Game of Life 32b

This writeup is still in the works! Come back later to get information on all the mean tricks ;) Meanwhile you can download and comment the intro.

Original version : 65 bytes

We'll start with the old 65 bytes version and bring it down to 32 bytes.

</br> It will help to understand what the core algorithm does, before optimizing it. I will not go into the details of random number generation and key handling since these parts are removed in the final version anyway. The core routine computes the [https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life#Rules "normal" game of life rules, but with a twist. Instead of regarding only neighbour cells inside a 3x3 neighbourhood , ALL cells are taken into consideration, and the rules are reinterpreted as:

• If the number of cells is 3, the center cell will be alive.
• If the number of cells is 4, the center cell keeps its state.
• Otherwise, the cell dies (or stays dead).

; http://read.pudn.com/downloads208/sourcecode/asm/981812/LIFE65.ASM__.htm
; Life simulator, 72 bytes  - Vladislav Kaipetsky and Tenie Remmel 
;                 65 bytes  - Mark Andreas 
 
; If no args, regs on startup are: 
 
; AX = BX = 0000h 
; SI = IP = 0100h 
; DI = SP = FFFEh 
 
IDEAL 
MODEL TINY 
P386 
CODESEG 
ORG 100h 
 
Start:  int     1ah             ; ah=00: cx=hours, dx=tic counter 
 
        mov     al,13h          ; Set mode 13h 
        int     10h 
 
        xchg    dx,ax 
 
        push    09000h          ; DS = last 64K segment 
        pop     ds 
        push    0A000h          ; ES = video memory 
        pop     es 
                                ; BX is already zero 
RandLoop: 
        rol     ax,1            ; Generate random number 
        adc     [bx],al 
        dec     bx 
        jnz     RandLoop 
 
; BX will not be equal to 3 the first time this loop is executed, but 
; it will be for all other times.   As SI = 0100h and DI = FFFEh on 
; startup, SI - DI will be equal to 258. 
 
LifeLoop: 
        xchg    cx,ax 
AccLoop: 
        add     cl,[di+bx-64]   ; Add in this column 
        add     cl,[si+bx-2] 
        add     cl,[si+bx+318] 
        dec     bx              ; Loop back 
        jnz     AccLoop 
 
        mov     al,[si]         ; Get center cell, set pixel 
        stosb 
        stc                     ; 3 = birth, 4 = stay (tricky): 
        rcr     al,cl           ; 1.00?0000x --> 0.0x100?00 (rcr 3) 
        and     al,20h          ; ^carry   |         ^ 
                                ;          +---> 0.00x100?0 (rcr 4) 
        or      [si-1],al       ; Add in new cell     ^ 
        shr     [byte di-65],5  ; Shift previous value 
 
        mov     bl,3            ; 3 iterations in AccLoop 
        inc     si              ; Loop while not zero 
        jnz     LifeLoop 
 
        mov     ah,1            ; Check for key 
        int     16h 
        jz      LifeLoop        ; Loop if no key 
 
        xchg    ax,bx           ; Set text mode 
        int     10h 
        ret                     ; Return 
End     Start

Remove key handler and RNG : 44 bytes

Start:  
 
        mov     al,93h          ; Set mode 13h 
        int     10h 
 
        push    09000h          ; DS = last 64K segment 
        pop     ds 
        push    0A000h          ; ES = video memory 
        pop     es 
                                ; BX is already zero  
LifeLoop: 
        xchg    cx,ax 
AccLoop: 
        add     cl,[di+bx-64]   ; Add in this column 
        add     cl,[si+bx-2] 
        add     cl,[si+bx+318] 
        dec     bx              ; Loop back 
        jnz     AccLoop 
 
        ;mov     al,[si]         ; Get center cell, set pixel 
		lodsb
        stosb 
        stc                     ; 3 = birth, 4 = stay (tricky): 
        rcr     al,cl           ; 1.00?0000x --> 0.0x100?00 (rcr 3) 
        and     al,20h          ; ^carry   |         ^ 
                                ;          +---> 0.00x100?0 (rcr 4) 
        or      [si-1],al       ; Add in new cell     ^ 
        shr     [byte di-65],5  ; Shift previous value 
 
        mov     bl,3            ; 3 iterations in AccLoop 
        ; inc     si              ; Loop while not zero 
        jmp short     LifeLoop

Switching to Textmode : 39 bytes

		 push 0xb800
		 pop ds
LifeLoop:
         stc                   ; 3 = birth, 4 = stay (tricky):
         rcr al,cl             ; 1.00?0000x --> 0.0x100?00 (rcr 3)
         and al,20h            ; ^carry   |         ^
         or [si-2],al          ; Add in new cell     ^
         shr byte [si-160-6],5    ; Shift previous value
         mov bl,6 
		xchg cx,ax
AccLoop: add  cl,[si+bx-160-4]    ; Add in this column
         add  cl,[si+bx-4]
         add  cl,[si+bx+160-4]
         dec  bx               ; Loop back
         dec  bx               ; Loop back
         jnz  AccLoop
		 lodsw
         jmp LifeLoop