| Type | Issue | Status | complete | Date | 2-Jun-2009 08:20 |
|---|---|---|---|---|---|
| Version | alpha 55 | Category | n/a | Submitted by | Ladislav |
| Platform | All | Severity | minor | Priority | urgent |
| Summary | RANDOM documentation necessary |
|---|---|
| Description |
TomC wrote: For homework, I was asked about the random number generator in my favorite language ... did some experiments but answered "closed source" to what "algorithm does it use?" for this part, I got a zero. So, could someone with access to rebol source or internal doc get me information on the algorithms for 'random and 'random/secure they are probably some flavor of linear congruent generators (please don't say RANDU) but multiplicative? or mixed? maybe a PMMLCG? shuffling? QCG? MRG? What constants are used? what is the period? how many streams? |
| Example code |
Answer: currently, there are two primary random generators: 1. old method, high speed, simple multiplicative: next = next * 1103515245L + 12345L; tmp = next & 0xffff0000; next = next * 1103515245L + 12345L; tmp |= (next >> 16); 2. much slower, SHA1() of a repeating pattern of the integer bytes (20 bytes total). If you want others, post them (as long as BSD or MIT license). |
| Assigned to | n/a | Fixed in | - | Last Update | 20-Jun-2009 20:27 |
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| Comments | |
|---|---|
|
(0000892)
Ladislav 2-Jun-2009 08:22 |
Tom offers to examine the source, if sent to him privately to extract the implementation specifications. |
|
(0000918)
Ladislav 9-Jun-2009 20:49 |
I would say, that it may be marked as complete, the description incorporated into http://www.rebol.com/r3/docs/functions/random.html |
| Date | User | Field | Action | Change |
|---|---|---|---|---|
| 20-Jun-2009 20:27 | Ladislav | Status | Modified | built => complete |
| 9-Jun-2009 20:50 | Ladislav | Status | Modified | waiting => built |
| 9-Jun-2009 20:49 | Ladislav | Comment : 0000918 | Added | - |
| 2-Jun-2009 19:43 | carl | Code | Modified | - |
| 2-Jun-2009 19:43 | carl | Status | Modified | reviewed => waiting |
| 2-Jun-2009 16:38 | BrianH | Status | Modified | submitted => reviewed |
| 2-Jun-2009 16:38 | BrianH | Type | Modified | Bug => Issue |
| 2-Jun-2009 08:25 | Henrikmk | Summary | Modified | Random documentation necessary => RANDOM documentation necessary |
| 2-Jun-2009 08:23 | Ladislav | Description | Modified | - |
| 2-Jun-2009 08:22 | Ladislav | Comment : 0000892 | Added | - |
| 2-Jun-2009 08:20 | Ladislav | Ticket | Added | - |