以mips(程序集)排序数组

时间:2013-10-06 18:45:12

标签: arrays sorting assembly mips

我在使用mips的课堂学习集会中。我正在研究一组数字,我认为我的方法正常,但只是有点麻烦。我不知道怎样检查我什么时候完全排序。我使用一种非常基本的方法进行排序,但这就是我们迄今为止学到的所有内容。此外,我不知道如何输出数字来检查它是否已排序。我习惯了Java,所以这样的组装有点让我旋转。这是我到目前为止的代码:

    .text
    .globl main
main:       la  $a0, Array             # sets the base address of the array to $a0
loop:       lw  $t0, 0($a0)             # sets $t0 to the current element in array
            lw  $t1, 4($a0)         # sets $t1 to the next element in array
            blt $t1, $t0, swap      # if the following value is greater, swap them
            addi    $a0, $a0, 4     # advance the array to start at the next location from last time
            j   loop                  # jump back to loop so we can compare next two elements

swap:       sw  $t0, 4($a0)         # store the greater numbers contents in the higher position in array (swap)
            sw  $t1, 0($a0)         # store the lesser numbers contents in the lower position in array (swap)
            li  $a0, 0                 # resets the value of $a0 back to zero so we can start from beginning of array
            j   loop                  # jump back to the loop so we can go through and find next swap

            .data

Array:      .word   14, 12, 13, 5, 9, 11, 3, 6, 7, 10, 2, 4, 8, 1 

感谢任何帮助人员!

3 个答案:

答案 0 :(得分:3)

This link说明如何在QTSPIMMARS等MIPS模拟器中打印到屏幕。

至于代码,有一些错误。第li $a0, 0行正在覆盖初始la $a0, Array指令所完成的工作,因为li正在将数组的基址设置为0.相反,您应该移动la指令进入循环,以便在迭代整个数组后$a0正确地重置为Array的基址,并删除li指令。您还需要在程序完成排序时添加条件。我建议进行以下修订(使用SPIM测试):

main:
    la  $t0, Array      # Copy the base address of your array into $t1
    add $t0, $t0, 40    # 4 bytes per int * 10 ints = 40 bytes                              
outterLoop:             # Used to determine when we are done iterating over the Array
    add $t1, $0, $0     # $t1 holds a flag to determine when the list is sorted
    la  $a0, Array      # Set $a0 to the base address of the Array
innerLoop:                  # The inner loop will iterate over the Array checking if a swap is needed
    lw  $t2, 0($a0)         # sets $t0 to the current element in array
    lw  $t3, 4($a0)         # sets $t1 to the next element in array
    slt $t5, $t2, $t3       # $t5 = 1 if $t0 < $t1
    beq $t5, $0, continue   # if $t5 = 1, then swap them
    add $t1, $0, 1          # if we need to swap, we need to check the list again
    sw  $t2, 4($a0)         # store the greater numbers contents in the higher position in array (swap)
    sw  $t3, 0($a0)         # store the lesser numbers contents in the lower position in array (swap)
continue:
    addi $a0, $a0, 4            # advance the array to start at the next location from last time
    bne  $a0, $t0, innerLoop    # If $a0 != the end of Array, jump back to innerLoop
    bne  $t1, $0, outterLoop    # $t1 = 1, another pass is needed, jump back to outterLoop

请务必查看this link以获取有关每条MIPS指令的其他示例和解释。

答案 1 :(得分:1)

直接编组是一种痛苦。我所做的是从一个算法(伪代码或实际代码)开始,然后系统地翻译,就好像我是一个编译器。我会忽略输入和输出的东西,并专注于一个排序的函数。

你会像C一样打电话给高级别的语言:

insertionsort(data, N);

其中data是整数数组,N是元素数(在机器级别没有大小属性​​)。

由于该函数不调用任何内容,因此不需要堆栈帧。遵守使用$t寄存器的标准MIPS约定,这样您就不会破坏任何其他人依赖的内容,并按顺序在$a0$a1中传递参数。

第1步:获取算法。这是来自[Wikipedia] [1]的插入排序:

i ← 1
while i < length(A)
    x ← A[i]
    j ← i - 1
    while j >= 0 and A[j] > x
        A[j+1] ← A[j]
        j ← j - 1
    end while
    A[j+1] ← x
    i ← i + 1
end while

