Shortest code to produce non-deterministic output

Question

You need to produce output that is non-deterministic.

In this case, this will be defined to mean that the output will not always be the same result.

Rules:

• A pseudo-random number generator that always has the same seed does not count.

• You can rely on the program being run at a different (unknown) time each execution.

• Your code's process id (if it's not fixed by the interpreter) can be assumed to be non-deterministic.

• You may rely on web-based randomness.

• Your code may not take non-empty input. Related meta post.

• The program is not required to halt, but the output must be displayed.

Leaderboard

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Answer 1

><>, 4 3 bytes

(crossed out 4 still looks like 4)

0nx

Try It Online!

Outputs some amount of 0's.

On an empty stack n throws an error and terminates the program. x chooses a random direction for the stack pointer. This means that for each 0 printed, there is a 50% chance for the program to exit.

Answer 2

Mathematica, 6 bytes

Date[]

Pretty self-explanatory. (This function was superseded by DateList[] in later versions, but Date[] still runs.)

For 8 bytes one can also use Random[] (itself a legacy function).

Answer 3

MATL, 1 byte

r

Uniform random number generator between 0 and 1. The seed is randomly set for each execution of the program. Try it online!

Answer 4

C89 with GCC/Clang, 20 bytes

The other C solution just segfaults every time when built with GCC or Clang. This, though.

main(n){puts(&n+1);}

Which looks like:

$ for _ in `seq 1 50`; do ./test_89; done
���z�U
�VW��U
�F��U
�v�f2V
��FV
���*=V
�6���U
�20wU
��
�+V
�6
   �U
��V�uU
�v��V
���K�U
��7�qU
�6S�jU
�&�WU
��wV
��6l�U
���U
�F�ߨU
�f���U
���s7V
�f��?V
��;B�U
�;��U
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�vKV
�V?]wU
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�6X�U
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�69��U
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�vx4.V
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�F��U
�֤BQV
��#�U
���1^U
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��AݗU

Quite a lot of unprintable junk but it's nondeterministic!

Answer 5

PHP, 12 bytes

<?=uniqid();

Outputs a unique ID 583f4da627ee3 based on the current time in microseconds. ↑

Answer 6

Knight, 2 bytes

`R

Try it online!

`   Run as a shell command:
R   A random integer

The non-deterministic output is to stderr. The C interpreter implicitly converts the number to string and tries to run it as a shell command. With very high chance (if not 100%), such a command or executable does not exist in PATH, and an error message that looks like sh: <some random number>: command not found is printed to stderr.

This is shorter than the straightforward O R which prints the random number to stdout.

Answer 7

Borland C on Windows, 12 bytes

m(){puts();}

I rewrote it because they said it's possible to use one function. The compiler doesn't check the argument so it compiles it; but puts sees an unknown address and begins to print what that address points to until it finds the byte 0x00. It would not work if that address was out of memory, but here it prints something.

Answer 8

Japt, 1 byte

Ð

Test it online!

How it works

When Japt is compiled to JavaScript, it replaces Ð with new Date(. The close-paren is automatically added by the interpreter, and the result of the last expression is automatically printed, so this prints the current date/time.

An alternate solution would be Mr, which uses Math.random. Japt also has the variable K set to Date (no clue why I did that, it's almost entirely useless), which I guess makes K a valid function entry.

Answer 9

Jelly, 2 bytes

9X

Idk if this works. I've never done anything in jelly before, and I'm on my phone right now.

Int from 0 to 9.

Answer 10

C#, 36 22 bytes

a=()=>a.GetHashCode();

Yay.

Answer 11

Java2K, 9 bytes

I don't recommend trying to write an approximation of a deterministic program in this language.

11 6/*/_\

This function has a 90% chance to return 1, otherwise it will return a random number. 11 6 is the name of the division function. A function is called like <name>/<arg0>/<arg1>\. Basicaly every function returns the "correct" result 90% of the time, or else a random number.

The token * is replaced by a random number, say 203. The _ token is replaced by the previous argument, i.e. 203. So, this function will divide 203 by 203 which has (see below) a 90% chance of returning 1.

