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For FORTRAN programs, a library timing function found on many machines is called etime , which takes a two-element REAL*4 array as an argument and fills the slots with the user CPU time and system CPU time, respectively. The value returned by the function is the sum of the two. Here’s how etime is often used:

real*4 tarray(2), etime real*4 start, finishstart = etime(tarray)finish = etime(tarray)write (*,*) ’CPU time: ’, finish - start

Not every vendor supplies an etime function; in fact, one doesn’t provide a timing routine for FORTRAN at all. Try it first. If it shows up as an undefined symbol when the program is linked, you can use the following C routine. It provides the same functionality as etime :

#include<sys/times.h>#define TICKS 100.float etime (parts) struct {float user; float system;} *parts; {struct tms local; times (&local); parts->user= (float) local.tms_utime/TICKS; parts->system = (float) local.tms_stime/TICKS; return (parts->user + parts->system); }

There are a couple of things you might have to tweak to make it work. First of all, linking C routines with FORTRAN routines on your computer may require you to add an underscore (_) after the function name. This changes the entry to float etime_ (parts) . Furthermore, you might have to adjust the TICKS parameter. We assumed that the system clock had a resolution of 1/100 of a second (true for the Hewlett-Packard machines that this version of etime was written for). 1/60 is very common. On an RS-6000 the number would be 1000. You may find the value in a file named /usr/include/sys/param.h on your machine, or you can determine it empirically.

A C routine for retrieving the wall time using calling gettimeofday is shown below. It is suitable for use with either C or FORTRAN programs as it uses call-by-value parameter passing:

#include<stdio.h>#include<stdlib.h>#include<sys/time.h>void hpcwall(double *retval){ static long zsec = 0;static long zusec = 0; double esec;struct timeval tp; struct timezone tzp;gettimeofday(&tp,&tzp);if ( zsec == 0 ) zsec = tp.tv_sec; if ( zusec == 0 ) zusec = tp.tv_usec;*retval = (tp.tv_sec - zsec) + (tp.tv_usec - zusec ) * 0.000001 ;}void hpcwall_(double *retval) { hpcwall(retval); } /* Other convention */

Given that you will often need both CPU and wall time, and you will be continu- ally computing the difference between successive calls to these routines, you may want to write a routine to return the elapsed wall and CPU time upon each call as follows:


Using timing information

You can get a lot information from the timing facilities on a UNIX machine. Not only can you tell how long it takes to perform a given job, but you can also get hints about whether the machine is operating efficiently, or whether there is some other problem that needs to be factored in, such as inadequate memory.

Once the program is running with all anomalies explained away, you can record the time as a baseline. If you are tuning, the baseline will be a reference with which you can tell how much (or little) tuning has improved things. If you are benchmarking, you can use the baseline to judge how much overall incremental performance a new machine will give you. But remember to watch the other figures — paging, CPU utilization, etc. These may differ from machine to machine for reasons unrelated to raw CPU performance. You want to be sure you are getting the full picture.

Questions & Answers

how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
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what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, High performance computing. OpenStax CNX. Aug 25, 2010 Download for free at http://cnx.org/content/col11136/1.5
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