Am 07.12.2011 16:03, schrieb Graeme Geldenhuys: > On 7 December 2011 14:54, Jonas Maebe <jonas.maebe@....> wrote: >> >> That's correct. We use the mersenne twister, Delphi probably a linear >> congruential generator. The mersenne twister has a much larger period. > > I was reading a bit more about this. The Mersenne Twister (MT) > generator has a massive period of 2^19937−1, compared to the XorShift > generator, which in turn has a period of 2^128-1. > > Most text I read mentions that MT is great for statistical purposes, > and performs well in its class. > > So wouldn't it maybe make more sense to let the standard (read more > common) Random() call use a higher performance random number > generator, with a much lower period.
Well, once we thought we try to do things better than Delphi ;) Some people, I think John Lee, asked for a better random in FPC years ago so Jonas implemented a MT. > Then add the MT generator as a > call to the Maths unit - where more statistical functions are located? > > Most applications are not statistical apps, they just want a random > number here or there, so such high period low performance generator is > normally not required. Having it in the Maths unit still makes in > available when needed though - for those specialised apps. > > Just a thought... > FPC uses MT at least for 10 years and nobody complained about performance yet. So I suspect the cases might be very rare when random performance matters and having good random numbers is always a good thing ... I prefer not to change it but it's fine for me for delphi compatibility's sake ;) _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
