Java-Gaming.org Hi !
Featured games (90)
games approved by the League of Dukes
Games in Showcase (767)
Games in Android Showcase (230)
games submitted by our members
Games in WIP (854)
games currently in development
News: Read the Java Gaming Resources, or peek at the official Java tutorials
 
    Home     Help   Search   Login   Register   
Pages: 1 ... 4 5 [6]
  ignore  |  Print  
  Generalized Rant Thread  (Read 66545 times)
0 Members and 1 Guest are viewing this topic.
Offline Roquen

JGO Kernel


Medals: 518



« Reply #150 - Posted 2013-03-27 16:27:25 »

Sigh:  Know your math kids.  I was peeking around at skip lists to see if I could find a "search finger" version to test out in a given situation I have.  No luck, but I glanced at quite of few skip list implementations and what struck me is:  people don't know their math.  A classic skip list needs to generate some "levels" with probabilities of : 50%, 25% 12.5%, etc.  The 'fastest' way this seems to be commonly done (in java-speak) is:

(int)(Math.log(1.-rng.nextDouble())/Math.log(0.5))

and quite of few do it iteratively. Doh!!  This can be cheaply be computed as follows:

Integer.numberOfLeadingZeros(rng.nextInt())

Why? Top bit has a 50% chance of being zero, and likewise for all following bits.  So having two zeros in a row is: 0.52 and likewise for n-zeros is 0.5n.  End of story.  (NOTE: leading zero counts are intrinsic and directly map to a hardware instruction in HotSpot)
Pages: 1 ... 4 5 [6]
  ignore  |  Print  
 
 

 
EgonOlsen (1327 views)
2018-06-10 19:43:48

EgonOlsen (1195 views)
2018-06-10 19:43:44

EgonOlsen (928 views)
2018-06-10 19:43:20

DesertCoockie (1329 views)
2018-05-13 18:23:11

nelsongames (1109 views)
2018-04-24 18:15:36

nelsongames (1349 views)
2018-04-24 18:14:32

ivj94 (2084 views)
2018-03-24 14:47:39

ivj94 (1242 views)
2018-03-24 14:46:31

ivj94 (2241 views)
2018-03-24 14:43:53

Solater (802 views)
2018-03-17 05:04:08
Deployment and Packaging
by mudlee
2018-08-22 18:09:50

Java Gaming Resources
by gouessej
2018-08-22 08:19:41

Deployment and Packaging
by gouessej
2018-08-22 08:04:08

Deployment and Packaging
by gouessej
2018-08-22 08:03:45

Deployment and Packaging
by philfrei
2018-08-20 02:33:38

Deployment and Packaging
by philfrei
2018-08-20 02:29:55

Deployment and Packaging
by philfrei
2018-08-19 23:56:20

Deployment and Packaging
by philfrei
2018-08-19 23:54:46
java-gaming.org is not responsible for the content posted by its members, including references to external websites, and other references that may or may not have a relation with our primarily gaming and game production oriented community. inquiries and complaints can be sent via email to the info‑account of the company managing the website of java‑gaming.org
Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines | Managed by Enhanced Four Valid XHTML 1.0! Valid CSS!