GCC time.h problem.

[Jaideep]

Hello!
I am new to GCC.I've abt 4-5 yrs of experience in windows
'C' programming.I find GCC much slower than turbo or microsoft
compilers.Anywa y I wrote this small piece of code to calculate process
time .The code works fine in windows compilers but gives erratic output
in GCC.What could be the problem?

code-->
....
#include <time.h>
.....
void main() {

clock_t start, end;

start = clock();
//process();

end = clock();
printf("The time was: %f\n", (end - start) / CLK_TCK);
}
Is there any other way of doing the same?

[Tim Prince]

Jaideep wrote:

Anyway I wrote this small piece of code to calculate process
time .The code works fine in windows compilers but gives erratic output
in GCC.What could be the problem?

code-->
...
#include <time.h>
....
void main() {

clock_t start, end;

start = clock();
//process();

end = clock();
printf("The time was: %f\n", (end - start) / CLK_TCK);
}
Is there any other way of doing the same?

c.l.c deals with standard C. Did you try a standard C version of this?
e.g. replace CLK_TCK by (double)CLOCKS_ PER_SEC
What makes you so sure that all "windows compilers" will work the same
with non-standard code?

[Eric Sosman]

Jaideep wrote:

Hello!
I am new to GCC.I've abt 4-5 yrs of experience in windows
'C' programming.I find GCC much slower than turbo or microsoft
compilers.Anywa y I wrote this small piece of code to calculate process
time .The code works fine in windows compilers but gives erratic output
in GCC.What could be the problem?

code-->
...
#include <time.h>
....
void main() {

clock_t start, end;

start = clock();
//process();

end = clock();
printf("The time was: %f\n", (end - start) / CLK_TCK);
}
Is there any other way of doing the same?

Possible reasons for "erratic output" (you ought to
have explained what you meant by that):

- You called the printf() function but failed to
#include <stdio.h>. Your program therefore has
undefined behavior.

- You declared the main() function as `void' instead
of `int'. Your program therefore has undefined
behavior.

- You used "%f" to print the result, but "%f" requires
a corresponding `double' value. You do not know the
type of the expression `(end - start) / CLK_TICK'
because each implementation gets to make its own
choice, so on an implementation where this expression
produces something other than a `double' your program
exhibits undefined behavior.

- On an implementation where `clock_t' and `CLK_TICK'
happen to be integers, you will compute a zero duration
for any interval of less than one second.

If you'll pardon my saying so, your "abt 4-5 yrs experience"
doesn't seem to have taught you much about C. Perhaps you've
been using some kind of C-ish dialect rather than C itself,
and have picked up a lot of misinformation and bad habits.

--
Eric Sosman
es*****@acm-dot-org.invalid

[Vladimir S. Oka]

Jaideep wrote:

Hello!
I am new to GCC.I've abt 4-5 yrs of experience in windows
'C' programming.I find GCC much slower than turbo or microsoft
I love the quotes in 'C'. LoL
compilers.Anywa y I wrote this small piece of code to calculate process
time .The code works fine in windows compilers but gives erratic output
in GCC.What could be the problem?

code-->
Not really, as it won't compile cut'n'pasted...
...
#include <time.h>
....
void main() {
This is your problem. After doing this, it's no longer C, and you may
observe weird stuff. Function `main` has to return an `int`.

clock_t start, end;

start = clock();
//process();

end = clock();
printf("The time was: %f\n", (end - start) / CLK_TCK);

Standard C does not mention CLK_TCK. Also, you don't include stdio.h,
so `printf` is unknown. And then, `clock_t` is integer type, and %f is
hardly the correct way of printing it.

[David Paleino]

Vladimir S. Oka ha scritto:

...

... Also, you don't include stdio.h,
so `printf` is unknown. ...

Well, just a point of note. We can't say "you don't include stdio.h", as
he makes a code ellipsis (see those dots around the `#include <time.h>'
line), so we don't actually know what he is including or not, or what
code is there between that inclusion and the `void main()' (which is
incorrect, as you already said).

David

--
Linux Registered User #334216
Get FireFox! >> http://www.spreadfirefox.com/?q=affiliates&id=48183&t=1
Staff >> http://www.debianizzati.org <<

[Jaideep]

Hi!
Of course I included stdio.h and other libraries.The code given is
not full.I've just included lines which I think might be
erronous.Regard ing int main if I remove this clock thing program just
works fine.Also tried converting everything to float but still it
gives arbritrary values.Here is my full program which calculates no
series like 2 3 4 2 1 3 1 4 (2 nos between two 2's 3 betweeen two 3's
etc.

