FFT Multiplication (HP-48G/GX/G+)

[Gerson W. Barbosa]

(02-11-2014 09:04 AM)Raymond Del Tondo Wrote:  Hi,

(02-10-2014 10:02 PM)Gerson W. Barbosa Wrote:  Two 256-digit numbers, actually, giving a 512-digit result. Sorry for the mistake.

You could speed up things by trying to avoid object type changes where possible.

The snippet below shows some time-consuming actions from your code.

(02-10-2014 10:02 PM)Gerson W. Barbosa Wrote:  

Code:


  START 0 +
  NEXT SWAP ROT 1
ROT
  START 0 +
  NEXT 

OBJ\-> 

1 \->LIST

\->ARRY

If you work with arrays anyway, you could try to avoid building lists. Creating and decomposing lists is very time-consuming.
If possible, meta obs are recommended.

Thanks for your tips!

I'd rather use vectors only, but lists are more convenient for certain tasks (or I just don't know how to do them using vectors).

(02-11-2014 09:04 AM)Raymond Del Tondo Wrote:  I didn't dive into the code too deeply, but I'm sure the functionality can be made faster on an HP 48GX than any code giving the same results on an HP-71B;-)

I was disappointed with the HP-48GX, but now I see I can blame it on my sloppy adaptation. It surely can do better than this:

# Groups Digits (results) Time 71B Time 48GX
16 128 24.11 14.39
32 256 53.41 40.95
64 512 116.74 199.96

Also, I suspect the performance decrease as the number of digits grow is due to lack of memory, as I have only 12 K left (and only one HP-48GX).

Regards,

Gerson.