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Random Functions

Posted by: britlion - 2012-06-19, 12:07 AM - Forum: How-To & Tutorials - Replies (6)

Boriel has included a better random function in the code; but this passes through floating point numbers, which is potentially fairly slow - and for games we usually require integer numbers anyway!

I've written a few functions that are a possible alternative.

This is the base function that does the hard work of generating a random number from 0-255 in the A register (or as a return value, conveniently enough). This is the same random number generator that Boriel is using, incidentally. (Based pretty much wholly on Patrik Rak's stream random generator).

Code:
FUNCTION FASTCALL randomBase () as uByte
ASM
random: ld  hl,$A280       ; xz -> yw
        ld  de,$C0DE       ; yw -> zt
        ld  (random+1),de   ; x = y, z = w
        ld  a,e             ; w = w ^ ( w << 3 )
        add a,a
        add a,a
        add a,a
        xor e
        ld  e,a
        ld  a,h             ; t = x ^ (x << 1)
        add a,a
        xor h
        ld  d,a
        rra                 ; t = t ^ (t >> 1) ^ w
        xor d
        xor e
        ld  h,l             ; y = z
        ld  l,a             ; w = t
        ld  (random+4),hl
        ;ret (Not necessary, since the compiler will add ret to the end)
END ASM
END FUNCTION

This function will update the seed value based on the current frames counter. To improve randomness, get the user to have a human interaction that can take a variable amount of time and then run this.

Code:
SUB FASTCALL updateSeed()
REM Updates the random generator seed from the FRAMES system variable.
t()
ASM
LD A,E
EX DE,HL
LD HL,random+2
XOR (HL)
AND A
JR NZ,updateSeedNotZero
INC A
updateSeedNotZero:
LD (HL),A


LD HL,random+4
LD A,E
XOR (HL)
LD (HL),A
INC HL
LD A,D
XOR (HL)
LD (HL),A

END ASM
END SUB

The above function depends on my timer function, which gets the value in FRAMES:

Code:
FUNCTION FASTCALL t() as uLong
asm
    DI
    LD DE,(23674)
    LD D,0
    LD HL,(23672)
    EI
end asm
end function

This function returns a value from zero to the specified limit number (limit <= 255)

Code:
FUNCTION fastcall randomBin(limit as uByte) as uByte
ASM

AND A
RET Z ; Input zero, output zero.
LD B,A ; Save A

LD C,255
randomBinLoop:
RLA
JR C, randomBinLoopExit
RR C
JR randomBinLoop ; loop back until we find a bit.
randomBinLoopExit:

randomBinRedoCall:
call random
AND C
CP B
RET Z
JR NC, randomBinRedoCall

END ASM
END FUNCTION

it's worth noting that the issue with this is that it basically rolls a random, and if it's bigger than limit, it rolls another one. This could potentially take a while, and isn't guaranteed to be fast. Though the probability of failing to hit the zone is kept to 50%, so on average it will roll 1.5 random numbers, I think, per call. This should usually be faster than a floating point multiply, I believe.

If you do want a number a random number between 0 and 1, using FIXED is quite a lot faster than float. This routine uses randombase to do that:

Code:
FUNCTION FASTCALL randomFixed() as FIXED
ASM
call random
push AF
call random
ld l,A
POP AF
ld h,a
ld d,0
ld e,d
END ASM
END FUNCTION

Timings:

Code:
dim time as uLong
DIM n as uInteger
DIM variable as uByte
time=t()

for n=0 to 20000
REM One line of the following three:
'variable=rnd*128
'variable=randomFixed()*128
'variable=randomBin(128)

next n

print t()-time

20,000 loops took:

variable=rnd*128 => 1180 frames.

variable=randomFixed()*128 => 613 Frames (1.92 x faster)

variable=randomBin(128) => 74 frames. (this example is 16 x faster) (worst case averages 13x faster; best case averages 22x faster)
(This does vary by limit, but is never > 89 frames for any limit chosen. Can be as low as about 52. Average is about 64.)

All three, of course, return an integer from 0 to 127 (the last 0-128; this chosen because it's a worse case scenario for timing).

For scale, 20,000 loops calling randomBase takes 37 frames. Of course, this returns a number from 0-255 regardless, with no option to set the upper bound.

Re: DEFB (*solved*)

Posted by: britlion - 2012-06-16, 04:53 PM - Forum: Bug Reports - Replies (2)

	Oh dear. DEFB 157 DEFB "Man(e;@ " DEFB 161 test.bas:1001 Error: illegal preprocessor character '@' Build Failed! So much for that idea.

