Valarray Vs. Array Matrix-calculation Performance

Demonstrates the usage of valarray and measures the performance of some arithmetic operations on matriced to be compared with the same operations performed with ordinary arrays. 


#include 
#include 
#include 
#include 
#include 
using namespace std;

void rndm(float& a);
void zerocheck(float& a);
double duration(vector::iterator start, vector::iterator stop);

int main()
{
  int i(0);
  int p(0);
  float k(5.3235),l(9.212);
  int size(4000000);

  vector vstart;
  vector vstop;
  vector::iterator istartclock;
  vector::iterator istopclock;
  vector vfloat(size);
  vector::iterator ifloat;
  valarray valfloat(size);

  cout << "Filling float array with " << size << " random elements" << endl;
  cout << "(each element needs " << sizeof(float) << " bytes of memory, so " \
       << "we need to make use of " << size*sizeof(float)/1000000<< "MBytes.)"<< endl;

  // ======================= ORDINARY OPERATIONS =======================
  // fill array

  vstart.push_back(clock());
  //  vfloat.resize(size);
  ifloat=vfloat.begin();
  for_each(vfloat.begin(),vfloat.end(),rndm);
  vstop.push_back(clock());

  cout << "****** Phase 1: Math. operations on ordinary array" << endl;  

  // Add k to each element
  cout << "*** Adding " << k << " to each element " ;
  cout << "(10th element was: " << *(ifloat+10) ;
  vstart.push_back(clock());
  for (i=0; i::iterator start, 
	      vector::iterator stop
	      )
{
  return difftime(*stop,*start) ;
}