Answer 12

C++, 26 19 Bytes

std::cout<<new int;

Returns a different memory address each time it's run

Answer 13

Minecraft, 2 bytes

/r

Must be written into chat when playing on multiplayer servers. Will throw an error if you hadn't messaged (/tell) anybody recently. Otherwise, shows both players a random message.

Note: I'm not really sure if this is a legit solution :)

Minecraft, 4 bytes (+2 blocks)

help

Ties with another Minecraft answer from @Pavel

This is based on Minecraft's Easter egg:

When you type help or /help in a Command block, a random message starting with "Searge says:" is displayed, for example "Searge says: Ask for help on twitter". Here is a full list of messages.

Answer 14

C, 5 bytes

main;

Try it online!

Answer 15

Julia, 4 bytes

rand

Try it online!

time

Try it online!

Answer 16

x86/amd64 machine language (Pentium or higher), 3 bytes

0:       0f 31                   rdtsc  
2:       c3                      retq

This uses the RDTSC instruction that may not be available on older processors. To test, try the following C program on Linux x86/amd64

#include <stdio.h>
int main(){
  for( int i = 0; i < 10; i++ ) {
    printf( "%d\n", ((int(*)())"\x0f\x31\xc3")() );
  }
}

Or try it on Ideone.

Answer 17

Cubix, 3 bytes (non-competing)

@OD

Outputs a random positive number of zeroes. Non-competing because I added D just a few minutes ago. Before it was added, there was absolutely no way to randomize anything in Cubix.

Test it online!

How it works

Before the code is run, it's padded with no-ops . and formed into a cube net. Here's what the net for this particular program looks like:

  @
O D . .
  .

Now the code is run, starting on the left-most face and heading to the right.

First, O outputs the top item on the stack as a number. At the beginning of the program, the stack is an infinite fount of zeroes, so this prints 0.

Next, D sends the IP (instruction pointer) in a random direction: possibly up to the @ which ends the program, and possibly back to the O which prints another 0. This continues until whenever the IP hits the @.

@DO and OD@ also work, each printing zero or more zeroes.

Answer 18

PHP, 10 Byte

<?=time();

This prints the current Unix time which – of course – isn't random but changes when you call the program several times. The output I just got is 1480548602.

Answer 19

APL, 2 bytes

?9

This uses APL's roll (?) operator. The program prints a pseudo-random number between 1 and 9.

Answer 20

PHP 10 bytes

<?=rand();

Prints a random number between 0 and getrandmax(). Which may vary based on what computer it's run on.

Answer 21

Lua, 9 bytes

print({})

Outputs the internal address of the Lua table object:

table: 0x2370ab0

If you're running from the interactive interpreter, you can use just 3 bytes:

> ={}
table: 0x23719c0

Answer 22

C, 19

f(a,b){putchar(b);}

In C the second declared variable in a function's arguments is random based on memory. Assuming the arguments were not actually declared, i.e. you just called f();.

So this function can be simply called with no input-arguments. That is, just: f(); and the output will be a random character.

Try it online! (Note: output might be an unprintable character, run the program a few times to see variation, you should get more printable characters than non-printable characters)

Answer 23

C (gcc), 18 bytes

f(){printf("%d");}

This one may be difficult to test since TIO will give you a cache hit. Just add some whitespace and try it again.

Try it online!

Answer 24

Retina, 3 bytes

?&`

Try it online!

Yay, Retina can finally compete in challenges that require randomness! \o/

Explanation

?& is a compound stage which executes its child stage with a 50% probability. That child stage is itself a Count stage, which counts the number of empty matches in the empty input (1). So if the child stage is run, the result is 1, if it isn't, then the empty input remains unchanged and we get an empty string.

A fun alternative for the same byte count would be:

?+`

Try it online!

This one uses a random loop (which uses a coin toss before each iteration to decide whether to continue). This one has a 50% chance of printing an empty string, 25% of printing 1 (one iteration) and a 25% chance of printing 2 (two or more iterations).

