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6419 hidnplayr 1 
; ----------------------------- MOTHER.ASM -----------------------------
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; Mother-of-All random number generator by Agner Fog 1998
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; 32-bit mode version for 80x86 and compatible microprocessors
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;
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; MRandom returns a floating point number between 0 and 1.
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; MRandomInit must be called before the first call to MRandom.
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;
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; C++ prototypes:
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; extern "C" void MRandomInit (int seed);
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; extern "C" double MRandom (void);
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; extern "C" int MIRandom (int min, int max);
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;
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; © 1998, 2004 Agner Fog.
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; GNU General Public License www.gnu.org/copyleft/gpl.html
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; ----------------------------------------------------------------------
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; The MRandom function is optimized for the Pentium microprocessor.
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iglobal
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        mf3     dd 2111111111           ; factors
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        mf2     dd 1492
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        mf1     dd 1776
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        mf0     dd 5115
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endg
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uglobal
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        m0      dd ?                    ; history buffer
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        m1      dd ?
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        m2      dd ?
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        m3      dd ?
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        mc      dd ?
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        temprng dq ?                    ; used for conversion to float
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endg
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proc init_random
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        xor     ecx, ecx
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        ; make random numbers and put them into buffer
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  @@:
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        imul    eax, 29943829
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        dec     eax
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        mov     [m0+ecx*4], eax
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        inc     ecx
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        cmp     ecx, 5
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        jb      @r
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        push    edi
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        mov     edi, 19
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  @@:
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        call    MRandom
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        fstp    st0
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        dec     edi
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        jnz     @r
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        pop     edi
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        ret
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endp
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proc MRandom
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        call    MBRandom                ; random bits
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        mov     edx, eax                ; fast conversion to float
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        shr     eax, 12
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        or      eax, 3ff00000h
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        shl     edx, 20
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        mov     dword[temprng+4], eax
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        mov     dword[temprng], edx
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        fld1
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        fld     [temprng]               ; partial memory stall here
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        fsubr   st0, st1
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        ret
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endp
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proc MIRandom, max, min                 ; make random integer in desired interval
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        call    MBRandom                ; make random number
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        mov     edx, [max]
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        mov     ecx, [min]
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        sub     edx, ecx
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        js      .error                  ; max < min
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        inc     edx                     ; max - min + 1
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        mul     edx                     ; multiply random number by interval and truncate
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        lea     eax, [edx+ecx]          ; add min
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        ret
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  .error:
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        mov     eax, 80000000h          ; error exit
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        ret
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endp
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proc MBRandom
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        push    edi
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        mov     eax, [mf3]
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        mul     [m3]                    ; x[n-4]
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        mov     ecx, eax
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        mov     eax, [m2]               ; x[n-3]
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        mov     edi, edx
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        mov     [m3], eax
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        mul     [mf2]
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        add     ecx, eax
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        mov     eax, [m1]               ; x[n-2]
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        adc     edi, edx
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        mov     [m2], eax
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        mul     [mf1]
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        add     ecx, eax
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        mov     eax, [m0]               ; x[n-1]
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        adc     edi, edx
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        mov     [m1], eax
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        mul     [mf0]
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        add     eax, ecx
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        adc     edx, edi
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        add     eax, [mc]
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        adc     edx, 0
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        mov     [m0], eax
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        mov     [mc], edx
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        pop     edi
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        ret
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endp