Zipf distributed random variates.

Zipf distributed random variates.

[rsc, 2009-12-14 03:13:10]

looks pretty good.
a few minor nits.

http://codereview.appspot.com/176070/diff/1/3
File src/pkg/rand/zipf.go (right):

http://codereview.appspot.com/176070/diff/1/3#newcode14
src/pkg/rand/zipf.go:14: // A Zipf generates Zipf distributed variates
period at end of sentence

http://codereview.appspot.com/176070/diff/1/3#newcode52
src/pkg/rand/zipf.go:52: // Initialize a Zipf so that variates p(k) are
generated on [0, imax]
should be a sentence.

NewZipf returns a Zipf generating p(k) on [0, imax] 
proportional to (v+k)**(-s) where s>1, k>=0, and v>=1.

(I added the v >= 1.)

http://codereview.appspot.com/176070/diff/1/3#newcode57
src/pkg/rand/zipf.go:57: if v == 0 {
So v == 0 is okay but other v < 1 is not?
Seems cleaner to require v >= 1 and drop this,
but I don't know what the usages are like.

http://codereview.appspot.com/176070/diff/1/3#newcode60
src/pkg/rand/zipf.go:60: if z.init(r, s, v, imax) {
might as well inline the init call since it is not
used elsewhere.

http://codereview.appspot.com/176070/diff/1/3#newcode69
src/pkg/rand/zipf.go:69: var k = float64(0.0);
s/var k =/k :=/

http://codereview.appspot.com/176070/diff/1/3#newcode78
src/pkg/rand/zipf.go:78: } else if ur >=
z.h(k+0.5)-math.Exp(-math.Log(k+z.v)*z.q) {
no need for else since the if broke.

}
if ur >= ...

(or use || above)

[rsc, 2009-12-16 05:05:11]

looks good to me; thanks.

[rsc, 2009-12-16 05:10:28]

LGTM

When you hg sync you're going to get a merge
conflict because I've stripped the semicolons
with hg gofmt.  You'll be able to resolve it with

cd $GOROOT/src/pkg/rand
hg revert zipf.go
hg resolve -m zipf.go  # marks it resolved

[rsc, 2009-12-16 05:10:39]

*** Submitted as http://code.google.com/p/go/source/detail?r=230b42431917 ***

rand: Zipf distributed random variates.

R=rsc
http://codereview.appspot.com/176070

Committer: Russ Cox <rsc@golang.org>