[user49598]

I think this is one of those problems where smart people think too hard. It has nothing to do with non engineers misunderstanding randomness or the human mind intrinsically superimposing structure. All it has to do with is being an algorithmic dj.

Users don't want a random playlist. They want their songs shuffled, and they want them shuffled in a way that keeps songs from the same album distributed far apart. No one presses the shuffle button to get satisfaction out of pure randomness. They press the button because they want to listen to music. If think your users are dumb because they don't understand randomness then you don't understand the job that shuffle is supposed to do.

[mapgrep]

Did you read the first (highest rated) answer? This has nothing to do with iTunes trying to be "an algorithmic DJ" rather than truly random, it has do with the confusing intersection of two features: You can pick the first song in the randomly "shuffled" playlist, and a shuffled playlist holds its order until it is re-shuffled.

The user posting the question assumed that when he double-clicked on the first song in the playlist, iTunes was re-shuffling the playlist. It wasn't. It assumed he wanted to start the playlist again. If he had picked any other song to double click after playback was stopped, it would have re-shuffled the playlist.

The solution was to toggle shuffle off and then on again. Then he'd force re-shuffling.

iTunes does have a separate algorithmic DJ feature, by the way, called iTunes DJ. No need to mess up shuffle. Shuffle is truly random.

[dpark]

> If he had picked any other song to double click after playback was stopped, it would have re-shuffled the playlist.

Pretty sure that's not the case, and the answer indicated otherwise. The order is stable until it's explicitly reshuffled.

[mapgrep]

I was mis-remembering how iTunes work there. It will auto-re-shuffle in some cases -- you don't always have to do it explicitly -- but it looks like it has more to do with whether you switch away from the playlist after the music stops playing. If I simply "pause" and select another song, without switching away, the order remains stable as you say. If I switch to say the Music library view, and then back, and double click a song (any song), it re-shuffles with that double-clicked song on top, playing.

[jvm]

That was part of the incorrect opinion parent was saying the user had.

[dbbolton]

Leonard Mlodinow touches on this issue in The Drunkard's Walk[1]. If I remember correctly, his explanation was something along the lines of this: a truly random playlist is not desirable to most users, which challenges the claim "I do believe the ordering is truly random the first time it's generated" in the top answer. Mlodinow explains that most people really don't understand randomness, and a "truly random" playlist might have the same song twice in a row, play a few songs from the same album in the normal order, and things like that. Some people don't realize that rolling 1,2,3,4,5,6 on a die in order is as likely as 6,4,1,2,5,3 even though the second set of outcomes might seem more likely because it looks more random. To outcount for this, iTunes actually does use an algorithm to make the shuffled playlist "better" than a truly random one.

Of course, by some definitions, even rand() isn't random enough, so I can see why people argue about it. The book doesn't even provide a rigorous definition of the concept, but it was never intended to be a serious treatise on statistics.

1. http://www.nytimes.com/2008/06/08/books/review/Johnson-G-t.h...

[drostie]

This.

I have been dealing with Samsung half-phone half-MP3 players for a while now, and they all choose the next track randomly. I pine for the days when I used to have an iPod that could run Rockbox, so that the "back" and "forward" functions worked in the shuffled playlist. Sometimes I mean "rewind to start" and I accidentally tap the button twice to say "seek to last track." That takes me to a random track and then the original is no longer available as "next". So irritating.

And this randomness-is-too-random crap does happen. I'll put on a list of songs to sing along to, only a few hundred songs, and often after half an hour or an hour I'll be repeating songs which I've already sung. Sometimes they'll be two-in-a-row or separated by only one, two, or three different songs.

(The other great thing about Rockbox was that I had access to folders which automatically acted like playlists. We've had debates about this back and forth around HN, I know, but suffice it to say that it's really nice to have an "Audiobooks" folder where you can download individual book folders. Otherwise you often have to make sure that you don't get bizarre interleaved numberings, chapter 01 from book X followed by chapter 01 from book Y. In Samsung, this is actually governed by the Title of the ID3 tag of the MP3, which can be even worse.

