change clock's precision

[Robert]

Hello all,

I use clock() to measure the time cost in my program.
But the t_clock always be the multiply of 10, for example 10, 20, 30,
40,...
And I want to get the precision of 1, such as 11, 12, 13, 14...
How can I change the t_clock's precision?

Code list below:
//-----------------
#include <cstdio>
#include <fstream.h>
#include <ctime>

void main() {
int x;
clock_t t_click,t_start;

t_start = clock();
for (x=0;x<60;x++) {
printf("%d\n",x);
}

t_click = clock() - t_start;
printf("Time Elapsed %d\n",t_click);

}
//-------------------
BTW, I use VC6.0. The environment is P3 600MHz and WinXP.

Any suggestions will be appreciated!

Best regards,
Davy

[Karl Heinz Buchegger]

Robert wrote:

Hello all,

I use clock() to measure the time cost in my program.
But the t_clock always be the multiply of 10, for example 10, 20, 30,
40,...
And I want to get the precision of 1, such as 11, 12, 13, 14...
How can I change the t_clock's precision?

You can't.
The 'precision' is given to you and there is no way to change
that. That may eg. be because the hardware doesn't support a
finer granularity.

--
Karl Heinz Buchegger
kb******@gascad.at

[Walter Roberson]

In article <11*********************@g49g2000cwa.googlegroups. com>,
Robert <zh*******@gmail.com> wrote:

I use clock() to measure the time cost in my program.
But the t_clock always be the multiply of 10, for example 10, 20, 30,
40,...
And I want to get the precision of 1, such as 11, 12, 13, 14...
How can I change the t_clock's precision?
There is no way to do that in standard C. Keep in mind that
clock_t is a count of CLOCKS_PER_SEC and not an absolute time,
so a value of 10 might mean 10 femtoseconds with the extra digit
reserved for the next board rev with the built-in 1 femtosecond
counter.

Code list below:
//-----------------
// comments are not allowed in C89.
#include <cstdio>
#include <fstream.h>
#include <ctime>
Those are not standard C headers. If you expect us to be able to
understand your program in comp.lang.c, you will have to provide the
expansion of the headers.

void main() {
In standards-compliant C code, main() must return an int.

Also, if you are not declaring parameters for main, it is
better practice to prototype it as main(void)
int x;
clock_t t_click,t_start;

t_start = clock();
for (x=0;x<60;x++) {
printf("%d\n",x);
}

t_click = clock() - t_start;
printf("Time Elapsed %d\n",t_click);
You did not divide by CLOCKS_PER_SEC so printing out the number
of ticks gives us no idea how long the program took.
}
In C89, if you do not return a value from main, the exit status
of the program is undefined.
//-------------------
BTW, I use VC6.0. The environment is P3 600MHz and WinXP. Any suggestions will be appreciated!

Any higher precision timing would be implementation specific,
and is thus not a suitable topic for comp.lang.c .
This topic is, by the way, disposed of in the comp.lang.c FAQ...
--
Programming is what happens while you're busy making other plans.

[Ali Çehreli]

"Robert" <zh*******@gmail.com> wrote in message
news:11*********************@g49g2000cwa.googlegro ups.com...

I use clock() to measure the time cost in my program.
But the t_clock always be the multiply of 10, for example 10, 20, 30,
40,...
And I want to get the precision of 1, such as 11, 12, 13, 14...
How can I change the t_clock's precision?
You cannot change the precision; you can only measure. Windows allocates
each thread a certain amount of time slice. Apparently the granularity of
that slice on your system is 10/CLOCKS_PER_SEC seconds.

Use a different timing function.

[It is completely off-topic on this group, and my Windows programming skills
are very rusty, but you may start reading on GetTickCount and
QueryPerformanceCounter functions.]
Code list below:
//-----------------
#include <cstdio>
#include <fstream.h>
<fstream.h> is pre-standard; use <fstream> instead. (Though you don't use it
in the program.)
#include <ctime>

void main() {
'void main' is not standard; should be 'int main'
int x;
clock_t t_click,t_start;

t_start = clock();
for (x=0;x<60;x++) {
printf("%d\n",x);
}

t_click = clock() - t_start;
printf("Time Elapsed %d\n",t_click);
This is one example that demonstrates the superiority of C++'s operator<<
overloading over printf. Since we don't know the actual type of clock_t, we
cannot know what format identifier to use with printf (%d didn't match
clock_t on my system).

This works:

cout << "Time Elapsed: " << t_click << '\n';
}
//-------------------
BTW, I use VC6.0.

In that case, in addition to using 'int main', you will have to explicitly
add a return statement at the end of your main function:

return 0;

That statement is not necessary and most other compilers get that right; but
VC++60 needs you to type it. In other words, even though the following is a
valid C++ program, VC++60 will need you to add a return statement.

int main()
{}

Ali

[Mark B]

"Robert" <zh*******@gmail.com> wrote in message
news:11*********************@g49g2000cwa.googlegro ups.com...

Hello all,

I use clock() to measure the time cost in my program.
But the t_clock always be the multiply of 10, for example 10, 20, 30,
40,...
And I want to get the precision of 1, such as 11, 12, 13, 14...
How can I change the t_clock's precision?

divide it by 10 ;)

[RamOn]

Hello,

Under Windows, maybe you can get advantage of using timeGetTime() /
timeBeginPeriod() / timeEndPeriod() instead of clock()

Hope this helps

RamOn
In article <11*********************@g49g2000cwa.googlegroups. com>,
zh*******@gmail.com says...

Hello all,

I use clock() to measure the time cost in my program.
But the t_clock always be the multiply of 10, for example 10, 20, 30,
40,...
And I want to get the precision of 1, such as 11, 12, 13, 14...
How can I change the t_clock's precision?

Code list below:
//-----------------
#include <cstdio>
#include <fstream.h>
#include <ctime>

void main() {
int x;
clock_t t_click,t_start;

t_start = clock();
for (x=0;x<60;x++) {
printf("%d\n",x);
}

t_click = clock() - t_start;
printf("Time Elapsed %d\n",t_click);

}
//-------------------
BTW, I use VC6.0. The environment is P3 600MHz and WinXP.

Any suggestions will be appreciated!

Best regards,
Davy