<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><br><div><div>On Jul 2, 2014, at 1:27 PM, Nick Lewycky <<a href="mailto:nlewycky@google.com">nlewycky@google.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On 2 July 2014 11:52, Chandler Carruth <span dir="ltr"><<a href="mailto:chandlerc@google.com" target="_blank">chandlerc@google.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div><br><div class="gmail_quote">On Tue, Jul 1, 2014 at 9:50 PM, Chris Lattner <span dir="ltr"><<a href="mailto:clattner@apple.com" target="_blank">clattner@apple.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Any thoughts guys? If we are unclear what the right design here is, I'd prefer you to revert the patch until it is figured out.</blockquote>
</div><br></div>I'm moderately confident this isn't the right design...</div><div class="gmail_extra"><br></div><div class="gmail_extra">Specifically, I totally get why the seed and salt data needed by an RNG might be in the module (preferably opaquely in module-level metadata or something), but I don't really understand why the RN*G* would be in the module rather than in the pass or thing which is generating the random data for some purpose.</div>
</div></blockquote><div><br></div><div>Chandler and I just had a talk about this and formed some amount of consensus that I want to relay to the list.</div><div><br></div><div>The RNG should have a seed in the module that we can use to create the RNG as needed. For predictability we agreed on MT19937 which has a lot of good properties (well-balanced, doesn't have a warmup period, etc). Module-level metadata works well for storing the seed.</div>
<div></div><div><br></div></div></div></div></blockquote><br><blockquote type="cite"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><div>Stephen and Chris, does this work for both of you? Are the motivations behind this design clear?<br>
</div>
</div></div></div></blockquote><br></div><div>Storing this as module-level metadata makes sense to me.</div><div><br></div><div>-Chris</div><br></body></html>