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Question: Which is the best function to count the running time an algorithm?

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kohuke

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Question: Which is the best function to count the running time an algorithm?

Sep 10th, 2007

I have a program that will find the certain ammount of fibonacci numbers. And now i have the question which is the best code for counting time in fibonacci algorithm?
I have to find out how many numbers can my algorithm count in 1 minute?

the code:

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 Java Syntax (Toggle Plain Text) 
//rekursiivne algoritm
 
public class Fibo {
	//Fibonacci rekursiivse algoritmi põhiosa
	public static long fib(int n){
		if (n <= 2) return 1;//kui arv on väiksem kui kaks, siis tagastatakse "1"
	    else return fib(n-1) + fib(n-2);
	}
	public static void main(String[] args) {
		int N = Integer.parseInt(args[0]);//sisestus
		for(int i=2; i<=N;i++){//tsükkel, mida täidetakse, kuni nõudmised on rahuldatud
			System.out.println(i + ": " + fib(i));//väljatrükk
		}
 
	}
//rekursiivne algoritm

public class Fibo {
	//Fibonacci rekursiivse algoritmi põhiosa
	public static long fib(int n){
		if (n <= 2) return 1;//kui arv on väiksem kui kaks, siis tagastatakse "1"
	    else return fib(n-1) + fib(n-2);
	}
	public static void main(String[] args) {
		int N = Integer.parseInt(args[0]);//sisestus
		for(int i=2; i<=N;i++){//tsükkel, mida täidetakse, kuni nõudmised on rahuldatud
			System.out.println(i + ": " + fib(i));//väljatrükk
		}

	}

and the few time counting things i have found in google. So which one suits better or can you give me a general idea where to put it?
I heard from a friend that getMills function isn't really the right one

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 Java Syntax (Toggle Plain Text) 
long start = System.currentTimeInMillis();
goat();
long time = System.currentTimeInMillis() - start;
long start = System.currentTimeInMillis();
goat();
long time = System.currentTimeInMillis() - start;

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 Java Syntax (Toggle Plain Text) 
System.currentTimeMillis()
System.currentTimeMillis()

Many thanks to whom ever decides to answer

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Ezzaral

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Re: Question: Which is the best function to count the running time an algorithm?

Sep 10th, 2007

Well, you can use

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   long startTime = System.nanoTime();
   // ... the code being measured ...
   long estimatedTime = System.nanoTime() - startTime;
   long startTime = System.nanoTime();
   // ... the code being measured ...
   long estimatedTime = System.nanoTime() - startTime;

if you really think you need better than millisecond resolution.

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iamthwee

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Re: Question: Which is the best function to count the running time an algorithm?

Sep 10th, 2007

For measuring the relative execution times of alternate implementations, consider turning off the HotSpot compiler, using java -Xint. This will ensure a uniform environment for the entire duration of a program.

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kohuke

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Re: Question: Which is the best function to count the running time an algorithm?

Sep 11th, 2007

I'll try that java -xint thing (i usually do not use the command line to compile my code - eclipse does the work for me).
But i think that milliseconds will do fine. Thanks for the advice. i'll try that out as soon as possible.

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kohuke

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Re: Question: Which is the best function to count the running time an algorithm?

Sep 11th, 2007

well i treid couple of things out. And this time this placement of functions won't get me any errors, but i can't get the time to printed out. I know that i'm doing something wrong, can you please tell me what it is?

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
long startTime = System.nanoTime();
   // ... the code being measured ...
   long estimatedTime = System.nanoTime() - startTime;
long startTime = System.nanoTime();
   // ... the code being measured ...
   long estimatedTime = System.nanoTime() - startTime;

that didn't give me any output as well(when i places the system.out.print() command there), so i did a little bit searching in google and found some codes: http://forum.java.sun.com/thread.jsp...sageID=9462589 and and edit my code with those and those still didn't give me anything good.

