Why is valarray so slow?

Question

I am trying to use valarray since it is much like MATLAB while operating vector and matrices. I first did some performance check and found that valarray cannot achieve the p

Answer 1

Hmm..I tested Blitz++ and it's same as valarray... And moreover, the Blitz++ [] operator is very slow.

#include 
#include 

#ifdef WIN32
#include "windows.h"
LARGE_INTEGER sys_freq;
#endif

#ifdef LINUX

#endif

using namespace std;
SYSTEMTIME stime;

__forceinline double gettime_hp();
double gettime_hp()
{
    #ifdef WIN32
        LARGE_INTEGER tick;
        extern LARGE_INTEGER sys_freq;
        QueryPerformanceCounter(&tick);
        return (double)tick.QuadPart * 1000.0 / sys_freq.QuadPart;
    #endif

    #ifdef LINUX
        struct timespec timestamp;

        clock_gettime(CLOCK_REALTIME, ×tamp);
        return timestamp.tv_sec * 1000.0 + timestamp.tv_nsec * 1.0e-6;
    #endif
}
BZ_USING_NAMESPACE(blitz)

int main()
{
    int N = 5*1024*1024;

    // Create three-dimensional arrays of double
    Array a(N), b(N), c(N);

    int i, j;

    #ifdef WIN32
        QueryPerformanceFrequency(&sys_freq);
    #endif

    for (j=0 ; j<8 ; ++j)
    {
        for (i=0 ; i