fortran中allocatable的用法
时间: 2023-07-08 16:22:54 浏览: 676
在Fortran中,allocatable是一种动态内存分配方式,可以在程序运行时根据需要动态地分配或释放内存。
使用allocatable,需要在变量声明时加上allocatable关键字,例如:
```
real, allocatable :: a(:,:)
```
这样声明的变量a是一个动态数组,其大小可以在程序运行时进行分配和释放。在程序中,可以使用allocate语句来为allocatable变量分配内存,例如:
```
allocate(a(10,10))
```
这将为变量a分配一个10行10列的二维数组空间。当变量a不再需要时,可以使用deallocate语句释放其占用的内存,例如:
```
deallocate(a)
```
这将释放变量a占用的内存空间。需要注意的是,使用allocatable动态内存分配时,必须确保分配的内存空间不会超出计算机系统的物理内存空间限制,否则程序可能会出现内存溢出的错误。
相关问题
fortran allocatable
Fortran `allocatable` is a feature that allows programmers to dynamically allocate memory for arrays, without having to specify the size at compile time. This makes it easier to write more flexible and efficient code, since the size of the array can be determined at run time based on the needs of the program.
To use `allocatable` arrays in Fortran, you must declare the array as `allocatable` using the `allocate` statement. For example:
```
real, allocatable :: my_array(:,:)
allocate(my_array(100,100))
```
This declares a two-dimensional `real` array called `my_array` that can be dynamically allocated with the `allocate` statement. In this case, we allocate the array to have 100 rows and 100 columns.
Once the array has been allocated, you can use it like any other Fortran array. When you are finished with the array, you should deallocate it using the `deallocate` statement:
```
deallocate(my_array)
```
This frees up the memory that was allocated for the array, allowing it to be used for other purposes.
fortran中real用法
在Fortran中,`real`是用来声明实数类型的关键字。它可以用于声明实数变量、参数、函数返回值等。下面是一些`real`的常见用法:
1. 声明实数变量:
```fortran
real :: x
real(kind=8) :: y ! 声明一个双精度实数变量
```
2. 声明实数数组:
```fortran
real :: a(10) ! 声明一个包含10个实数元素的数组
real(kind=8) :: b(5, 5) ! 声明一个5x5的双精度实数数组
```
3. 在过程参数中使用:
```fortran
subroutine my_subroutine(x, y)
real, intent(in) :: x
real, intent(out) :: y
! ...
end subroutine my_subroutine
```
4. 函数返回值:
```fortran
real function my_function(a, b)
real, intent(in) :: a, b
! ...
end function my_function
```
5. 类型转换:
```fortran
real :: x
x = real(5, kind=8) ! 将整数5转换为双精度实数并赋值给x
```
注意,`real`关键字后面可以使用`kind`参数来指定实数的精度。常见的精度包括`kind=4`(单精度)和`kind=8`(双精度),但具体的精度取决于编译器和系统。如果不指定`kind`参数,默认使用系统默认的实数精度。