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
//rekursiivne algoritm
 
public class Fibo {
	static final long NANO=1000L*1000*1000*1000;
 
	//long startTime=System.nanoTime();
 
	//Fibonacci rekursiivse algoritmi põhiosa
	public static long fib(int n){
		if (n <= 2) return 1;//kui arv on väiksem kui kaks, siis tagastatakse "1"
	    else return fib(n-1) + fib(n-2);
	}
 
	//long end = 10*NANO+System.nanoTime();
	//for(end<(System.nanoTime())){
	public static void main(String[] args) {
		long end = 10*NANO+System.nanoTime();
		while(end<System.nanoTime()){
 
			int N = Integer.parseInt(args[0]);//sisestus
			for(int i=2; i<=N;i++){//tsükkel, mida täidetakse, kuni nõudmised on rahuldatud
				System.out.println(i + ": " + fib(i));//väljatrükk
 
			}
			System.out.print(end);
		}
 
	}
}
 
	//startTime=startTime/10000000l;
	//long estimatedTime=System.nanoTime()-startTime;
	//System.out.(estimatedTime/10000000L);
//rekursiivne algoritm

public class Fibo {
	static final long NANO=1000L*1000*1000*1000;
	
	//long startTime=System.nanoTime();
	
	//Fibonacci rekursiivse algoritmi põhiosa
	public static long fib(int n){
		if (n <= 2) return 1;//kui arv on väiksem kui kaks, siis tagastatakse "1"
	    else return fib(n-1) + fib(n-2);
	}
	
	//long end = 10*NANO+System.nanoTime();
	//for(end<(System.nanoTime())){
	public static void main(String[] args) {
		long end = 10*NANO+System.nanoTime();
		while(end<System.nanoTime()){
		
			int N = Integer.parseInt(args[0]);//sisestus
			for(int i=2; i<=N;i++){//tsükkel, mida täidetakse, kuni nõudmised on rahuldatud
				System.out.println(i + ": " + fib(i));//väljatrükk
				
			}
			System.out.print(end);
		}

	}
}
	
	//startTime=startTime/10000000l;
	//long estimatedTime=System.nanoTime()-startTime;
	//System.out.(estimatedTime/10000000L);

the code looks messy now, but i hope you still understand it. And yes current setting it gives me time is 10 seconds, but i thought that before i start modyfing it any different way i tought that i'd try how it works.

Last edited by kohuke; Sep 11th, 2007 at 2:52 am. Reason: forgot something

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kohuke

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Re: Question: Which is the best function to count the running time an algorithm?

Sep 17th, 2007

So now i got a program that should work, meaning that showing the time elapsed of how long the program has run. But for some reason it won't print the time out

. Can you tell me please what i'm doing wrong??

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
//rekursiivne algoritm
 
public class Fibo {
 
	//Fibonacci rekursiivse algoritmi põhiosa
	public static long fib(int n){
		if (n <= 2) return 1;//kui arv on väiksem kui kaks, siis tagastatakse "1"
	    else return fib(n-1) + fib(n-2);
	}
	public static void main(String[] args) {
			long start=System.nanoTime();
			System.out.print(start);
			int N = Integer.parseInt(args[0]);//sisestus
			for(int i=2; i<=N;i++){//tsükkel, mida täidetakse, kuni nõudmised on rahuldatud
				System.out.println(i + ": " + fib(i));//väljatrükk
				System.out.println(System.nanoTime());
			}
			long end=System.nanoTime();
			long kulus=end-start;
			System.out.println(kulus);
		}
}
//rekursiivne algoritm

public class Fibo {

	//Fibonacci rekursiivse algoritmi põhiosa
	public static long fib(int n){
		if (n <= 2) return 1;//kui arv on väiksem kui kaks, siis tagastatakse "1"
	    else return fib(n-1) + fib(n-2);
	}
	public static void main(String[] args) {
			long start=System.nanoTime();
			System.out.print(start);
			int N = Integer.parseInt(args[0]);//sisestus
			for(int i=2; i<=N;i++){//tsükkel, mida täidetakse, kuni nõudmised on rahuldatud
				System.out.println(i + ": " + fib(i));//väljatrükk
				System.out.println(System.nanoTime());
			}
			long end=System.nanoTime();
			long kulus=end-start;
			System.out.println(kulus);
		}
}

