Pseudo-random numbers/PCG32: Difference between revisions

=={{header|FreeBASIC}}==

<syntaxhighlight lang="vbnet">#define floor(x) ((x*2.0-0.5) Shr 1)

Const As Ulongint mask64 = &HFFFFFFFFFFFFFFFF

Const As Ulongint mask32 = &HFFFFFFFF

Const As Ulongint cte = 6364136223846793005

Dim Shared As Ulongint state, inc

Function next_int() As Ulongint

' return random 32 bit unsigned int

Dim As Ulongint old = state

state = ((old * cte) + inc) And mask64

Dim As Ulongint xorshifted = (((old Shr 18) Xor old) Shr 27) And mask32

Dim As Ulongint rot = (old Shr 59) And mask32

Dim As Ulongint answer = (xorshifted Shr rot) Or (xorshifted Shl ((-rot) And 31))

answer And= mask32

Return answer

End Function

Function next_float() As Double

' return random float between 0 and 1

Return next_int() / (2 ^ 32)

End Function

Sub seed(seed_state As Ulongint, seed_sequence As Ulongint)

state = 0

inc = ((seed_sequence Shl 1) Or 1) And mask64

next_int()

state = (state + seed_state) And mask64

next_int()

End Sub

Dim As Integer i, hist(4)

seed(42, 54)

For i = 1 To 5

Print next_int()

Next i

Print !"\nThe counts for 100,000 repetitions are:"

seed(987654321, 1)

For i = 1 To 100000

hist(floor(next_float() * 5)) += 1

Next i

For i = 0 To 4

Print Using "hist(#) = #####"; i; hist(i)

Next i

Sleep</syntaxhighlight>

{{out}}

<pre>2707161783

2068313097

3122475824

2211639955

3215226955

The counts for 100,000 repetitions are:

hist(0) = 20049

hist(1) = 20022

hist(2) = 20115

hist(3) = 19809

hist(4) = 20005</pre>