On 13/04/16 02:07, Yuyang Du wrote: > On Tue, Apr 12, 2016 at 11:14:13AM +0100, Juri Lelli wrote: > > On 12/04/16 03:12, Yuyang Du wrote: > > > On Mon, Apr 11, 2016 at 11:41:28AM +0100, Juri Lelli wrote: > > > > Hi, > > > > > > > > On 11/04/16 06:36, Yuyang Du wrote: > > > > > __compute_runnable_contrib() uses a loop to compute sum, whereas a > > > > > table loopup can do it faster in a constant time. > > > > > > > > > > The following python script can be used to generate the constants: > > > > > > > > > > print " #: yN_inv yN_sum" > > > > > print "-----------------------" > > > > > y = (0.5)**(1/32.0) > > > > > x = 2**32 > > > > > xx = 1024 > > > > > for i in range(0, 32): > > > > > if i == 0: > > > > > x = x-1 > > > > > xx = xx*y > > > > > else: > > > > > x = x*y > > > > > xx = int(xx*y + 1024*y) > > > > > print "%2d: %#x %8d" % (i, int(x), int(xx)) > > > > > > > > > > print " #: sum_N32" > > > > > print "------------" > > > > > xxx = xx > > > > > for i in range(0, 11): > > > > > if i == 0: > > > > > xxx = xx > > > > > else: > > > > > xxx = xxx/2 + xx > > > > > print "%2d: %8d" % (i, xxx) > > > > > > > > > > > > > Thanks for the script, really useful. Do you think there is value in > > > > making it general? Like if we want to play with/need changing LOAD_AVG_ > > > > PERIOD in the future to something different than 32. > > > > > > i think a s/32/xx/ should work. > > > > > > > Also, does the following assume LOAD_AVG_PERIOD == 32? And if yes, do > > > > you think there is any value in removing that assumption? > > > > > > Like Peter said, we are heavily dependent on it already. > > > > But I think the current code should still work if we define LOAD_AVG_ > > PERIOD as, say, 16 and we use Paul's program to recompute the tables. > > > > My point was about trying to keep everything related to LOAD_AVG_PERIOD > > and not start assuming it is 32. I'm not saying your changes assume > > that, I was asking if they do. > > Oh, then my changes do not make more or less dependency. The entire avg thing > should only have two seeds (and all others depend on them): > > (1) a period is 1024*1024ns
Which I think is fine. > (2) a half-life is 32 periods > And this is fine as well, but only if we can actually write (2) a half-life is LOAD_AVG_PERIOD periods Best, - Juri > I'll check if there is anything hard-coded other than the two. >
