Hi Tomas, last year we had this discussion:
On Thu, Apr 02, 2009 at 09:20:57AM +0100, Tomas Hlavaty wrote: > Hi Alex, > > > However, I am aware of the fact that in picoLisp the printing of > > numeric results is often much more expensive than the actual > > calculations, due to the conversions necessary for the decimal base. > > > If I take out the final (prinl Y) from gmp-test2.l, I get: > > It makes a considerable difference. > > Interesting, it does not seem to make much difference with the C > version when I take the final 'printf' out of the C code. Now, while playing with the task "Arbitrary-precision integers" at www.rosettacode.org (** 5 (** 4 (** 3 2))) I hit upon that problem again. While the actual calculation takes only a fraction of a second (the '->' prompt appears), formatting the decimal output (183231 digits) takes 634 seconds on the 64-bit version. Again, this bothered me, and I investigated a little deeper. The bottleneck is the binary-to-decimal conversion. PicoLisp uses for that an algorithm with binary code digits. It consists of a nested loop, where the innter loop manipulates BCD-bytes with shifts and additions (no divisions). It occurred to me that this could be sped up considerably with using larger "digits". So I rewrote it, so that a single BCD digit is no longer a byte, but a complete word, holding 9 BCD digits on 32 bits, and 18 digits on 64 bits. This helped a lot! The 634 seconds reduced to 37 seconds, a 17-fold speed improvement :-) Cheers, - Alex -- UNSUBSCRIBE: mailto:picol...@software-lab.de?subject=unsubscribe
