I am rewriting my C Kruskal algorithm in Assembly language. For fun and learning purposes :icon_mrgreen:
I am running into a problem with my QSORT call here... my program goes into qsort, never to return.
I spent a lot of time debugging and I don't see where my problem is. I think my memory is ok. I used both a static array and dynamic memory and I got the same results.
It calls compare once, it loads the proper values, compares them well. Then it goes back into QSORT and boom!
The code is here :
https://github.com/mitchi/Kruskal-ASM/blob/master/kruskal.asm
https://github.com/mitchi/Kruskal-ASM
Try to not destroy content of register ebx in the cmp proc!
It works... !!!!!
!!!!
I'm so happy.
So basically I have to save the contents of certain registers? Which one do I have to save between calls?
EAX, ECX, EDX can be trashed
EBX, ESI, EDI, EBP must be preserved
if you set the direction flag, you should leave it cleared before calling an API function
anybodies guess as to whether FPU or XMM registers are preserved in API calls - lol
thanks
:biggrin:
There are times when I feel like a voice crying in the wilderness, after having published technical data to support the Intel ABI (what registers etc ...) over and over and over (yawn) and over and over and over (ZZZZZzzzzzzz_______ .......) again and again and again we still fail to connect that if you want to write reliable code that works, you preserve the right registers in and out of an algorithm.
i made that post with a single stroke of a hot-key :lol:
Quote from: dedndave on January 13, 2013, 02:09:51 PM
i made that post with a single stroke of a hot-key :lol:
Smart :)
Hi mitchi,
Quote from: mitchi on January 14, 2013, 07:47:05 PM
Smart :)
Dave is smart all the time. But joke apart: you should read the Application Binary Interface (ABI). You can find a lot of remarks to that in Agner Fog's manuals: http://agner.org/optimize/ (http://agner.org/optimize/)
Good luck!
Gunther
Hi mitchi,
A quick example :
.386
.model flat,stdcall
option casemap:none
include \masm32\include\windows.inc
include \masm32\include\kernel32.inc
include \masm32\include\msvcrt.inc
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\msvcrt.lib
CompareProc PROTO C :DWORD,:DWORD
strcmpX PROTO :DWORD,:DWORD
NUMB_OF_ELEMENTS equ 8
.data
str1 db 'Orange',0
str2 db 'Cherry',0
str3 db 'Strawberry',0
str4 db 'Apple',0
str5 db 'Fig',0
str6 db 'Apricot',0
str7 db 'Pear',0
str8 db 'Peach',0
StrTabl dd str1,str2,str3,str4,str5,str6,str7,str8
msg db 'List of fruits in alphabetical order',13,10
db '====================================',13,10,13,10,0
format1 db '%s',13,10,0
.code
start:
invoke crt_qsort,ADDR StrTabl,NUMB_OF_ELEMENTS,\
SIZEOF DWORD,ADDR CompareProc
call PrintArray
invoke ExitProcess,0
CompareProc PROC C USES esi edi arg1:DWORD,arg2:DWORD
mov ecx,arg1
mov edx,arg2
mov esi,DWORD PTR [ecx]
mov edi,DWORD PTR [edx]
mov ecx,1
mov edx,-1
@@:
add edx,ecx
movzx eax,BYTE PTR [esi+edx]
test eax,eax
jz _exit
cmp al,BYTE PTR [edi+edx]
je @b
sbb eax,eax
sbb eax,-1
; To sort an array in decreasing order, reverse the sense of
; greater than and less than in the comparison function :
;
; neg eax
_exit:
ret
CompareProc ENDP
PrintArray PROC uses esi ebx
mov ebx,NUMB_OF_ELEMENTS
mov esi,OFFSET StrTabl
invoke crt_printf,ADDR msg
@@:
invoke crt_printf,ADDR format1,DWORD PTR [esi]
add esi,4
dec ebx
jnz @b
ret
PrintArray ENDP
END start