Mark: 34 revision(s)

2008-11-03T05:18:40Z

34 revision(s)

New page

==How long does it take to execute an addition (+) operation in C?==

===Information===

*Variable sizes
Int : -2,147,483,648 to 2,147,483,647
Long : -2,147,483,648 to 2,147,483,647
Short : -32,768 to 32,767
float : (+-)1.175494e-38 to (+-)3.402823e+38
double: (+-)2.225074e-308 to (+-)1.797693e+308

*Clock function
:*In the file 'time.h'
:*Use type 'clock_t'

===Expectation===
* The time of running time would be effected by the range of each type

====Expected order by the speed====
*1: short
*2: int and long
*3: float
*4: double

===Testing codes===
====Sample1====
* Codes
#define _CRT_SECURE_NO_DEPRECATE
#include <stdio.h>
#include <time.h>
int main(void)
{
int a;
int b=1;
clock_t t0 = clock();
for (a=1; a<1000; a++) {
b = b+a;
}
printf("%d\n", b);
printf("%d", clock() - t0);
return 0;
}
* Results
b = 499501
time = 0
*discussion
The time is too small -> more calculations are needed

====Sample2====
* Codes
#define _CRT_SECURE_NO_DEPRECATE
#include <stdio.h>
#include <time.h>
int main(void)
{
int a;
int b=1;
clock_t t0 = clock();
for (a=1; a<1000000000; a++) {
b = b+a;
}
printf("%d\n", b);
printf("%d", clock() - t0);
return 0;
}
* Results
b = -1243309311
Time = 3475
*Discussion
B = -1243309311 because B is bigger than the bigger than 2,147,483,647(maximum int value) -> All calculation should be calculated with short size (the smallest variable: -32,768 to 32,767)

====Sample3====
* Codes
#define _CRT_SECURE_NO_DEPRECATE
#include <stdio.h>
#include <time.h>
int main(void)
{
int a, b;
int c=0;
clock_t t0 = clock();
for (a=1; a<32767; a++) {
for(b=1; b<32767; b++) {
c = c+a-b;
}
}
printf("c needs to be 0 = %d\n", c);
printf("time = %d", clock() - t0);
return 0;
}
* Results
c = 0
Time = 3892
*discussion
While calculate the answer, 'c' goes over 32767, yet this looks fine.

====Sample4(final)====
* Codes
#define _CRT_SECURE_NO_DEPRECATE
#include <stdio.h>
#include <time.h>
int main(void)
{
int a, b, c=1, d=0;
clock_t t0 = clock();
for (a=1; a<32767; a++) {
for(b=1; b<32767; b++) {
d=d+c;
}
c=c*-1;
}
printf("c needs to be 32767 = %d\n", d);
printf("time = %d", clock() - t0);
return 0;
}
* Results
c = 32767
Time = 2627
*Discussion
:* This example includes ‘*’, ‘+’, and ’-‘ which increase the processing time, yet this lab suggests to use addition (+) operation.

===Testing===
====Vista(Visual Studio 2008)====
Type Int long Short Float Double
--------------------------------------
Test1 2346 2334 3011 9074 9397
Test2 2463 2339 3251 9295 9122
Test3 2447 2343 3086 9029 9054
Test4 2337 2373 2981 9056 9053
Test5 2346 2336 2991 9026 9057
--------------------------------------
AVG 2388 2345 3064 9096 9137
*Discussion
:*The results are not always same.
::*The speed of a programme is may affected by the condition of the CPU and other running programmes.
:*‘int’ and ‘long’ are similar, and are the fastest.
:*’short’ is little slower than ‘int’ and ‘long’
:*’float’ and ‘double’ are similar, and about 3 times slower than ‘short’
::*Data types, ‘float’ and ‘double’, have different range, but floating point data may types show same processing speed.

====Vista(CYGWIN)====
Type Int long Short Float Double
--------------------------------------
Test1 3588 3541 6615 5102 5085
Test2 3540 3603 6723 5132 5132
Test3 3557 3603 6614 5070 5085
Test4 3541 3525 6693 5070 5101
Test5 3572 3556 6661 5116 5085
--------------------------------------
AVG 3560 3566 6661 5098 5098
* Discussion
:*‘int’ and ‘long’ are similar, and are the fastest.
:*’float’ and ‘double’ are similar, and are slower than ‘int’ and ‘long’
::*The difference between ‘float’ and ‘double’, and ‘int’ and ‘long’ are smaller than in Visual Studio 2005.
:*’Short’ is slower than ‘float and ‘double which is unexpected.
::*The type, ’short’, may uses difference processing method than ‘int’, and ‘long’

==Conclusion==
*The speed of a programme is may changeable by condition of the CPU and other running programmes.
*Same range data types may show similar processing speed (e.g. int and long).
*Floating point data types may show similar processing speed (e.g. float and double).
*This report suggests some rules with the time, but these rules could be different in other conditions. (e.g. 64bit windows, Linux, different cpus, etc)

SE250:lab-1:dcho040 - Revision history

Mark: 34 revision(s)