MIPS finding the largest two integers of 3 inputs

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October 24th, 2011, 12:54 PM

kevinj1977

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MIPS finding the largest two integers of 3 inputs

Hi folks,
I am playing with some MIPS assembly language and am stuck on how to find the largest of 3 integers entered. I have figured out how to compare the first 2 with the branch instructions but I am unsure of the most efficient way to compare all 3. Here is what I had put together for code. The bge calls are where I am trying to figure out the best way to compare all 3. the first bge compares the first 2. Anyone have any insight?

Code:

.text
.align 2 
.globl main 

main: 
# this program prints out the largest two of three numbers input 

li $v0, 4 
la $a0, prompt1 
syscall 
li $v0, 5 # read keyboard into $v0 (number x is number to test) 
syscall 
move $t0,$v0 # first number in $t0 

li $v0, 4 
la $a0, prompt2 
syscall 

li $v0, 5 # read keyboard into $v0 (number x is number to test) 
syscall 
move $t1,$v0 # second number in $t1 

li $v0, 4 
la $a0, prompt3 
syscall 

li $v0, 5 # read keyboard into $v0 (number x is number to test) 
syscall 
move $t2,$v0 # third number in $t2 

bge $t1, $t0, L1 
move $t1, $t0 # largest number in $t1 

bge $t2, $t1, L1 
move $t2, $t1

L1: 
li $v0, 4 # print answer 
la $a0, answer 
syscall 

li $v0, 1 # print integer function call 1 
move $a0, $t1 # integer to print 
syscall 

end: jr $ra 

.data 
prompt1: .asciiz "Enter the first number " 
prompt2: .asciiz "Enter the second number " 
prompt3: .asciiz "Enter the third number " 
answer: .asciiz "The largest number is "

October 24th, 2011, 06:03 PM

E-Oreo

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Code:

# effectively these two lines do: $t1 = max($t0, $t1)
bge $t1, $t0, CMP2
move $t1, $t0

CMP2:
# effectively these two lines do: $t1 = max($t2, $t1)
bge $t1, $t2, L1 
move $t1, $t2

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October 24th, 2011, 06:50 PM

kevinj1977

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Kudos to you. I have updated the code to reflect your suggestion and tested it successfully. Makes sense to me now. The next piece I am interested in adding would be to find the 2 largest of the 3 integers entered. My thoughts would be to add another CMP3 statement and compare them again minus the largest we've already identified and stored? Would a sort type statement work better than doing these separately? Here is what the updated code looks like after adding your suggestion:

Code:

.text 
.align 2 
.globl main 

main: # this program prints out the largest two of three numbers input 

li $v0, 4 
la $a0, prompt1 
syscall 

li $v0, 5 # read keyboard into $v0 (number x is number to test) 
syscall move $t0,$v0 # first number in $t0 

li $v0, 4 la $a0, prompt2 
syscall 

li $v0, 5 # read keyboard into $v0 (number x is number to test) 
syscall 
move $t1,$v0 # second number in $t1 

li $v0, 4 la $a0, prompt3 
syscall 

li $v0, 5 # read keyboard into $v0 (number x is number to test) 
syscall 
move $t2,$v0 # third number in $t2 

bge $t1, $t0, CMP2 
move $t1, $t0 # largest number in $t1 

CMP2: 
bge $t1, $t2, L1 
move $t1, $t2 

L1: 
li $v0, 4 # print answer 
la $a0, answer 
syscall 

li $v0, 1 # print integer function call 1 
move $a0, $t1 # integer to print 
syscall 

end: jr $ra 

.data 

prompt1: .asciiz "Enter the first number " 
prompt2: .asciiz "Enter the second number " 
prompt3: .asciiz "Enter the third number " 
answer: .asciiz "The largest number is "

MIPS finding the largest two integers of 3 inputs

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