Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Okay, answer #2 ;-)</p> <p>I am going to say ... keep it simple. Just use a "short" seed to prime the MT (imagine that this seed is 2<sup>32</sup> bits for lack of better restriction). This assumes that the the short seed generates "sufficiently distributed" MT starting states (e.g. <code>init_genrand</code> in the code in my other answer, hopefully). This doesn't guarantee an equally distributed starting state but rather goes for "good enough", see below.</p> <p>Each node will use it's own sequence of seeds which are pre-selected (either a list of random seeds which is transmitted or a formula like <code>number_nodes * node_number * iteration</code>). The important thing is that the initial "short" seed <em>will never be re-used across nodes</em>.</p> <p>Each node will then use a MT PRNG initialized with this seed <code>n</code> times where <code>n &lt;&lt;&lt; MT_period / max_value_of_short_seed</code> (<a href="http://www.quadibloc.com/crypto/co4814.htm" rel="nofollow">TT800 is 2<sup>800</sup>-1 and MT19937 is 2<sup>19937</sup>-1</a>, so <code>n</code> can still be a <em>very large</em> number). After <code>n</code> times, the node moves onto the next seed in the chosen list.</p> <p>While I do not (nor can I) provide a "guarantee" that no node will ever have a duplicate sequence at the same time (or at all), here is what <a href="http://developer.amd.com/libraries/acml/onlinehelp/Documents/Using-Different-Seeds.html" rel="nofollow">AMD says about Using Different Seends</a>: (Obviously the initial seeding algorithm plays a role).</p> <blockquote> <blockquote> <p><strong>Of the four methods for creating multiple streams described here, this is the least satisfactory</strong> ... For example, sequences generated from different starting points may overlap if the initial values are not far enough apart. The potential for overlapping sequences is reduced if the period of the generator being used is large. <strong>Although there is no guarantee of the independence of the sequences, due to its extremely large period, using the Mersenne Twister with random starting values is unlikely to lead to problems</strong>, especially if the number of sequences required is small ...</p> </blockquote> </blockquote> <p>Happy coding.</p>
    singulars
    1. This table or related slice is empty.
    1. POPseudo-random number generator for cluster environment
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThe four solutions proposed by AMD are true only in their library case. But when you're dealing with the original MT implementation, like @Charles Brunet does, parameterization through Dynamic Creator is the most appropriate way to handle independent Mersenne Twister streams.
      singulars
      1. PO
      1. USjopasserat
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload