Question

I have to do insertion sort of numbers in NASM. I have a file which generates random numbers and generate output file with numbers in binary form. My program loads this as input file and should give output with numbers sorted using insertion sort, also in binary form.

My code:

; Template assembler source file

section .text
global _start

_start:
    ; put your code here
    mov eax, 3
    mov ebx, 0
    mov ecx, array
    mov edx, 4*32768
    int 80h
    mov [fileLength], eax   
    shr eax,2
    dec eax
    mov [number], eax



    mov ebx, 1 
    outerloop:
        mov ecx,[array + 4*ebx]
        mov [item],ecx 

        mov ecx,ebx 
        interloop:
        mov edx,ecx 
        dec edx
        mov esi, [array + 4*edx]
        cmp esi,[array + 4*ecx]     
        jb koniec 
            mov eax,[array + 4*edx]
            mov [array + 4*ecx],eax 
        loop interloop
        koniec:

    mov edx,[item]
    mov [array + 4*ecx],edx 

    inc ebx
    cmp ebx,[number] 
    jne outerloop


    mov eax, 4
    mov ebx, 1
    mov ecx, array
    mov edx, [fileLength]
    int 80h



    ; exit to linux
    mov eax,1
    mov ebx,0
    int 80h

; initialized data section
; use directives DB (byte), DW (word), DD (doubleword), DQ (quadword)
section .data

; uninitialized data section
; use directives RESB (byte), RESW (word), RESD (doubleword), RESQ (quadword)
section .bss
    fileLength resd 1   
    number resd 1   

    array resd 32768
    item resd 1

Pseudo code that I used to write insertion sort:

for i ← 1 to i ← length(A)-1
   {
     // A[ i ] is added in the sorted sequence A[0, .. i-1]
     // save A[i] to make a hole at index iHole
     item ← A[i]
     iHole ← i
     // keep moving the hole to next smaller index until A[iHole - 1] is <= item
     while iHole > 0 and A[iHole - 1] > item
       {
         // move hole to next smaller index
         A[iHole] ← A[iHole - 1]
         iHole ← iHole - 1
       }
     // put item in the hole
     A[iHole] ← item
   }

source: http://en.wikipedia.org/wiki/Insertion_sort

My knowledge about it is pretty small and I don’t know what goes wrong. It sometimes sorts first few numbers but the rest of them is not sorted correctly.

Answer 1

You have to change the line

cmp esi, [array + 4*edx]

to

cmp esi, [item]

and remove dec eax before your outerloop. It should work.