Random number generation, without built-in random number generation libraries [duplicate]

Question

Task:

Make a random number generator. The catch is that you can't use any built-in randomness functions. Your random numbers must be anything between 0 and 100, though they do not have to be floating point.

Rules:

• It must produce a pseudorandom number.
• Randomness defined: If you run it x times, then x times again, the two sequences will be unlikely to be identical. Where 2 < x < 10.
• It is not required that your random number generator passes any specific test about the quality of the generated numbers, as long as the previous rule is respected.
• Any language is accepted, except Golfscript, see here.
• This is code-golf, so the shortest answer in bytes wins.
• You may not hard-code the output numbers or read them from a file.
• Post 5 numbers generated by your program.
• Good luck!

Answer 1

C (46)

The stack pointer is sort of a random number

main(x){printf("%d",((unsigned char)&x)%100);}

Numbers I got:

20
40
4
52
36

Answer 2

python, 49

x=7
def r(x):print(x%100);return(69069*x+1)%2**32

This is my first time golfing, I think this is within the rules but I'm not sure. This is a simple linear congruential generator, with starting x value as seed. User time is not used. To use, type x=r(x).

Here are the results:

7
84
25
62
47

Answer 3

Linux utils and ALSA, 41

Not a winner, but possibly a more accurate source of random noise than the current time:

arecord -qfS32|od -l -j48 -N8|cut -c27-28

Sample 5 random numbers:

32 53 81 83 26

Answer 4

Java - 250 249 characters

import java.awt.*;class A{public static void main(String[]y)throws Exception{int z=200,u=z*z-1,n=7;java.awt.image.BufferedImage b=new Robot().createScreenCapture(new Rectangle(z,z));while(u>0)n^=b.getRGB(u/z,u--%z);System.out.println((n>>>1)%101);}}

It uses the topright 200x200 pixels of the screen as a source of randomness. The result is an integer between 0 and 100.

I runned it 5 times (this last version) and got this:

97
84
38
40
65

I had to move my windows around between each run.

Needless to say, it is a very poor random-generator:

• It is frequently predictable.
• It is easily stalled to keep giving always the same output.
• It is unlikely to produce each number between 0 and 100 with an equal probability.

So, this should not be used by any serious purpose.

Answer 5

Java - 206 characters

class V{public static void main(String[]y)throws Exception{java.io.InputStream o=new java.net.URL("http://bit.ly/1gxstDI").openStream();int x,n=7;while((x=o.read())>0)n^=x;System.out.println((n>>>1)%101);}}

Similar to my previous answer. However, it is smaller and has some better randomness properties (but still bad). It fetches random data from http://en.wikipedia.org/wiki/Special:random as a seed (I am borrowing this idea from this answer).

Running it five times, here is the output:

25
15
93
32
9

Answer 6

bash, 17

date +%N|tail -c3

Outputs the last two digits of a nanosecond timestamp.

Sample output

$ ./random
24
$ ./random
52
$ ./random
82
$ ./random
69
$ ./random
72

Answer 7

APL, 9 chars

101|+/⎕TS

Nothing new. It sums the components of the TimeStamp vector (current year, month… down to ms) and takes the remainder mod 101.

Answer 8

Python 2.7 - 82 bytes

import timeit
print timeit.Timer('for i in range(1000):i**i').timeit(1)*10000%100

This can definitely be golfed down more. I couldn't get timeit working when using from timeit import* but I think I only lost one character there. This is my first time using the module so I'm probably missing a lot of stuff that could save characters.

Times how long it takes in (seconds?) to calculate i**i for 0-999, multiplies that by 10000 and takes the modulus of 100 to get the result in the correct range.

Since this works off of hardware deviation rather than a pseudorandom formula like most programs do, you could even call this "more random" than random.random()*100. :)

(That last part probably isn't true, but until someone explains why I'll continue to believe it.)

Answer 9

Perl, 17

Seems like predictability isn't so much of an issue here, so here's a simple one:

print time**3%101

Five outputs:

59
38
17
14
94

I hope this answer highlights the importance of objectively defining the question.

Answer 10

PowerShell (66)

[Convert]::ToInt32((""+([guid]::newguid())).SubString(0,2),16)%100

5 outputs:

10
92
13
84
0

Answer 11

Ruby, 69

def r()(Time.now.to_f.to_s+$$.to_s+$-I.join).bytes.reduce(:+)%100;end

Online Version for testing. Uses the current time in ms, the process id ($$) and the runtime environment ($-I) for creating a pseudo-random number.

Output:

47
44
39
43
88

Answer 12

Java, 99 chars

class b{public static void main(String[]a){System.out.println(System.nanoTime()/a.hashCode()%99);}}

75
28
34
88
16

If you want to be really really cheap:

java 88 Chars

class b{public static void main(String[]a){System.out.println(System.nanoTime()/9%99);}}

99
86
61
15
19

Answer 13

Smalltalk, 39

not a production quality random generator:

OperatingSystem getMicrosecondTime\\101

but as I generated those 5 values by eval'ing them interactively, it's me who makes it random.

Output of 5 evaluations:

 93 28 25 6 25 

PS: the free running us timer is normally used for profiling...

A much better random gen would be:

'/dev/random' asFilename readStream nextByte/2.55

Answer 14

bash — 108 106 bytes

ls -al|tee -a X|grep -o [0-9]|xargs -n3|sed 's/ //g'|sort -u|awk 'BEGIN{X=0}{X=xor(X,$0)}END{print X%101}'

Gets a set of all three-digit triplets from a detailed listing, exclusive ORs them with each other, then prints a result modulus 101 to get [0, 100].

Depending on the activity in the directory, may be random-ish, or dynamic but predictable, but should never be static. Running it 1000 times, I was surprised that there didn't seem to be any patterns.

Sample output:

$ ls -al|tee -a X|grep -o [0-9]|xargs -n3|sed 's/ //g'|sort -u|awk 'BEGIN{X=0}{X=xor(X,$0)}END{print X%101}'
37
$ ls -al|tee -a X|grep -o [0-9]|xargs -n3|sed 's/ //g'|sort -u|awk 'BEGIN{X=0}{X=xor(X,$0)}END{print X%101}'
95
$ ls -al|tee -a X|grep -o [0-9]|xargs -n3|sed 's/ //g'|sort -u|awk 'BEGIN{X=0}{X=xor(X,$0)}END{print X%101}'
62
$ ls -al|tee -a X|grep -o [0-9]|xargs -n3|sed 's/ //g'|sort -u|awk 'BEGIN{X=0}{X=xor(X,$0)}END{print X%101}'
6
$ ls -al|tee -a X|grep -o [0-9]|xargs -n3|sed 's/ //g'|sort -u|awk 'BEGIN{X=0}{X=xor(X,$0)}END{print X%101}'
51

Answer 15

CMD / Batch - 14 Bytes

echo %time:~9%

Grabs milliseconds off the end of the variable %time%.

Add @ before the command to make it only output the number.

C:\>echo %time:~9%
40

C:\>echo %time:~9%
53

C:\>echo %time:~9%
19

C:\>echo %time:~9%
73

C:\>echo %time:~9%
25