New size coding contest "ZX Spectrum effect"
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New size coding contest "ZX Spectrum effect"
(I just copied his post into this new thread)
PhiBrizzo proposes a new competition. Very old, from ZX Spectum forum.
Goal: draw black and white 1x1 pixel chessboard on full screen.
Rules:
- must run on ROMv5+
- 32KB+ machines
- no SYS functions
- all tricks allowed
The winner is: shortest gt1 file.
PhiBrizzo proposes a new competition. Very old, from ZX Spectum forum.
Goal: draw black and white 1x1 pixel chessboard on full screen.
Rules:
- must run on ROMv5+
- 32KB+ machines
- no SYS functions
- all tricks allowed
The winner is: shortest gt1 file.
- Attachments
-
- images.png (3.67 KiB) Viewed 9705 times
Re: New size coding contest "ZX Spectrum effect"
Here is mine solution (not sure, if screen is correct this way?):
Code: Select all
int main(void)
{
int x,y;
for (x=0;x<160;x+=2) {
for (y=0;y<120;y+=2) {
screenMemory[y-1][x-1] = 0;
screenMemory[y][x] = 0xff;
}
}
}
Code: Select all
-rw-rw-r--@ 1 ich staff 141 13 Mär 17:53 Makefile
-rw-r--r--@ 1 ich staff 265 13 Mär 18:09 zxs.c
-rw-r--r-- 1 ich staff 107 13 Mär 18:09 zxs_v5a.gt1
- Attachments
-
- zxs.zip
- (3 KiB) Downloaded 328 times
-
- Bildschirmfoto 2024-03-13 um 18.10.05.png (61.4 KiB) Viewed 9704 times
Re: New size coding contest "ZX Spectrum effect"
Hello
In Your code is little error.
In loops you must started from x=1 and y=1. Because you did [x-1][y-1].
And first index = x - 1 = -1. The same for y.
Okay, we have the first player, who next?
In Your code is little error.
In loops you must started from x=1 and y=1. Because you did [x-1][y-1].
And first index = x - 1 = -1. The same for y.
Okay, we have the first player, who next?
Re: New size coding contest "ZX Spectrum effect"
You have to be careful when specifying rules and then saying all tricks allowed.
vCPU Code Size: 20 bytes
GT1 Size: 31 bytes
- Overwrites offscreen memory
- Crashes when it wraps back around to address 0x0000
I wrote a second version in native code that only runs in emulation, (unless you burn a ROM), does not use SYS functions and uses no vCPU instructions and does not produce a GT1 file, hence:
vCPU Code Size: 0 bytes
GT1 Size: 0 bytes
P.S. If you want to see the native version I'll post it here.
*Edit* corrected an error in starting pixel
Code: Select all
chess EQU 0x0200
addr EQU 0x30
addr DW 0x0800
chess LD addr + 1
ADDW addr
ADDI 1
ANDI 1
ADDI 0x3F
POKE addr
LDW addr
ADDI 1
STW addr
BRA chess
GT1 Size: 31 bytes
- Overwrites offscreen memory
- Crashes when it wraps back around to address 0x0000
I wrote a second version in native code that only runs in emulation, (unless you burn a ROM), does not use SYS functions and uses no vCPU instructions and does not produce a GT1 file, hence:
vCPU Code Size: 0 bytes
GT1 Size: 0 bytes
P.S. If you want to see the native version I'll post it here.
*Edit* corrected an error in starting pixel
Re: New size coding contest "ZX Spectrum effect"
Hello
About Your program, i can only say: You Win!
This is my example:
40 bytes code, 46 bytes GT1.
Ah, You are right.You have to be careful when specifying rules and then saying all tricks allowed.
About Your program, i can only say: You Win!
This is my example:
Code: Select all
_CPU v5.vcpu
_VAR FC_Main #$20A0
_RUN FC_Main
; -----------------------
_VAR ScrAdr #129
_VAR ScrAdrH #130
_ORG FC_Main
_LAB #3
LDWI #$0800
STW ScrAdr
_LAB #1
LD ScrAdrH
XORW ScrAdr
ANDI #1
BEQ #2
LDI #63
_LAB #2
POKE ScrAdr
INC ScrAdr
LD ScrAdr
XORI #160
BNE #1
ST ScrAdr
INC ScrAdrH
LD ScrAdrH
XORI #128
BNE #1
;HALT ; no SYS function ;)
BRA #3
This is not nessesry. I dont know native language.P.S. If you want to see the native version I'll post it here.
Re: New size coding contest "ZX Spectrum effect"
I disasembled Your program.
You and at67 used very smart trick: if color is biger that 63 then is black.
Congratulations!
You and at67 used very smart trick: if color is biger that 63 then is black.
Congratulations!
Re: New size coding contest "ZX Spectrum effect"
I saw this in at67's code above in this thread.
My challenge was to make the C compiler produce the optimal code.
Note that a color bigger than 63 is not always black.
The vga output only uses the low 6 bits. The two 2 bits are ignored.
Re: New size coding contest "ZX Spectrum effect"
What I did was pretty simple and somewhat sneaky:
1) Only one loop with no comparisons.
2) You can treat screen memory as one complete non-fragmented segment, i.e. write pixels to the 96 byte offscreen/hidden segments.
3) Toggle the pixel colour using a combination of the low byte and high byte of the incrementing address, this gives us the alternate colour pixels in x and y.
4) Alternate between 0x00/black and 0x3F/white for the pixel colour without branching.
5) Let the code run rampant once it's finished all pixels, i.e. no sanity/safety checks.
6) Use static initialisation of variables, (which my assembler supports), rather than wasting LDI/LDWI instructions in code.
For these kinds of competitions you really need to be more explicit in your rules, or people will have a field day, i.e. I wrote a native version that satisfies the current rules and produces a gt1 file of 0 bytes...
A set of potentially less exploitive rules could go as follows:
- Must produce a physical gt1 file.
- Must run 100% vCPU code, (assembled, compiled or interpreted).
- Must not call SYS functions.
- Must run on <= ROMv5a and 32KByte RAM hardware.
- Must visit all 160x120 pixels.
- Must not write to any offscreen memory.
- Must not mess with the video indirection table to make the onscreen video size smaller or allow for pixel duplication.
- Must produce a stable image and not crash.
- Winner is decided by smallest vCPU code size AND smallest .GT1 file size, with priority going to vCPU code size.
Even with these rules I would hope someone would find a loophole, as that's where the fun really is!