如何使用 boost::multiprecision 更改运行时数字精度
how to change at runtime number precision with boost::multiprecision
我读过 boost::multiprecision documentation:
Depending upon the number type, precision may be arbitrarily large (limited only by available memory), fixed at compile time (for example 50 or 100 decimal digits), or a variable controlled at run-time by member functions. The types are expression-template-enabled for better performance than naive user-defined types.
我阅读了更多文档，但没有发现任何关于在运行时更改精度的信息。我只看到允许我在编译时设置精度的模板，这不是我想要的（我想创建一个使用非常高的缩放因子缩放分形的程序）。
如何创建允许我在运行时更改其精度的双精度类型？
大多数号码后端只有固定容量可选。
还要注意一些后端（值得注意的是 cpp 后端）采用分配器，因此它们/隐式/根据需要增长（直到给定限制）：
Normally cpp_bin_float allocates no memory: all of the space required for its digits are allocated directly within the class. As a result care should be taken not to use the class with too high a digit count as stack space requirements can grow out of control. If that represents a problem then providing an allocator as a template parameter causes cpp_bin_float to dynamically allocate the memory it needs
让我查看最流行后端的文档：
gmp 的 mpf_float 坚持这一点：
typedef number<gmp_float<0> > mpf_float;
Type gmp_float can be used at fixed precision by specifying a non-zero Digits10 template parameter, or at variable precision by setting the template argument to zero.
The typedef mpf_float provides a variable precision type whose
precision can be controlled via the numbers member functions.
MPFR 后端类似：
Type mpfr_float_backend can be used at fixed precision by specifying a non-zero Digits10 template parameter, or at variable precision by setting the template argument to zero.
The typedef mpfr_float provides a variable precision type whose precision can be controlled via the numbers member functions.
动态精度用法示例：
// Operations at variable precision and no numeric_limits support:
mpfr_float a = 2;
mpfr_float::default_precision(1000);
std::cout << mpfr_float::default_precision() << std::endl;
std::cout << sqrt(a) << std::endl; // print root-2
它将留下 numeric_limits 未定义
我读过 boost::multiprecision documentation:
Depending upon the number type, precision may be arbitrarily large (limited only by available memory), fixed at compile time (for example 50 or 100 decimal digits), or a variable controlled at run-time by member functions. The types are expression-template-enabled for better performance than naive user-defined types.
我阅读了更多文档，但没有发现任何关于在运行时更改精度的信息。我只看到允许我在编译时设置精度的模板，这不是我想要的（我想创建一个使用非常高的缩放因子缩放分形的程序）。
如何创建允许我在运行时更改其精度的双精度类型？
大多数号码后端只有固定容量可选。
还要注意一些后端（值得注意的是 cpp 后端）采用分配器，因此它们/隐式/根据需要增长（直到给定限制）：
Normally
cpp_bin_floatallocates no memory: all of the space required for its digits are allocated directly within the class. As a result care should be taken not to use the class with too high a digit count as stack space requirements can grow out of control. If that represents a problem then providing an allocator as a template parameter causescpp_bin_floatto dynamically allocate the memory it needs
让我查看最流行后端的文档：
gmp 的
mpf_float坚持这一点：typedef number<gmp_float<0> > mpf_float;Type gmp_float can be used at fixed precision by specifying a non-zero Digits10 template parameter, or at variable precision by setting the template argument to zero.
The
typedef mpf_floatprovides a variable precision type whose precision can be controlled via the numbers member functions.MPFR 后端类似：
Type
mpfr_float_backendcan be used at fixed precision by specifying a non-zero Digits10 template parameter, or at variable precision by setting the template argument to zero.The typedef mpfr_float provides a variable precision type whose precision can be controlled via the numbers member functions.
动态精度用法示例：
// Operations at variable precision and no numeric_limits support:
mpfr_float a = 2;
mpfr_float::default_precision(1000);
std::cout << mpfr_float::default_precision() << std::endl;
std::cout << sqrt(a) << std::endl; // print root-2
它将留下 numeric_limits 未定义