Programming Forums > Application Development > C

Pacer · May 29th, 2006, 11:01 AM

Hello,all.Following is my homework,which is the better(faster and so on).
Thanks.
A.

#include <stdio.h>

int main()
{
        int i,j;
        for(i=0;i<26;i++)
        {
                for(j=0;j<26-i;j++)
                        printf(" ");
                for(j=0;j<i;j++)
                        printf("%c",j+65);
                for(j=i;j>=0;j--)
                        printf("%c",j+65);
                printf("\n");
        }
        return 0;
}

B.

(Toggle Plain Text)

#include <stdio.h>
int main(void)
{
        int i,j;
        int space;
        
        for(i=1;i<=6;i++)
        {
                int c=65;
                space=6-i;

                for(j=1;j<=2*i-1;j++)
                {
                        while(space>0)
                        {
                                printf(" ");
                                space--;
                        }

                        if(j==1)
                                printf("%c",c);
                        else if(j>1&&j<=i)
                        {
                                ++c;
                                printf("%c",c);
                        }
                        else
                        {
                                --c;
                                printf("%c",c);
                        }
                        
                }
                printf("\n");
        }
}

DaWei · May 29th, 2006, 11:12 AM

Why don't you use your debugger or a pencil and paper and traipse around your code?

Adak · Jun 1st, 2006, 4:29 AM

The FIRST thing to remember in programming, is it's not an ultimate sprint. There will always be faster cpu's, etc., to move your program along. Speed HAS to take a back seat.

Your looking for:

*Accuracy,
*Clarity of the code,
*well-chosen algorithms,
*good interface for the end user's,

Then, speed!

If you're coding up something to intercept a speeding missile in mid-air, then speed gets moved up, considerably, but in general, the above characteristics of a good program, hold up well.

Your first choice code example is better for speed. If statements can cause a lot more work because of the way they're handled in the cache memory.

Adak

DaWei · Jun 1st, 2006, 6:06 AM

I think you're thinking of branching instructions at the machine code level. The cpu neither knows nor cares about "if" statements. Branching statements are generated at any point in the code that requires it, whether it's generated by an "if" or by some loop or switch construct. The OP should concern himself, rightly, with efficiently written code, and not run from "if" statements. Optimization is the province of those who know what they're doing in detail (and write good compilers).

Serinth · Jun 1st, 2006, 8:26 AM

you can also use the "time" command in linux. type "man time" to find out more.

java_roshan · Jun 1st, 2006, 11:46 AM

Ultimately, all these code, irrespective of being written in any language, will be compiled into machine code. So, the machine code that a CPU will understand and execute faster; will be faster. Am I right?

Possibly, the OP should understand, how each of his code, A and B, would take up CPU time, and then identify which of his code is better in terms of speed!

Serinth · Jun 1st, 2006, 12:33 PM

One of my university courses teaches some stuff on timing, efficiency and whatnot. They also refer to the Big O or O(n) and stuff like that. I've still yet to learn it

NSchnarr · Jun 1st, 2006, 2:14 PM

@Serinth your referring to Big O Notation, I learned it it my first year java course at university. We laerned all about analysing algorithms, determining which ones ran more efficiently than others and why. O(n), O(logn), O(nlogn), O(n^2), O(n^3) is the notation for it. Not exactly fun stuff to pour through an algorithms and provide proofs as to why it runs O(n^2) or w/e, but it was interesting.

Serinth · Jun 2nd, 2006, 12:56 AM

NSchnarr, usually i just read how many loops or recursions it has to go through lol :\ I don't really go to class >:3

NSchnarr · Jun 2nd, 2006, 11:04 AM

Haha, yea that works quite well to just give you an idea of how the program runs. IE, two nested for loops both based off of n runs O(N^2), easy enough. My class required me to mathematically prove why, not so fun. End up with the same answer, but much more work.