DEFB

Posted by: britlion - 2012-06-16, 04:27 PM - Forum: Core - Replies (1)

	I can do DEFB 1,2,3,4 And I can do DEFB "Hello World" But I can't do DEFB "Hello World",10 And I wish I could

Inequality (*solved*)

Posted by: britlion - 2012-06-06, 10:24 PM - Forum: Bug Reports - Replies (3)

Am I doing something wrong here? I think the order of operations is messing up. This looks very odd. Is BAND a lower priority than = ?

Code:
dim n as uInteger
cls

for n=0 to 65530
    print at 10,10;n;"  ";n BAND 7
    print at 12,6;"n BAND 7 = 7 is ";
    IF n BAND 7 = 7 then 
        print "TRUE "
    else 
        print "FALSE"
    END IF
pause 0
next n

I /think/ this is doing boolean logic of

( n BAND ( 7 = 7 ) )

Or, n BAND 1

Which can't be right, surely?

HOWTO: Put BeepFX Sound into ZXB code

Posted by: britlion - 2012-06-02, 01:28 PM - Forum: How-To & Tutorials - Replies (5)

Shiru's Beepfx (http://shiru.untergrund.net/files/beepfx.zip) is quite an interesting tool for sound effects. He doesn't believe it can be used for tunes - but it can do different pitched "tones" and include pauses, and that spells tune to me. Beepola is probably a better choice for real tune making, though.

Anyway - the asm it produces is not compatible with zxb's assembler. So I did the working out of how to tweak it to work.

So the sound calling routine would look like this:

Code:
SUB sound(soundNum as uByte)
asm
#include "BeepFXPlayer.asm"
#include "SoundData.asm"

SoundEnd:
pop IX

end asm
end sub

And BeepFXPlayer would always be the same tweaks, so I present my version here:

Code:
playBasic:
play:
	ld hl,soundEffectsData	;address of sound effects data
	di
	push ix
	push iy

	ld b,0
	ld c,a
	add hl,bc
	add hl,bc
	ld a,(hl)
	inc hl
	ld h,(hl)
	ld l,a
	push hl
	pop ix			;put it into ix
    
	ld a,(23624)	;get border color from BASIC vars to keep it unchanged
	rra
	rra
	rra
	and 7
	ld (sfxRoutineToneborder+1),a
	ld (sfxRoutineNoiseborder+1),a
    

readData:
	ld a,(ix+0)		;read block type
	or a
	jr nz,readDatasound
	pop iy
	ei
	jp SoundEnd

readDatasound:
	ld c,(ix+1)		;read duration 1
	ld b,(ix+2)
	ld e,(ix+3)		;read duration 2
	ld d,(ix+4)
	push de
	pop iy

	dec a
	jr nz,sfxRoutineNoise



;this routine generate tone with many parameters
sfxRoutineTone:
	ld e,(ix+5)		;freq
	ld d,(ix+6)
	ld a,(ix+9)		;duty
	ld (sfxRoutineToneduty+1),a
	ld hl,0
    
sfxRoutineTonel0:
	push bc
	push iy
	pop bc
sfxRoutineTonel1:
	add hl,de
	ld a,h
sfxRoutineToneduty:
	cp 0
	sbc a,a
	and 16
sfxRoutineToneborder:
	or 0
	out ($fe),a
#line 78                
	dec bc
	ld a,b
	or c
	jr nz,sfxRoutineTonel1

	ld a,(sfxRoutineToneduty+1)
	add a,(ix+10)	;duty change
	ld (sfxRoutineToneduty+1),a

	ld c,(ix+7)		;slide
	ld b,(ix+8)
	ex de,hl
	add hl,bc
	ex de,hl

	pop bc
	dec bc
	ld a,b
	or c
	jr nz,sfxRoutineTonel0

	ld c,11
nextData:
	add ix,bc		;skip to the next block
	jr readData



;this routine generate noise with two parameters
sfxRoutineNoise:
	ld e,(ix+5)		;pitch

	ld d,1
	ld h,d
	ld l,d
sfxRoutineNoisel0:
	push bc
	push iy
	pop bc
sfxRoutineNoisel1:
	ld a,(hl)
	and 16
sfxRoutineNoiseborder:
	or 0
	out ($fe),a
	dec d
	jr nz,sfxRoutineNoisel2
	ld d,e
	inc hl
	ld a,h
	and $1f
	ld h,a
sfxRoutineNoisel2:
	dec bc
	ld a,b
	or c
	jr nz,sfxRoutineNoisel1

	ld a,e
	add a,(ix+6)	;slide
	ld e,a

	pop bc
	dec bc
	ld a,b
	or c
	jr nz,sfxRoutineNoisel0

	ld c,7
	jr nextData

Finally, you need to run beepfx, and compile just the sound data to asm.

