Re: timing functions and chunks of code in *nix?
- From: "qubit" <lauraeaves@xxxxxxxxx>
- To: <programmingblind@xxxxxxxxxxxxx>
- Date: Tue, 8 Feb 2011 11:51:00 -0600
Hi Ty and all -- This solution looks like your answer, and my comment may
not help at all, but consider it a resource. Have you profiled your program?
Building your program for profiling and running it will produce a bunch of
diagnostics giving the percentage of time spent in each function. This
can be helpful in tuning, obviously, but you do have to compile and link the
files for profiling -- I believe it was the -p flag.
See the prof and gprof commands. I used to do this all the time when I was
working, but it has been years so I am rusty.
HTH and happy hacking.
--le
----- Original Message -----
From: "Delaunay Christophe" <christophe.delaunay@xxxxxxxxxxxxxxx>
To: <programmingblind@xxxxxxxxxxxxx>
Sent: Tuesday, February 08, 2011 11:02 AM
Subject: RE: timing functions and chunks of code in *nix?
Hi Tyler,
According to the pieces of code you put in this message, I'm assuming you
are programming in a C-like language: C or C++, it does not matter, or just
little. Am I right?
So, here we go. The lines of C code are extracted from a library I made to
do this, but for logging purposes. The time measurement function I'm using
is a low-precision one, measuring time at a millisecond roundtrip or so.
On top of the logger module, I need the following line:
#include <sys/time.h>
This header contains the "timeval" data structure definition and the
"gettimeofday()" system call definition I'm using then.
Then, I need two data structures of type "timeval".
struct timeval prev, now; /* time of day with low precision, (expressed in
s+µs but rounded to ms) */
int val; /* used to compute a number of milliseconds */
In linux, your instruction "prev=gettime()" reads as:
gettimeofday(&prev, NULL);
then, you would have
myfunction();
as you did in your code.
Then,
gettimeofday(&now, NULL);
val = (now.tv_sec-prev.tv_sec)*1000 /* whole seconds if any multiplied by
1000 to get ms */
+ (int)((now.tv_usec-prev.tv_usec)/1000); /* number of µs from which I
compute integer division by 1000 to get ms */
and finally
printf("It took you %d milliseconds",val);
Apart from syntax errors I did not check since my linux box is off right
now.
For more info, please have a look to
man gettimeofday
HTH. Have a nice day. Chris D
-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Littlefield,
Tyler
Sent: mardi 8 février 2011 16:57
To: programmingblind@xxxxxxxxxxxxx
Subject: timing functions and chunks of code in *nix?
Hello all,
I know windows exposes high-resolution timers to do this sorta thing,
but I'm curious how I could do the same in Linux? Is there something
that will give me timing in ms? so:
prev = gettime();
myfunc();
now = gettime();
printf("you spent %d ms.\n", prev-now);
--
Thanks,
Ty
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