Answer 25

Kotlin script (.kts), 12 bytes

print(Any())

Any is a compile-time time wrapper for Object, default toString() of any object is class name@hashcode. Probably the shortest solution that runs on the JVM.

If .kts is cheating:

18 bytes: fun a()="${Any()}" (forgot functions are a valid answer)

38 bytes: fun main(a:Array<String>)=print(Any())

Answer 26

Wumpus, 4 bytes

UFO@

Try it online!

Outputs a uniformly random choice of 2, 5 or 8.

Explanation

Apart from a regular stack, Wumpus also has 20 registers which are arranged around the faces of an icosahedron. You can imagine the icosahedron as a d20 resting on a table: the face touching the table is the "active" face (i.e. the register that can currently be interacted with). Also, every face has an index from 1 to 20. Initially, the active face is 1 and the three adjacent faces are 2, 5 and 8 (see the README in the Wumpus repo for the full net).

U   Randomly tip the icosahedron onto one of the three adjacent faces, i.e.
    change the active faces to either 2, 5 or 8.
F   Push the index of the currently active face.
O   Output as a decimal integer.
@   Terminate the program.

Alternatively:

DFO@

This one completely randomises the orientation of the icosahedron, so it prints a random number from 1 to 20, inclusive.

Answer 27

Lost, 7 bytes

@%"
///

Try it online!

Since Lost starts the pointer in a random place facing a random direction, it's refreshing not making the output deterministic for once. I think this is the optimal solution since you need the @ and % in order to end the program, the " to push stuff to the stack at random, and the /// to avoid infinite loops.

Answer 28

Intercept 1.1, 37 bytes

Prints newlines to the terminal. You'll probably have to leave this one overnight, as there is a delay of 5-15 minutes (it's random!) between each newline. Note that while you can determine what is being printed, you can't determine how often it's being printed.

Input is marked with a >>. The command prompt is the empty >>.

Assuming a system with only TZ_INFECT installed...

>> malware bm bitminer
creating bm (bitminer)
... wait a minute ...

finished creating bm (bitminer)
>> software install 1
Success
bm installed

...wait...
(newlines)








>>

Note that I'm using a custom client that prefixes [BROADCAST] to all broadcast events.

How???

TZ_INFECT is Intercept's malware generator. We can generate a bitminer by running malware <name> bitminer. This will create a new piece of software with the given name of type bitminer

We then install the bitminer: software install <index>, where index is the 0-based index of the software as given by software list. This is why I made sure the only piece of software on the system was the malware generator. This places our new bitminer at index 1.

There is a bug in the implementation of bitminer that results in an empty broadcast event to be sent to the client whenever bits are generated. Since bits are generated at random intervals, the broadcasts are sent at random intervals. Voilia, non-deterministic output!

Note: the newlines are harder to detect using the official game client, but you can see them by running a command and watching the newlines slowly push the resulting output off the screen.

Screenshots coming in a few hours while I wait for the output.
After 20 minutes (the [BROADCAST] is a newline):

After 2 days:

Answer 29

Taxi, 222 220 218 bytes

Go to Heisenberg's:w 1 r, 3 r, 1 l.Pickup a passenger going to The Babelfishery.Go to The Babelfishery:s 1 r, 1 l.Pickup a passenger going to Post Office.Go to Post Office:n, 1 l, 1 r.Go to Taxi Garage:n 1 r, 1 l, 1 r.

Prints a random number. The spec does not give any details on what number should be. The last statement can be omitted (producing 184 bytes) if you don't mind the code giving an error after printing the output.

Try it online!

Answer 30

PARI/GP, 2 bytes

\s

Attempt This Online!

\s prints the state of the PARI stack and heap, which is non-deterministic.

Example output:

 Top : 7fadf82bd000   Bottom : 7fadf7b1be00   Current stack : 7fadf82bcfb8
 Used :                         9  long words  (0 K)
 Available :                    999991  long words  (7808 K)
 Occupation of the PARI stack :   0.00 percent
 1 objects on heap occupy 9 long words

 10 variable names used (10 user + 0 private) out of 65535