You'll get something like this:

Code:
soundEffectsData
	dw .sfx0

.sfx0
	db #01
	dw #0032,#0064,#01f4,#ffec,#0080
	db #00

This needs some massaging to work. Change "soundEffectsData" to "soundEffectsData:"
Change "." to "soundEffectsData" And make labels have a : on the end.
Search and replace "db" with "defb"
Search and replace "dw" with "defw"
Replace # with $
All done!

Worked example:

Code:
soundEffectsData:
	defw soundEffectsDatasfx0
	defw soundEffectsDatasfx1

soundEffectsDatasfx0:
	defb $01
	defw $0032,$0064,$01f4,$ffec,$0080
	defb $00
soundEffectsDatasfx1:
	defb $01
	defw $0014,$0190,$00c8,$0005,$0110
	defb $01
	defw $001e,$0190,$00c8,$0008,$0110
	defb $00

you can then save this as something lime soundata.asm and #'include this file into the sound routine listed above. Call with sound (n) for the sound number.

Question about the Heap

Posted by: LCD - 2012-05-30, 09:19 AM - Forum: Help & Support - Replies (4)

Hi Boriel, just following easy question:
If I use a heap of 256 bytes, where it is put into memory? I want to know where I cannot put any binary data.
Is this 65535-heapsize?
Edit: May this be problematic if I page the heap out? Is there a possibility that we can put the heap at a selected memory area (e.g. a buffer created with DEFB's) at program start (I know that changing it may crash the program).

Pac Man Project

Posted by: britlion - 2012-05-27, 06:13 PM - Forum: Gallery - Replies (17)

	Clearly not finished, but I wanted feedback on how it feels. I spent /ages/ getting complex ghost behaviour right. Compare with CDS gobble a ghost, for example. <!-- m --><a class="postlink" href="http://dl.dropbox.com/u/4903664/DemoMan.tzx">http://dl.dropbox.com/u/4903664/DemoMan.tzx</a><!-- m --> (Yes, I know you can't die. Or eat ghosts. Yes, I know it breaks on level 2)

U-Boot hunt

Posted by: LCD - 2012-05-27, 08:47 AM - Forum: Gallery - Replies (5)

Another game finished and waiting for the music. It is one of the "lost games" from my homepage, rewritten and optimised from HiSoft BASIC to ZXBC. Some new stuff also added like a big explosion animation where the frames are compressed with MegaLZ and decompressed while playback. Also Border-effect added on the start screen, but only correctly working on Spectrum 128 in 48K or USR0 mode (In 128K BASIC the border jumps up and down, also it looks that the Spectrum is a bit slower), so DivIDE-users will load it right on their 128K.

.png u-boothunt.png (Size: 1.27 KB / Downloads: 4,464)
The goal is to find a nazi u-boot (submarine) and hit it with a depthcharge. You do not know where the sub is, but you know the distance between explosion and the sub. Easy? I don't think so because there is a limited number of Deptcharges and the sub moves constantly.
Okay, it is not a big game and not so good as Earthraid, but I wanted to release it to not have that many MIA titles in my portfolio.

New game: Earthraid

Posted by: LCD - 2012-05-26, 08:09 PM - Forum: Gallery - Replies (35)

	Earthraid.png (Size: 3.03 KB / Downloads: 7,545) Cooming soon: "EARTHRAID". This is a game published in 1986 for the Commodore C64. I made a Spectrum conversion of it. Its allready finished, but waiting now for a soundtrack.

output ASM

Posted by: britlion - 2012-05-02, 11:02 AM - Forum: Bug Reports - Replies (7)

Not sure if this is a bug, per se - but it is certainly a bit ugly.

This even survived the peephole optimizer.

Input Basic:

IF myCurrentVector = %1000 then

Output assembly:

ld a, (ix+9)
sub 8
sub 1
jp nc, __LABEL56

Two subs in a row? And worse "Sub 1" instead of a dec?

It later tests:

IF myCurrentVector = %0001 then

as:
ld a, (ix+9)
dec a
sub 1
jp nc, __LABEL63

And I'm not even convinced that's the same test as "equal to x" Surely that's testing "If myCurrentVector>x" anyway?

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