mORMot Open Source

louis_riviera

Member

Registered: 2013-09-23

Posts: 61

Random()

Is there an alternative for this RTL random generator? It is not very fast or accurate.

An SSE optimized version would be nice but i cannot find any in SynCommons.pas

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,682

Website

Re: Random()

There is none in SynCommons.pas.

Up to now, we rely on Random() + GetTickCount for instance as RandomSeed().
It is enough for our purpose.
Then a hash (e.g. crc32 or SHA256) if real random is needed.

I suspect this implementation is pretty good and fast:
https://code.google.com/p/gpdelphiunits … domGen.pas

louis_riviera

Member

Registered: 2013-09-23

Posts: 61

Re: Random()

Random() is not thread safe at all. Because it is not a thread var. Plus 64 bit is a lot slower since its written in ASM.

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,682

Website

Re: Random()

You have to protect your call to Random(), or the code supplied at https://code.google.com/p/gpdelphiunits … domGen.pas with a critical section.

louis_riviera

Member

Registered: 2013-09-23

Posts: 61

Re: Random()

Is better to use threadvar IMHO. Locks are slower, much slower.