/*Number series calculation */

#include <stdio.h>
#include <stdlib.h>

#include <time.h>
#define n 8
char pi[n+1];

void check (void);

int main( void )
{
int r, s, temp;
register int i,j;
clock_t start, end;
float p;

for (i=0; i <= n; i++) pi[i] = i;

start = clock();

i = 1;

while (i)
{
//for (i=1; i <= n; i++) printf( " %2d", pi[i] );
//printf( "\n" );
check();

i = n-1;
while (pi[i] > pi[i+1]) i--;

j = n;
while (pi[i] > pi[j]) j--;

temp = pi[i];
pi[i] = pi[j];
pi[j] = temp;

r = n;
s = i+1;
while (r > s)
{
temp = pi[r];
pi[r] = pi[s];
pi[s] = temp;
r--; s++;
}
}
end = clock();
p=(double) (end - start) / CLK_TCK;

printf("The time was: %f\n", p);
//getch();
return 0;
}

void check()
{
int i[3*n],l,q=0,s=0;
register int j;
for(j=0;j<(3*n) ;j++) i[j]=0;
for(j=0;j<(2*n) ;j++)
{
++q;
while(i[j]!=0) j++;
l=pi[q];
i[j]=l;
if(i[(j+1+l)] != 0) break;
i[(j+1+l)]=l;
if((j+1+l) >((2*n)-1)) break;
s=s+1;
}
if(s==n)
{
for(j=0;j<2*n;j ++) printf("%2d ", i[j]);
printf("\n");
//getch();
}
}

[Jaideep]

Hi!
Sorry I used int main(void) in program but wrote void main()
above.Program when run prints fixed process time no matter whatever
time it has taken.

[Vladimir S. Oka]

David Paleino wrote:

Vladimir S. Oka ha scritto:

...

... Also, you don't include stdio.h,
so `printf` is unknown. ...

Well, just a point of note. We can't say "you don't include stdio.h", as
he makes a code ellipsis (see those dots around the `#include <time.h>'
line), so we don't actually know what he is including or not, or what
code is there between that inclusion and the `void main()' (which is
incorrect, as you already said).

True, but since he went to the bother of including <time.h>, presumably
to justify using `clock()`, he should have done the same for
`printf()`. In any case, a minimal compilable example is what's needed,
especially in OPs.

[Vladimir S. Oka]

Jaideep wrote:

Hi!
Please quote what and who you're replying to (and don't top-post while
you're at it). See http://cfaj.freeshell.org/google/ for advice.
Of course I included stdio.h and other libraries.The code given is
not full.I've just included lines which I think might be
erronous.
You should have tried first and made sure that the snippet you posted is
erroneous. Also, if it's not compilable, many people here won't bother
look, as they expect to cut'n'paste and see for themselves.
Regarding int main if I remove this clock thing program just
works fine.Also tried converting everything to float but still it
gives arbritrary values.Here is my full program which calculates no
series like 2 3 4 2 1 3 1 4 (2 nos between two 2's 3 betweeen two 3's
etc.
I haven't looked whether code below really does what you claim it does,
but now it does compile cleanly. It also gives time of 100 consistently
on my SUSE Linux 10.0 box, so I don't know what you mean by "erratic"
in your OP.

[code not snipped for the benefit of whoever wants a look]
/*Number series calculation */

#include <stdio.h>
#include <stdlib.h>

#include <time.h>
#define n 8
char pi[n+1];

void check (void);

int main( void )
{
int r, s, temp;
register int i,j;
clock_t start, end;
float p;

for (i=0; i <= n; i++) pi[i] = i;

start = clock();

i = 1;

while (i)
{
//for (i=1; i <= n; i++) printf( " %2d", pi[i] );
//printf( "\n" );
check();

i = n-1;
while (pi[i] > pi[i+1]) i--;

j = n;
while (pi[i] > pi[j]) j--;

temp = pi[i];
pi[i] = pi[j];
pi[j] = temp;

r = n;
s = i+1;
while (r > s)
{
temp = pi[r];
pi[r] = pi[s];
pi[s] = temp;
r--; s++;
}
}
end = clock();
p=(double) (end - start) / CLK_TCK;

printf("The time was: %f\n", p);
//getch();
return 0;
}

void check()
{
int i[3*n],l,q=0,s=0;
register int j;
for(j=0;j<(3*n) ;j++) i[j]=0;
for(j=0;j<(2*n) ;j++)
{
++q;
while(i[j]!=0) j++;
l=pi[q];
i[j]=l;
if(i[(j+1+l)] != 0) break;
i[(j+1+l)]=l;
if((j+1+l) >((2*n)-1)) break;
s=s+1;
}
if(s==n)
{
for(j=0;j<2*n;j ++) printf("%2d ", i[j]);
printf("\n");
//getch();
}
}

--
BR, Vladimir

For perfect happiness, remember two things:
(1) Be content with what you've got.
(2) Be sure you've got plenty.

[Vladimir S. Oka]

Jaideep wrote:

Hi!
Sorry I used int main(void) in program but wrote void main()
above.Program when run prints fixed process time no matter whatever
time it has taken.

Even worse. it means you didn't even cut'n'paste into the post, but
re-typed. How then will we know whether your problem is in re-typing or
original code?

Again, quote, and generally follow the advice here:

http://cfaj.freeshell.org/google/

--
BR, Vladimir

It's not an optical illusion, it just looks like one.
-- Phil White