAT -DMULT; time ./a.out 5
  real    0m1.886s
  $ gcc -O2 uint.c -DLONG -DNOSAT -DMULT; time ./a.out 5
  real    0m1.035s

that the slight slowdown on MIPS is a minor sacrifice:

  $ cc uint.c -O2 -DLONG -DDOUBLESAT -DMULT; time ./a.out 10
  real    0m1.723s
  $ cc uint.c -O2 -DLONG -DSAT -DMULT; time ./a.out 10
  real    0m2.209s

which is outweighed by the gains in other operations:

  $ cc uint.c -O2 -DLONG -DDOUBLESAT -DADD; time ./a.out 10
  real    0m1.783s
  $ cc uint.c -O2 -DLONG -DSAT -DADD; time ./a.out 10
  real    0m0.654s
  $ cc uint.c -O2 -DLONG -DNOSAT -DADD; time ./a.out 10
  real    0m0.418s


Also, the LONGLONG case should be changed regardless since
casting to a double loses precision.

- Paul