Re: A86: Efficiency Problem

To: assembly-86@lists.ticalc.org
Subject: Re: A86: Efficiency Problem
From: Jimmy =?iso-8859-1?Q?M=E5rdell?= <yarin@acc.umu.se>
Date: Fri, 11 Dec 1998 03:15:14 +0100
Delivered-To: assembly-86-outgoing@towerguard.unix.edu.sollentuna.se
In-Reply-To: <fcf3c87b.36707500@aol.com>
Reply-To: assembly-86@lists.ticalc.org

At 20:27 1998-12-10 -0500, you wrote:
>
>The following is a fragment(?) of code from a game I'm working on called Nerd
>Quest I. It's the a part that displays the current weapon on the status
>screen. It seems to me that this code is incredibly ineffiecient, and there's
>gotta be a faster way of doing this. 

Hehe... your source code is probably _the_ classic example of beginners
mistakes :-)

Instead of all the checks, you use a lookuptable:

 ld a,(Weapon) ;Weapon EQU $F602
 add a,a
 ld hl,lookuptable
 ld d,0
 ld e,a
 add hl,de
 call _ldhlind  ; $4010 (or LD_HL_MHL) 
 ; And we're done! 14+2*16 = 46 bytes
 call_puts
 jp somewhere

lookuptable:
 .dw W1,W2,W3,W4,W5,W6,W7,W8,W9,W10
 .dw W11,W12,W13,W14,W15,W16

...or the smaller, slightly slower, version...

 ld hl,DataSection
 ld a,(Weapon)
 or a
 jr z,Done
 ld b,a
 xor a
SkipStrings:
 ld c,$FF ; Make sure the loop doesn't terminate because of the counter
 cpir     ; Search string for nullterminating zero (that is - end of string)
 inc hl   ; HL -> next string
 djnz SkipStrings
Done: 
 ; Done! 18 bytes
 call _puts
 jp somewhere

--
Real name:     Jimmy Mårdell         
Email:         mailto:yarin@acc.umu.se
Homepage:      http://www.acc.umu.se/~yarin/

Icarus Productions homepage: http://icarus.ganymed.org/

References:

A86: Efficiency Problem

From: ZeromusMog@aol.com