[Numpy-discussion] What is consensus anyway

Charles R Harris charlesr.harris@gmail....
Sun Apr 22 19:04:34 CDT 2012

On Sun, Apr 22, 2012 at 4:15 PM, Nathaniel Smith <njs@pobox.com> wrote:

> If you hang around big FOSS projects, you'll see the word "consensus"
> come up a lot. For example, the glibc steering committee recently
> dissolved itself in favor of governance "directly by the consensus of
> the people active in glibc development"[1]. It's the governing rule of
> the IETF, which defines many of the most important internet
> standards[2]. It is the "primary way decisions are made on
> Wikipedia"[3]. It's "one of the fundamental aspects of accomplishing
> things within the Apache framework"[4].
> [1] https://lwn.net/Articles/488778/
> [2] https://www.ietf.org/tao.html#getting.things.done
> [3] https://en.wikipedia.org/wiki/Wikipedia:Consensus
> [4] https://www.apache.org/foundation/voting.html
> But it turns out that this "consensus" thing is actually somewhat
> mysterious, and one that most programmers immersed in this culture
> pick it up by osmosis. And numpy in particular has a lot of developers
> who are not coming from a classic FOSS programmer background! So this
> is my personal attempt to articulate what it is, and why requiring
> consensus is probably the best possible approach to project decision
> making.
> So what is "consensus"? Like, voting or something?
> -----------------------------------------------------
> This is surprisingly subtle and specific.
> "Consensus" means something like, "everyone who cares is satisfied
> with the result".
> It does *not* mean
> * Every opinion counts equally
> * We vote on anything
> * Every solution must be perfect and flawless
> * Every solution must leave everyone overjoyed
> * Everyone must sign off on every solution.
> It *does* mean
> * We invite people to speak up
> * We generally trust individuals to decide how important their opinion is
> * We generally trust individuals to decide whether or not they can
> live with some outcome
> * If they can't, then we take the time to find something better.
> One simple way of stating this is, everyone has a veto. In practice,
> such vetoes are almost never used, so this rule is not particularly
> illuminating on its own. Hence, the rest of this document.
> What a waste of time! That all sounds very pretty on paper, but we
> have stuff to get done.
> -----------------------------------------------------------------------------------
> First, I'll note that this seemingly utopian scheme has a track record
> of producing such impractical systems as TCP/IP, SMTP, DNS, Apache,
> GCC, Linux, Samba, Python, ...
Linux is Linus' private tree. Everything that goes in is his decision,
everything that stays out is his decision. Of course, he delegates much of
the work to people he trusts, but it doesn't even reach the level of a
BDFL, it's DFL. As for consensus, it basically comes down to convincing the
gatekeepers one level below Linus that your code might be useful. So bad
example. Same with TCP/IP, which was basically Kahn and Cerf consulting
with a few others and working by request of DARPA. GCC was Richard Stallman
(I got one of the first tapes for a $30 donation), Python was Guido. Some
of the projects later developed some form of governance but Guido, for
instance, can veto anything he dislikes even if he is disinclined to do so.
I'm not saying you're wrong about open source, I'm just saying that that
each project differs and it is wrong to imply that they follow some common
form of governance under the rubric FOSS and that they all seek consensus.
And they certainly don't *start* that way. And there are also plenty of
projects that fail when the prime mover loses interest or folks get tired
of the politics.

But mere empirical results are often less convincing than a good
> story, so I will give you two. Why does a requirement for consensus
> work?
> Reason 1 (for optimists): *All of us are smarter than any of us.* For
> a complex project with many users, it's extraordinarily difficult for
> any one person to understand the full ramifications of any decision,
> particularly the sort of far-reaching architectural decisions that are
> most important. It's even more difficult to understand all the
> possibilities of all the different possible solutions. In fact, it's
> *extremely* common that the correct solution to a problem is the one
> that no-one thinks of until after a month of annoying debate. Spending
> a month to avoid an architectural problem that will haunt us for years
> is an *excellent* trade-off, even if it feels interminable at the
> time. Even two months. Usually disagreements are an indication that a
> better solution is possible, even when it's not clear what that would
> be.
> Reason 2 (for pessimists): *You **will** reach consensus sooner or
> later; it's less painful to do up front.* Example: NA handling. There
> are two schemes that people use for this right now -- numpy.ma and
> ugly NaN kluges (see e.g. nanmean). These are generally agreed to be
> suboptimal. Recently, two new contenders have shown up: the NEP
> masked-NA support currently in master, and the unrelated NA support in
> pandas (which as a library is attracting a *lot* of the statistical
> analysis folk who care about missing data, kudos to Wes). I think that
> right now, the most likely future is that a few years from now, many
> people will still be using the old solutions, and others will have
> switched to the new (incompatible) solutions, and we will have *4*
> suboptimal schemes in concurrent use. If (when) this happens, we will
> have to re-open this discussion yet again, but now with a heck of a
> mess to clean up. This is FOSS -- if people aren't convinced by your
> solution, they will just ignore it and do their own thing. So a policy
> that allows changes to be made without consensus is a recipe for
> entrenching disagreements and splitting the community.
> Okay, great, but even if it's the best thing ever, we *can't* hold a
> vote on every change! What are you actually suggesting we do?
> ----------------------------------------------------------------------------
> Right, that's not the idea. Most changes are pretty obviously
> uncontroversial, and in fact we usually have the opposite problem --
> it's hard to get people to do code review!
> So having consensus on every change is an ideal, and in practice, just
> following the reasonable person principle lets us get pretty close to
> that ideal. If no-one objects to a change, then it's probably fine.
> (And it's not like anyone *wants* that segfault to remain unfixed!
> That's obvious.) OTOH, this isn't an excuse to try gaming the system
> -- if you have a change that might affect people adversely, then it
> can be worthwhile to send them a ping, even if they didn't object.
> They might have just missed seeing it go by, and if it's going to be a
> problem, better to find out now!
> In fact, one of the nice things about having a consistent culture of
> consensus-building is that people learn to trust that if they do have
> a problem, it will be taken seriously. And that, in turn, makes it
> okay to make judgement calls about whether the participants in some
> discussion basically agree, or whether the apparent disagreement is
> just bikeshedding[1], or whatever. If you make the wrong judgement
> call, then someone will tell you, and no harm is done. If you do not
> have such a culture, then people may (will) despair of being taken
> seriously, and go do something more pleasant and productive, like
> fire-walking or coding in Matlab.
> [1] http://producingoss.com/en/common-pitfalls.html#bikeshed
> So mainly what I'm saying we should do is:
> 1. Make it as easy as possible for people to see what's going on and
> join the discussion. All decisions and reasoning behind decisions take
> place in public. (On this note, it would be *really* good if pull
> request notifications went to the list.)
> 2. If someone raises a substantive objection, take that seriously.
> 3. If someone says "no, this is just not going to work for me,
> because... <something substantive here>", then it can't go in.
What happens when someone wants to spend all their time talking about
process? It can get kind of old.

