Rethinking race-free process signaling

Posted Apr 5, 2019 13:03 UTC (Fri) by corbet (editor, #1)
In reply to: Rethinking race-free process signaling by mezcalero
Parent article: Rethinking race-free process signaling

That's the four million mentioned in the text; it is indeed explicitly capped at that size.

to post comments

Rethinking race-free process signaling

Posted Apr 5, 2019 13:44 UTC (Fri) by mezcalero (subscriber, #45103) [Link] (3 responses)

Ah, indeed, I read 4 billion when you correctly wrote 4 million, and in my mind 2^32 formed. Ignore me then. Sorry for the confusion. Still weird though that this is capped at 2^22. (And the MAXINT reference is misleading still, as you couldn't set that without reworking the kernel substantially.)

Rethinking race-free process signaling

Posted Apr 11, 2019 14:35 UTC (Thu) by kmweber (guest, #114635) [Link] (2 responses)

> Still weird though that this is capped at 2^22.

So on an unrelated topic, but similar issue...years ago, the Madden series of American football games had a hard limit of 255 points that could be scored in a game and 1023 rushing yards that could be gained (I assume other stats were similarly capped, but these were the ones I noticed) (these limits may or may not still be there, it's been years since I played). For those of you who aren't familiar with American football, those numbers are ridiculously unachievable in any real game, but when playing the video game on easy settings it's quite plausible to reach both of those limits by halftime (particularly with skillful clock management--in short, American football rules specify that whether or not the game clock keeps running between plays is generally contingent upon the outcome of the just-completed play, with some complications for timeouts, penalties, and injuries, and when the end of the half or game is near--manipulating these rules with play-calling is a crucial part of late-game strategy). The 255-point limit was annoying but straightforward enough to understand, but for the life of me I couldn't understand why accumulated rushing yards was limited at 1023. This was in the mid-to-late 2000s; it wasn't *that* long ago, and memory certainly wasn't scarce enough that it was worth the extra trouble of using bitfields or implementing an explicit limit in code that was less than the max value of the data type used.

Now that I think of it, maybe this is where those extra ten bits from the PID cap went :)

Rethinking race-free process signaling

Posted May 6, 2019 18:25 UTC (Mon) by mgedmin (guest, #34497) [Link] (1 responses)

> The 255-point limit was annoying but straightforward enough to understand, but for the life of me I couldn't understand why accumulated rushing yards was limited at 1023. This was in the mid-to-late 2000s; it wasn't *that* long ago, and memory certainly wasn't scarce enough that it was worth the extra trouble of using bitfields or implementing an explicit limit in code that was less than the max value of the data type used.

16-bit fixed point numbers maybe, with 6 bits reserved for the fractional value?

Rethinking race-free process signaling

Posted Sep 5, 2019 21:43 UTC (Thu) by kmweber (guest, #114635) [Link]

There is no fractional member. American football statistics are counted in whole numbers, and the game reflected that.

Essentially, the number of yards you've gained is equal to the number of yard lines you've crossed. So if you start from barely past the one yard line and get to just short of the four yard line, you've only officially gained two yards for statistics purposes even though you've actually gained very nearly three. And on the flip side, if you start from just short of the two yard line and end just past the three yard line, you're credited with a two-yard gain even though you've really covered barely more than one.