我有三个类模板,它们全部使用相同的成员数据和相同方法的不同实例。
我想创建一个基类模板,并让这三个继承它:
#include <vector>
#include <memory>
template <typename Sde>
class EulerFdm
{
private:
std::shared_ptr<Sde> sde;
int NT;
public:
std::vector<double> x; // The mesh array
double k; // Mesh size
double dtSqrt;
public:
EulerFdm() = default;
EulerFdm(const std::shared_ptr<Sde>& stochasticEquation, int numSubdivisions)
: sde(stochasticEquation), NT(numSubdivisions)
{
NT = numSubdivisions;
k = sde->Expiry() / static_cast<double>(NT);
dtSqrt = std::sqrt(k);
x = std::vector<double>(NT + 1);
// Create the mesh array
x[0] = 0.0;
for (std::size_t n = 1; n < x.size(); ++n)
{
x[n] = x[n - 1] + k;
}
}
double advance(double xn, double tn, double dt, double normalVar, double normalVar2) const
{
return xn + sde->Drift(xn, tn) * dt + sde->Diffusion(xn, tn) * dtSqrt * normalVar;
}
};
template <typename Sde>
class EulerHeun
{
private:
std::shared_ptr<Sde> sde;
int NT;
public:
std::vector<double> x; // The mesh array
double k; // Mesh size
double dtSqrt;
public:
EulerHeun() = default;
EulerHeun(const std::shared_ptr<Sde>& stochasticEquation, int numSubdivisions)
: sde(stochasticEquation), NT(numSubdivisions)
{
NT = numSubdivisions;
k = sde->Expiry() / static_cast<double>(NT);
dtSqrt = std::sqrt(k);
x = std::vector<double>(NT + 1);
// Create the mesh array
x[0] = 0.0;
for (std::size_t n = 1; n < x.size(); ++n)
{
x[n] = x[n - 1] + k;
}
}
double advance(double xn, double tn, double dt, double normalVar, double normalVar2) const
{
auto a = sde->Drift(xn, tn);
auto b = sde->Diffusion(xn, tn);
auto suppValue = xn + a * dt + b * std::sqrt(dt) * normalVar;
return xn + 0.5 * (sde->Drift(suppValue, tn) + a) * dt
+ 0.5 * (sde->Diffusion(suppValue, tn) + b) * std::sqrt(dt) * normalVar;
}
};
template <typename Sde>
class FdmFRKI
{
private:
std::shared_ptr<Sde> sde;
int NT;
public:
std::vector<double> x; // The mesh array
double k; // Mesh size
double dtSqrt;
public:
FdmFRKI() = default;
FdmFRKI(const std::shared_ptr<Sde>& stochasticEquation, int numSubdivisions)
: sde(stochasticEquation), NT(numSubdivisions)
{
NT = numSubdivisions;
k = sde->Expiry() / static_cast<double>(NT);
dtSqrt = std::sqrt(k);
x = std::vector<double>(NT + 1);
// Create the mesh array
x[0] = 0.0;
for (std::size_t n = 1; n < x.size(); ++n)
{
x[n] = x[n - 1] + k;
}
}
double advance(double xn, double tn, double dt, double normalVar, double normalVar2) const
{
auto sqrk = std::sqrt(dt);
auto Wincr = sqrk * normalVar;
auto F1 = sde->Drift(xn, tn);
auto G1 = sde->Diffusion(xn, tn);
auto G2 = sde->Diffusion(xn + 0.5 * G1 * (Wincr - sqrk), tn);
return xn + (F1 * dt + G2 * Wincr + (G2 - G1) * sqrk);
}
};
我试图按如下方式构建基类FdmBase:
template<typename Sde>
class FdmBase
{
protected:
std::shared_ptr<Sde> sde;
int NT;
public:
std::vector<double> x;
double k;
double dtSqrt;
FdmBase() = default;
FdmBase(const std::shared_ptr<Sde>& stochasticEquation, int numSubdivision) : sde(stochasticEquation), NT(numSubdivisions)
{
NT = numSubdivisions;
k = sde->Expiry() / static_cast<double>(NT);
dtSqrt = std::sqrt(k);
x = std::vector<double>(NT + 1);
// Create the mesh array
x[0] = 0.0;
for (std::size_t n = 1; n < x.size(); ++n)
{
x[n] = x[n - 1] + k;
}
}
};
但是,当我删除派生类中的私有成员时,程序无法编译。
这就是我在main()方法中调用它的方式:
auto fdm = std::shared_ptr<EulerFdm<Sde1>>(new EulerFdm<Sde1>(sde,NT));
答案 0 :(得分:1)
模板继承中可能存在两个不同的问题,具体取决于您调整模板以考虑继承的精确程度。
第一个潜在的问题适用于所有类,包括非模板类:您只能使用基类构造函数并在mem-initializers中直接使用该类的成员。因此,您需要通过分配将sde
和NT
初始化移到构造函数主体中,或者让基类构造函数对其进行初始化。使用非模板基类,则一切都会好起来。
但是对于模板类,还有第二个问题related to the way in which name resolution is performed。这将导致在您的示例中找不到基本模板类的成员,并导致您描述的错误消息。可以通过使成员在派生类中显式可见来解决此问题,如以下示例所示:
template <typename T>
class B {
protected:
T a,b;
public:
B() : a(10)
{
b = a;
}
};
template <typename T>
class C : public B<T> {
public:
using B<T>::b; // Doesn't find these in the name resolution
using B<T>::a; // so just make them explicitly visible
C() //: a(20)
{
b = a +11;
}
};
int main() {
C<double> x;
return 0;
}