> It turns out that since we are all human, it's much easier to take
> people's concerns seriously when you know that they can veto your
> code! The result is that in practice, disagreements get resolved at
> point (2) there, and no-one feels the need to take such extreme
> measures as vetoing anything. I'm as lazy as anyone else; I produce
> better solutions when I'm forced to keep looking for them.
So if we just follow this consensus stuff, everything will be perfect?
> ---------------------------------------------------
> Ha ha ha no. It can and does work better than any other options I'm
> aware of, but it takes practice and there are certainly still failure
> modes. Here's some that come to mind:
> * Bikeshedding: Mentioned above. There's nothing *wrong* with everyone
> speaking up to voice their opinion, but it shouldn't be an obstacle to
> getting work done when in fact everyone will be satisfied regardless.
> * False compromise: if all you're trying to do is make everybody
> happy, then it's easy to end up with a "compromise" that takes one bit
> from each proposal (or simply takes the union of them all). This is
> usually worse than any of the original proposals. Good designs take
> work; skipping that work is tempting; resist it.
> You also can end up with some surprising solutions, e.g.:
> * The group reaches consensus that the problem is well understood and
> there simply is no perfect solution, but something is better than
> nothing. So everyone agrees to, in effect, flip a coin. (Example: the
> Python ternary operator)
> * The group reaches consensus that while other points of view may be
> valid, this project only has room for one of them, sorry, anyone who
> disagrees will have to start their own project. (Example: GPL versus
> BSD debates)
> * The group reaches consensus that at least one piece of a larger
> proposal is okay to start, which puts off the show-down over the rest
> of it until another day. (At which point more data more be available,
> opinions may have changed, or the whole issue may have become
> irrelevant.)
> Remember, the goal is always to find some way forward that we can
> collectively live with. Sometimes you can successfully convince
> everyone of the intrinsic awesomeness of your original idea through
> argument along... but clever outside-the-box proposals often pay-off
> too.
> But what about obstructive people abusing their veto power?
> ----------------------------------------------------------------
> This concern makes perfect sense, but it turns out to just not be as
> much of a problem as often as you'd think. Most people have more
> interesting things to do with their lives than to gum up the mailing
> list for some random software library. It's a fair assumption that if
> someone cares enough to speak up, it's because they have some
> legitimate interest in numpy's future. And again, energy spent on
> trying to sniff out obstructionists can usually be more profitably
> spent on finding better solutions.
> That said, yes, sometimes people may be obstructive or act in bad
> faith. Here's some good experience-based advice on this:
>  http://producingoss.com/en/difficult-people.html
> Notice that everything they say is still oriented around consensus --
> "You may not persuade the person in question, but that's okay as long
> as you persuade everyone else", "a perfect example of how to build a
> strong case on neutral, quantitative data", the "masterful strategy"
> is to build consensus before acting. The consensus ideal is perfectly
> compatible with dealing with difficult people.
> Other documents
> ---------------------
> Like I said at the start, this is just my attempt to distill some
> abstract principles from my own experience. I can't take credit for
> most of these insights, and no doubt I've articulated some of them
> poorly. Fortunately, we don't all have to agree on every detail to get
> things done :-). But if you want to read more about this topic, and
> from other perspectives, here are some decent documents:
>  http://producingoss.com/en/consensus-democracy.html
>  https://www.ietf.org/tao.html#getting.things.done
>  https://en.wikipedia.org/wiki/Consensus_decision-making
> And, of course, I would love to hear feedback on this document!
It seems top heavy for an organization that has maybe three people working
on Numpy C code in their spare time. I think the ideal here would be for
someone to produce their own version as a working example and then we could
discuss merging code, and also have something to play with.

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