第2步:粘贴到文本文件中,将所有行转换为注释并系统地转换为汇编。我使用模板来完成诸如循环之类的事情,这些模型可以帮助我完成编码(参见我的free book示例)。我会在这里给出成品;要调用它,您需要将数组的起始地址放入$a0,其大小放在$a1中,然后jal insertionsort

# algorithm for insertion sort
# from https://en.wikipedia.org/wiki/Insertion_sort
# usage: insertionsort (a,N)
# pass array start in $a0, size in elements, N in $a1
# Philip Machanick
# 30 April 2018

            .globl insertionsort

            .text

# leaf function, no stack frame needed
# Registers:
#   $a0: base address; $a1: N
#   $t0: i
#   $t1: j
#   $t2: value of A[i] or A[j]
#   $t3: value of x (current A[i])
#   $t4: current offset of A[i] or A[j] as needed
insertionsort:
# i ← 1
       li $t0, 1
# while i < N
       j Wnext001        # test before 1st iteration
Wbody001:                # body of loop here
      sll $t4, $t0, 2    # scale index i to offset
      add $t4, $a0, $t4  # address of a[i]
#     x ← A[i]
      lw $t3, 0($t4)
#     j ← i - 1
      addi $t1, $t0, -1
#     while j >= 0 and A[j] > x
       j Wnext002        # test before 1st iteration
Wbody002:                # body of loop here
#         A[j+1] ← A[j]
          sll  $t4, $t1, 2        # scale index j to offset
          add $t4, $a0, $t4       # address of a[j]
          lw $t2, 0($t4)          # get value of A[j]
          addi $t4, $t4, 4        # offset of A[j+1]
          sw $t2, 0($t4)          # assign to A[j+1]
#         j ← j - 1
          addi $t1, $t1, -1
#     end while
Wnext002: # construct condition, j >= 0 and A[j] > x
          blt $t1, $zero Wdone002 # convert to: if j < 0 break from loop #####
          sll  $t4, $t1, 2        # scale index j to offset
          add $t4, $a0, $t4       # address of a[j]
          lw $t2, 0($t4)          # A[j]
          bgt $t2, $t3, Wbody002  # no need to test j >= 0, broke from loop already if false
Wdone002:                         # branch here to short-circuit and
#     A[j+1] ← x
          add  $t4, $t1, 1        # scale index j+1 to offset
          sll  $t4, $t4, 2        # scale index j to offset
          add $t4, $a0, $t4       # address of a[j+1]
          sw $t3, 0($t4)          # A[j+1] becomes x
#     i ← i + 1
          addi $t0, $t0, 1
# end while
Wnext001: blt $t0,$a1, Wbody001  # i < N easy this time
          jr $ra                 # return to caller

比其他示例更长 - 但如果从算法开始并翻译,则不太可能出错。如果汇编程序遵守.globl指令,这可以放在一个单独的文件中,这使得该名称在其他文件中可见。

[1]:https://en.wikipedia.org/wiki/Insertion_sort - 实际上来自Cormen,Thomas H。; Leiserson,Charles E。; Rivest,Ronald L。; Stein,Clifford(2001)。 &#34;第2.1节:插入排序&#34;。算法简介(第2版)。麻省理工学院出版社和McGraw-Hill。第15-21页

答案 2 :(得分:-1)

。数据

值:.word 0x3

数组:.word 0x14,0x12,0x13,0x05

的.text

.globl main

main:la $ a0,Array

   lw  $t3,value  

l1:lw $ t0,0($ a0)

   lw  $t1, 4($a0)     

   blt $t1, $t0, swap   

   addi    $a0, $a0, 4

   addi $t3,$t3,-1     

   bne  $t3,$zero,l1

   jr $ra

交换:sw $ t0,4($ a0)

    sw  $t1, 0($a0)    

    j   l1