Index

NAME

CPUclock - measures the CPU time in C++ programs

INCLUDE

include "CPUclock.h"

SYNTAX

 class CPUclock
 {
   bool   locked_clock;  // true: getInterval does not reset the time
   long   tunits;        // number of timing units per second for struct tms

 #ifndef WIN32
   tms       last;       // previous clock value
   tms       now;        // present clock value
   tms       diff;       // diff = now - last
 #else
   _timeb    last;       // previous clock value
   _timeb    now;        // present clock value
   _timeb    diff;       // diff = now - last
   clock_t   now_cpu;
   clock_t   last_cpu;
   clock_t   diff_cpu;        // time used by this process
 #endif

   void   swap();        // last = now
   void   subt();        // subtract: now - last, store in diff

   double convert2sec (clock_t tm)     // convert to seconds
     { return double(tm)/double(tunits); }

 public:
   CPUclock ();

   // the increase in time (seconds) since last call to  getInterval
   // or to  initTime ();
   double getInterval  ();  // returns user time + system time
   double getIntervalU ();  // returns user time only

   void   initTime ()  { getInterval(); }

   double getTime ();  // return absolute user time, Win32 returning "now_cpu"

   void   lock () { locked_clock = true; }
   void unlock () { locked_clock = false; }
   bool locked () const { return locked_clock; }
 };

KEYWORDS

CPU time, clock

DESCRIPTION

One  can  get the user time in absolute seconds, or the length of
intervals can be measured (in seconds).

getTime - returns absolute user time in seconds

initTime - start measuring the length of an  interval  (typically
called  prior  to the computational job to be measured). In fact,
initTime is just a call to getInterval -  the  function  was  for
making programs easier to read.

getInterval - returns the length of the user+system time interval
(in seconds) between the present call to getInterval and the last
call to initTime or to getInterval.

getIntervalU  -  as  getInterval,  but  only  the  user  time  is
returned.

EXAMPLE

| #include <CPUclock.h>

class MySolver
{
  ...
  CPUclock cpu_clock;
  ...
};

void MySolver::solveProblem()
{
  cpu_clock.getInterval(); // initialize
  // call various solve functionality
  real cpu_time = cpu_clock.getInterval() // CPU time since  last
call
  s_o << "solveProblem used " << cpu_time " seconds0;
}

REMARKS

Some utility classes in Diffpack, like  FEM  and  LinEqAdm,  have
built-in CPUclock data members. Simulators derived from class FEM
inherit the real variable cpu_time_makeSystem, which contains the
CPU time consumption in the last call to makeSystem.  If a solver
employs a lineq handle to a LinEqAdm object  for  solving  linear
systems,  the call lineq->getCPUtime4solve() returns the CPU time
required by the execution of the linear  system  solution  proce­
dure, i.e., the last lineq->solve() call. The CPU time for assem­
bly and solve processes are automatically reported in  the  case­
name.dp file.

SEE ALSO

"time.h, sys/times.h

DEVELOPED BY

SINTEF Applied Mathematics, Oslo, Norway, and University of Oslo,
Dept. of Mathematics, Norway

AUTHOR

Hans Petter Langtangen, SINTEF/UiO