[kstenerud]

This is something any game programmer can tell you. Pure randomness in a game kills the fun. You have to shape the randomness to match human expectation.

[pmelendez]

That depends on the game and the feature of the game that requires the randomness though. True... pure randomness over spawning points for enemies in an action rpg game, might kill the experience. But if I am playing poker.. I do expect something close to pure randomness when you are dealing my cards.

[klodolph]

I think people are confusing the term "true random". It's still truly random, but it won't have a uniform distribution over all possible values. For example, a common trick in FPS games is to pick a random spawn point, but exclude spawn points that are too close to other players. Still truly random.

Another trick in RPGs is to increase or decrease the odds of a successful hit according to recent hits and misses, bringing the short-term average much closer to the expected value. It's still "true random", but uses correlation between attacks to create an underdispersed distribution overall. (Basically, you want to make the variance lower to make people happy.)

[zeroonetwothree]

"Truly random" is usually contrasted with "pseudorandom". In that sense almost all games are not "truly random". But you are right in that "truly random" also doesn't mean "uniform".

[ubernostrum]

A lot depends on the game.

Example: My hobby is that I'm a tournament judge for Magic: the Gathering. I also play a bit, because I like the game. And there's an online version... which has a shuffling system that's actually random (i.e., has reportedly been examined by the same folks who certify stuff for casinos, and passed).

But that causes a lot of complaining from players, because real random shuffling is very different from what human beings accomplish when shuffling pieces of cardboard, and is actually a different standard from what's enforced in tournament play (requirement there is that after shuffle, no player is able to know locations, relative orders or patterns within the deck, not that the deck is "random").

At any given time there are thousands of players online, and every deck gets shuffled at least once per game. With those numbers... unlikely results happen. They happen a lot. And they get players really, really angry, to the point that most forums have "complain about the shuffler" permathreads, because those results tend to absolutely screw you over when they happen.

[MartinCron]

I worked on a strategy game (think Risk) with an element of randomness (dice rolls) and our hardcore players were very very keen on the true quality of our randomness. I wound up persisting the context and result of every single roll cast so people could see summaries per-game, per-turn, per-user.

[hobin]

Pah. You clearly don't have much experience with roguelikes. ;)

[Natsu]

I don't know. At this point, I kind of expect an orc with a wand of death on level 1.

DYWYPI?

[jere]

>Users don't want a random playlist.

Really? Because I couldn't stand it if, after listening to my playlist several times, I could predict the exact order of the songs. That would be extremely boring, personally. In fact, that's the exact complaint of the user who asked the question:

>This frustrates me to no end because I like to listen to my music randomly, but I have a few favourite songs that I always start out with.

[baddox]

Would you ever want the same song to play twice in a row? How about 10 times in a row?

[jere]

Preferably, no. But even if that was a problem, it would only be an occasional one. The predictable playlist would get on my nerves all the time.

I suppose you'll then lecture me on how a random playlist has such undesirable properties.

But I would have to disagree. Writing a psuedo-random shuffle mode that doesn't play songs twice in a row (or even one that doesn't repeat a single song in your playlist) is trivial.

[jrockway]

The probability of that happening decreases so quickly that it's not a realistic concern.

Incidentally, today I had some song stuck in my head so I just listened to it on repeat for a while.

[JonnieCache]

Exactly. People want their expectations and their pattern matching processes to be confounded, and randomness, counterintuitively, will not do that.

[ajross]

I think that's right, but stated wrong. :) Randomness does confound our expectations. But what it does not do is confound them consistently. It's routine for a random order to play the same song twice in near succession ("I just heard this yesterday, and I have 2000 songs in this thing!"), etc...

But none of that really gets to the linked article, which is that iTunes was using a fixed shuffle order.

[ChillyWater]

You see the same thing when laying tile. If you have a small field tile with fancy glass accents or whatever, the customer really wants random uniformity, not pure random.

[arnarbi]

That was not his point. He just didn't know shuffling only happens when you activate shuffle mode, so he was getting exactly the same order (not just a "good" distribution of artists and albums).

[Dylan16807]

But once those users get through the entire song list they want the order to change. iTunes is just as wrong as picking each individual song at random but in a different way.