In eclipse i get this kind of output:

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 Java Syntax (Toggle Plain Text) 
1
2
3
5
8
13
21
34
55
89
144
233
377
610
987
1597
2584
4181
6765
1
2
3
5
8
13
21
34
55
89
144
233
377
610
987
1597
2584
4181
6765

and using command line:

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System time is: 1822633765464
2: 1
1822634634848
3: 2
1822634931255
4: 3
1822635194137
5: 5
1822636747128
6: 8
1822638337833
7: 13
1822639893617
8: 21
1822641384868
9: 34
1822642854329
10: 55
1822644331891
11: 89
1822645816996
12: 144
1822647326126
13: 233
1822648884425
14: 377
1822651070457
15: 610
1822653201733
16: 987
1822654758076
17: 1597
1822656452146
18: 2584
1822658018267
19: 4181
1822660821696
20: 6765
1822662514928
Elapsed time: 29478048
System time is: 1822633765464
2: 1
1822634634848
3: 2
1822634931255
4: 3
1822635194137
5: 5
1822636747128
6: 8
1822638337833
7: 13
1822639893617
8: 21
1822641384868
9: 34
1822642854329
10: 55
1822644331891
11: 89
1822645816996
12: 144
1822647326126
13: 233
1822648884425
14: 377
1822651070457
15: 610
1822653201733
16: 987
1822654758076
17: 1597
1822656452146
18: 2584
1822658018267
19: 4181
1822660821696
20: 6765
1822662514928
Elapsed time: 29478048

So why cannot i see it in eclipse?

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kohuke

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Re: Question: Which is the best function to count the running time an algorithm?

Sep 17th, 2007

So anyway i fixed that not showing time problem - eclipse was just stupid and needed a restart. But can you tell me how can i get my program to work like that that it only works for a minutw? How and where do i have to write the while statent for it to do son?
So here is a littlebit changed version of the code

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
//rekursiivne algoritm
 
public class Fibo {
 
	//Fibonacci rekursiivse algoritmi põhiosa
	public static long fib(int n){
		if (n <= 2) return 1;//kui arv on väiksem kui kaks, siis tagastatakse "1"
	    else return fib(n-1) + fib(n-2);
	}
 
	public static void main(String[] args) {
			long start=System.nanoTime();
			start = start/10000000L;
			System.out.println("System time is: " +start);
			int N = Integer.parseInt(args[0]);//sisestus
			for(int i=2; i<=N;i++){//tsükkel, mida täidetakse, kuni nõudmised on rahuldatud
				System.out.println(i + ": " + fib(i));//väljatrükk
				//System.out.println(System.nanoTime());
			}
			long end=System.nanoTime();
			end = end/10000000L;
			long kulus=end-start;
			System.out.println("Elapsed time: "+kulus);
		}
}
//rekursiivne algoritm

public class Fibo {

	//Fibonacci rekursiivse algoritmi põhiosa
	public static long fib(int n){
		if (n <= 2) return 1;//kui arv on väiksem kui kaks, siis tagastatakse "1"
	    else return fib(n-1) + fib(n-2);
	}

	public static void main(String[] args) {
			long start=System.nanoTime();
			start = start/10000000L;
			System.out.println("System time is: " +start);
			int N = Integer.parseInt(args[0]);//sisestus
			for(int i=2; i<=N;i++){//tsükkel, mida täidetakse, kuni nõudmised on rahuldatud
				System.out.println(i + ": " + fib(i));//väljatrükk
				//System.out.println(System.nanoTime());
			}
			long end=System.nanoTime();
			end = end/10000000L;
			long kulus=end-start;
			System.out.println("Elapsed time: "+kulus);
		}
}