使用模板表达式的向量类
// numeric.h
#ifndef _NUMERIC_H_
#define _NUMERIC_H_
#include <memory> // memcpy
#include <iostream> // std::
using namespace std;
namespace numeric {
#define max(a,b) (((a) > (b)) ? (a) : (b))
#define min(a,b) (((a) > (b)) ? (b) : (a))
template <class T>
class expr_add
{
public:
static inline T apply(const T& a, const T& b)
{
return a + b;
}
};
template <class T>
class expr_sub
{
public:
static inline T apply(const T& a, const T& b)
{
return a - b;
}
};
template <class T>
class expr_mul
{
public:
static inline T apply(const T& a, const T& b)
{
return a * b;
}
};
template <class T>
class expr_div
{
public:
static inline T apply(const T& a, const T& b)
{
return a / b;
}
};
template <class A, class B, class Op>
class tpl_expr
{
const A& a_;
const B& b_;
public:
tpl_expr(const A& a, const B& b) : a_(a), b_(b) { }
inline double operator[](size_t i) const
{
return Op::apply(a_[i], b_[i]);
}
};
template <class B, class Op>
class tpl_expr <double, B, Op>
{
const double& a_;
const B& b_;
public:
tpl_expr(const double& a, const B& b) : a_(a), b_(b) { }
inline double operator[](size_t i) const
{
return Op::apply(a_, b_[i]);
}
};
template <class B, class Op>
class tpl_expr <int, B, Op>
{
const int& a_;
const B& b_;
public:
tpl_expr(const int& a, const B& b) : a_(a), b_(b) { }
inline double operator[](size_t i) const
{
return Op::apply(a_, b_[i]);
}
};
template <class A, class Op>
class tpl_expr <A, double, Op>
{
const A& a_;
const double& b_;
public:
tpl_expr(const A& a, const double& b) : a_(a), b_(b) { }
inline double operator[](size_t i) const
{
return Op::apply(a_[i], b_);
}
};
template <class A, class Op>
class tpl_expr <A, int, Op>
{
const A& a_;
const int& b_;
public:
tpl_expr(const A& a, const int& b) : a_(a), b_(b) { }
inline double operator[](size_t i) const
{
return Op::apply(a_[i], b_);
}
};
template <class A, class B>
tpl_expr<A, B, expr_add<double> > operator+(const A& a, const B& b)
{
return tpl_expr<A, B, expr_add<double> >(a, b);
}
template <class A, class B>
tpl_expr<A, B, expr_sub<double> > operator-(const A& a, const B& b)
{
return tpl_expr<A, B, expr_sub<double> >(a, b);
}
template <class A, class B>
tpl_expr<A, B, expr_mul<double> > operator*(const A& a, const B& b)
{
return tpl_expr<A, B, expr_mul<double> >(a, b);
}
template <class A, class B>
tpl_expr<A, B, expr_div<double> > operator/(const A& a, const B& b)
{
return tpl_expr<A, B, expr_div<double> >(a, b);
}
/////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////
class vector
{
protected:
size_t dim;
double *ets;
public:
// 由已知向量个数和向量元素数组来构造一个向量
vector(size_t n, const double* const pd)
: dim(n)
{
ets = new double[dim];
memcpy(ets, pd, dim*sizeof(double));
}
vector(size_t n = 0, double d = 0.0)
: dim(n)
{
ets = new double[dim];
for (size_t i=0; i<dim; ++i) {
ets[i] = d;
}
}
vector(const vector& v)
{
dim = v.dim;
ets = new double[dim];
memcpy(ets, v.ets, sizeof(double)*dim);
}
vector& operator=(const vector& v)
{
if (this != &v) { // 防止自己拷贝自己
if (dim != v.dim) {
exit(1);
}
memcpy(ets, v.ets, sizeof(double)*dim);
}
return *this;
}
~vector()
{
delete[] ets;
}
public:
inline double operator[](size_t i) const
{
return ets[i];
}
inline double& operator[](size_t i)
{
return ets[i];
}
public:
size_t get_dim() const
{
return dim;
}
double* get_ptr() const
{
return ets;
}
double sum_element() const
{
double tmp = 0;
for (size_t i=0; i<dim; ++i) {
tmp += ets[i];
}
return tmp;
}
double min_element() const
{
double tmp = ets[0];
for (size_t i=0; i<dim; ++i) {
if (tmp > ets[i]) {
tmp = ets[i];
}
}
return tmp;
}
double max_element() const
{
double tmp = ets[0];
for (size_t i=0; i<dim; ++i) {
if (tmp < ets[i]) {
tmp = ets[i];
}
}
return tmp;
}
public:
vector& operator+()
{
return *this;
}
vector& operator-()
{
for (size_t i=0; i<dim; ++i) {
ets[i] = -ets[i];
}
return *this;
}
public:
vector& operator+=(const vector& v)
{
for (size_t i=0; i<dim; ++i) {
ets[i] += v[i];
}
return *this;
}
vector& operator-=(const vector& v)
{
for (size_t i=0; i<dim; ++i) {
ets[i] -= v[i];
}
return *this;
}
vector& operator*=(const vector& v)
{
for (size_t i=0; i<dim; ++i) {
ets[i] *= v[i];
}
return *this;
}
vector& operator/=(const vector& v)
{
for (size_t i=0; i<dim; ++i) {
ets[i] /= v[i];
}
return *this;
}
vector& operator+=(const double& d)
{
for (size_t i=0; i<dim; ++i) {
ets[i] += d;
}
return *this;
}
vector& operator-=(const double& d)
{
for (size_t i=0; i<dim; ++i) {
ets[i] -= d;
}
return *this;
}
vector& operator*=(const double& d)
{
for (size_t i=0; i<dim; ++i) {
ets[i] *= d;
}
return *this;
}
vector& operator/=(const double& d)
{
double tmp = 1/d;
for (size_t i=0; i<dim; ++i) {
ets[i] *= tmp;
}
return *this;
}
public:
template <class A, class B, class Op>
vector& operator=(const tpl_expr<A, B, Op>& expr)
{
for (size_t i=0; i<dim; ++i) {
ets[i] = expr[i];
}
return *this;
}
template <class A, class B, class Op>
vector& operator+=(const tpl_expr<A, B, Op>& expr)
{
for (size_t i=0; i<dim; ++i) {
ets[i] += expr[i];
}
return *this;
}
template <class A, class B, class Op>
vector& operator-=(const tpl_expr<A, B, Op>& expr)
{
for (size_t i=0; i<dim; ++i) {
ets[i] -= expr[i];
}
return *this;
}
template <class A, class B, class Op>
vector& operator*=(const tpl_expr<A, B, Op>& expr)
{
for (size_t i=0; i<dim; ++i) {
ets[i] *= expr[i];
}
return *this;
}
template <class A, class B, class Op>
vector& operator/=(const tpl_expr<A, B, Op>& expr)
{
for (size_t i=0; i<dim; ++i) {
ets[i] /= expr[i];
}
return *this;
}
};
};
#endif // _NUMERIC_H_
// test.cpp
#include <ctime>
#include <iostream>
#include <valarray>
using namespace std;
#include "numeric.h"
using namespace numeric;
void main()
{
int m = 10000, n=10000;
// vector x(m, 1), y(m, 2), z(m, 3);
valarray<double> x(1, m), y(2, m), z(3, m);
clock_t time;
time = clock();
for (size_t i=0; i<n; ++i) {
z = 0.5-(x - y)*1.0;
}
time = clock() - time;
cout << z[0] << endl;
cout << time/1000.0 << endl;
}