May 29th, 2006, 11:01 AM	#1
Pacer Newbie Join Date: May 2006 Posts: 4 Rep Power: 0	which is better? Hello,all.Following is my homework,which is the better(faster and so on). Thanks. A. (Toggle Plain Text) #include <stdio.h> int main() { int i,j; for(i=0;i<26;i++) { for(j=0;j<26-i;j++) printf(" "); for(j=0;j<i;j++) printf("%c",j+65); for(j=i;j>=0;j--) printf("%c",j+65); printf("\n"); } return 0; } #include <stdio.h> int main() { int i,j; for(i=0;i<26;i++) { for(j=0;j<26-i;j++) printf(" "); for(j=0;j<i;j++) printf("%c",j+65); for(j=i;j>=0;j--) printf("%c",j+65); printf("\n"); } return 0; } B. (Toggle Plain Text) #include <stdio.h> int main(void) { int i,j; int space; for(i=1;i<=6;i++) { int c=65; space=6-i; for(j=1;j<=2i-1;j++) { while(space>0) { printf(" "); space--; } if(j==1) printf("%c",c); else if(j>1&&j<=i) { ++c; printf("%c",c); } else { --c; printf("%c",c); } } printf("\n"); } } #include <stdio.h> int main(void) { int i,j; int space; for(i=1;i<=6;i++) { int c=65; space=6-i; for(j=1;j<=2i-1;j++) { while(space>0) { printf(" "); space--; } if(j==1) printf("%c",c); else if(j>1&&j<=i) { ++c; printf("%c",c); } else { --c; printf("%c",c); } } printf("\n"); } }

May 29th, 2006, 11:12 AM	#2
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Why don't you use your debugger or a pencil and paper and traipse around your code? __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jun 1st, 2006, 6:06 AM	#4
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	I think you're thinking of branching instructions at the machine code level. The cpu neither knows nor cares about "if" statements. Branching statements are generated at any point in the code that requires it, whether it's generated by an "if" or by some loop or switch construct. The OP should concern himself, rightly, with efficiently written code, and not run from "if" statements. Optimization is the province of those who know what they're doing in detail (and write good compilers). __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jun 1st, 2006, 8:26 AM	#5
Serinth Programmer Join Date: Sep 2005 Posts: 50 Rep Power: 4	you can also use the "time" command in linux. type "man time" to find out more. __________________ A girl talked to me once. http://www.latestanime.com

Jun 1st, 2006, 11:46 AM	#6
java_roshan Professional Programmer Join Date: Mar 2005 Location: Student of University of Mumbai, Maharashtra State, India Posts: 344 Rep Power: 4	Ultimately, all these code, irrespective of being written in any language, will be compiled into machine code. So, the machine code that a CPU will understand and execute faster; will be faster. Am I right? Possibly, the OP should understand, how each of his code, A and B, would take up CPU time, and then identify which of his code is better in terms of speed! __________________ Visit: http://www.somaiya.edu

Jun 1st, 2006, 4:29 AM	#3
Adak Hobby Coder Join Date: May 2006 Posts: 58 Rep Power: 0	The FIRST thing to remember in programming, is it's not an ultimate sprint. There will always be faster cpu's, etc., to move your program along. Speed HAS to take a back seat. Your looking for: Accuracy, Clarity of the code, well-chosen algorithms, good interface for the end user's, Then, speed! If you're coding up something to intercept a speeding missile in mid-air, then speed gets moved up, considerably, but in general, the above characteristics of a good program, hold up well. Your first choice code example is better for speed. If statements can cause a lot more work because of the way they're handled in the cache memory. Adak

Jun 1st, 2006, 12:33 PM	#7
Serinth Programmer Join Date: Sep 2005 Posts: 50 Rep Power: 4	One of my university courses teaches some stuff on timing, efficiency and whatnot. They also refer to the Big O or O(n) and stuff like that. I've still yet to learn it __________________ A girl talked to me once. http://www.latestanime.com

Jun 1st, 2006, 2:14 PM	#8
NSchnarr Newbie Join Date: May 2006 Posts: 28 Rep Power: 0	@Serinth your referring to Big O Notation, I learned it it my first year java course at university. We laerned all about analysing algorithms, determining which ones ran more efficiently than others and why. O(n), O(logn), O(nlogn), O(n^2), O(n^3) is the notation for it. Not exactly fun stuff to pour through an algorithms and provide proofs as to why it runs O(n^2) or w/e, but it was interesting.

Jun 2nd, 2006, 12:56 AM	#9
Serinth Programmer Join Date: Sep 2005 Posts: 50 Rep Power: 4	NSchnarr, usually i just read how many loops or recursions it has to go through lol :\ I don't really go to class >:3 __________________ A girl talked to me once. http://www.latestanime.com

Jun 2nd, 2006, 11:04 AM	#10
NSchnarr Newbie Join Date: May 2006 Posts: 28 Rep Power: 0	Haha, yea that works quite well to just give you an idea of how the program runs. IE, two nested for loops both based off of n runs O(N^2), easy enough. My class required me to mathematically prove why, not so fun. End up with the same answer, but much more work.

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Programming Forums > Application Development > C

which is better?