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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 do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
Idrissa Reply
im all ears I need to learn
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what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
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a perfect square v²+2v+_
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algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
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J, combine like terms 7x-4y
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how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris 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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I'm interested in nanotube
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Ramkumar Reply
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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
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele 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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