Assignment 4

3 minute read

Due: by the end of the calendar day on Tuesday, October 1, 2024

A Python program with functions and arrays

The following Python program utlizes a function that doubles every item in a list. It is spread across four different functions.

#test out double_items on two different lists
def main():
    list1 = [54,26,93,17,77,31,44,55,20]
    length1 = 9
    list2 = [9,8,7,6,5]
    length2 = 5
    double_items(list1,length1)
    double_items(list2,length2)
    print_list(list1,length1)
    print()
    print_list(list2,length2)
    return

#double a single value
def double_value(val):
    result = val+val
    return result

#double all items in a list
def double_items(a_list, list_length):
    i = 0
    while i < list_length:
        a_list[i] = double_value(a_list[i])
        i = i + 1
    return

#print a list with one item per line
def print_list(a_list,list_length):
    i = 0
    while i < list_length:
        print(a_list[i])
        i = i + 1
    return

main()

Here’s the output you get when you run it in the console:

A start to translating the Python program into MIPS

Here’s an attempt to translate the program into MIPS. The main, double_value, and print_list procedures are finished, but you will need to finish implementing the double_items procedure.

.data

   list1: 54,26,93,17,77,31,44,55,20
   length1: 9
   list2: 9,8,7,6,5
   length2: 5

   newline: .asciiz "\n"

.text

###############BEGIN main###############
main:
   la $a0, list1
   lw $a1, length1
   jal double_items
   
   la $a0, list2
   lw $a1, length2
   jal double_items
   
   la $a0, list1
   lw $a1, length1
   jal print_list
   
   li $v0, 4 #code for printing a string
   la $a0, newline
   syscall
   
   la $a0, list2
   lw $a1, length2
   jal print_list
   
   j exit_program
###############END main###############   

   
###############BEGIN double_value###############   
double_value:
   add $v0, $a0, $a0
   jr $ra
###############END double_value###############


###############BEGIN double_items###############
#this doesn't do anything yet, it just
#jumps back to the calling procedure
#you must implement this function to work
#like the double_items function in the
#Python program
double_items:
   jr $ra
###############END double_items###############


###############BEGIN print_list###############
print_list:
   move $t0, $a0 #$a0 is the list address
   move $t1, $a1 #$a1 is the list length
   li $t2, 0 #loop counter i

print_list_loop:   
   bge $t2, $t1, print_list_end #exit loop if i >= list length
   
   sll $t4, $t2, 2 #multiply loop counter by 4 to get memory offset
   add $t3, $t0, $t4 #add base address of list and memory offset
   
   lw $a0, 0($t3) #load a_list[i]
   li $v0, 1 #code for printing an integer
   syscall
   
   li $v0, 4 #code for printing a string
   la $a0, newline
   syscall
   
   addi $t2, $t2, 1 #increment loop counter
   
   b print_list_loop
   
   
print_list_end:
   jr $ra
###############END print_list###############
   
exit_program:   

Assignment

Finish translating the double_items function into a MIPS procedure.

The translation should do the following (in order of priority):

allow the function to behave just the same way as the Python program
call the double_value procedure from inside the double_items procedure
inside double_items, use the stack (with $sp) to save $ra and to make sure you restore any $s registers that you use to their values that they had before the procedure started

Grading

This is an 8-point assignment. See the rubric from the syllabus, with the following exception:

The full 8 points will be for correct behavior with proper use of the stack and a call to double_value from within double_items. You can get 7 points if it behaves correctly and you have utilized at least one of double_value and the stack. You can get 6 points for something that behaves correctly even if it uses neither of double_value nor the stack. You will get 5 points for significant progress towards the solution, even if it produces incorrect results.

What to turn in

Turn in the following items

Your .asm file which contains your MIPS program
A .txt file (you can use Notepad, TextEdit, or even Visual Studio Code) where you paste in a sample run of your program that shows how it worked when you ran it in MARS

Where to turn it in

Submit your files to the Assignment 4 hand-in form on Blackboard.

Instructor

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