Useful Routines - Cemetech | Forum | z80 Assembly [Topic]

Home Archives Projects Forum Tools About

Login [Register]

Don't have an account? Register now to chat, post, use our tools, and much more.

Latest Headlines

» Planned Server Maintenance, May 27th-28th.
» HP Prime Datasheet and Screenshots
» Cemetech Member Carves Intricate Wooden TI-83+
» HP Prime Multitouch Graphing Calculator: The Scoop

Online Users

There are 92 users online: 3 members, 65 guests and 24 bots.
Members: luoxue.
Bots: VoilaBot (1), MSN/Bing (1), Magpie Crawler (3), Googlebot (18), MSN/Bing (1).

RSS & Social Media

Follow @cemetech

'Like' Cemetech

News Headlines

Latest Posts

SAX

You must log in to view the SAX chat widget

Useful Routines

» Forum > z80 Assembly
	» Goto page Previous 1, 2, 3, 4, 5, 6 » View previous topic :: View next topic

Author Message

Xeda112358

Power User

Joined: 09 Nov 2010
Posts: 354

Posted: 03 Jul 2012 11:10:04 am Post subject:

Here is another routine that I made yesterday for a pseudo-random number generator: Code: PseudoRandWord: ;Outputs: ; BC was the previous pseudorandom number ; HL is the pseudorandom number ;f(n+1)=(241f(n)+257) mod 65536 ;65536 ;181 cycles, add 17 if called ld hl,(randSeed) ld c,l ld b,h add hl,hl add hl,bc add hl,hl add hl,bc add hl,hl add hl,bc add hl,hl add hl,hl add hl,hl add hl,hl add hl,bc inc h inc hl ld (randSeed),hl ret There are a few other nice features, too. For example, every 16-bit value is hit if you run this 65536 times. Or, if you only read 1 byte (for example, H from the output), it will hit every 8-bit number once if you run this 256 times. Plus, it can be seeded

Back to top

Xeda112358

Power User

Joined: 09 Nov 2010
Posts: 354

Posted: 07 Mar 2013 05:28:50 pm Post subject:

I was optimising some algorithms and code in Grammer and I came across a pretty big speed optimisation for computing 16-bit GCD: Code: GCDDE_HL: ;Inputs: ; HL,DE are the two values ;Outputs: ; B is 0 ; DE is 0 ; HL is the GCD ; C is not changed ; A is not changed ld b,1 or a CheckMax: ; sbc hl,de ;ED52 15n jr z,AdjustGCD ;28 12n-5 jr nc,ParityCheck ;30 12n-5 add hl,de or a ex de,hl ParityCheck: ; bit 0,e ;CB 8a jr nz,DE_Odd ;20 12a-5b bit 0,l ;CB 8b jr z,BothEven ;28 12b-5c rr d ;CB 8(n-a-b-c) rr e ;CB 8(n-a-b-c) jp CheckMax ;C3**** 10(n-a-b-c) BothEven: ; inc b ;04 4c rr d \ rr e ; 16c HL_Even: rr h \ rr l ; 16c jp CheckMax ; 10c DE_Odd: ; bit 0,l ; 8b jr z,HL_Even ; 12b-5d sbc hl,de ; 15d rr h \ rr l ; 16d jp nz,CheckMax ; 10d AdjustGCD: ; ex de,hl ; 4 dec b ; 4 ret z ; 11+4(k>0) add hl,hl ; 11k djnz $-1 ; 13k-5 ret ; -- I was using a slightly more naive approach before, computing the mod of two 16-bit values over and over (the Euclidean Algorithm). This code is pretty hefty, though, at 61 bytes. You can save three bytes by turning the JP instructions into JR, but there will be a tiny speed loss of a few cycles

Back to top

Display posts from previous:

Register to Join the Conversation

Have your own thoughts to add to this or any other topic? Want to ask a question, offer a suggestion, share your own programs and projects, upload a file to the file archives, get help with calculator and computer programming, or simply chat with like-minded coders and tech and calculator enthusiasts via the site-wide AJAX SAX widget? Registration for a free Cemetech account only takes a minute.

» Go to Registration page

Useful Routines

	» Goto page Previous 1, 2, 3, 4, 5, 6 » View previous topic :: View next topic
Page 6 of 6	» All times are GMT - 5 Hours

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

[Switch to Mobile view]