包含多个数组的FORTRAN指针 [英] FORTRAN pointer encompassing multiple arrays

问题描述

我正在一个项目中，尽管在第4维中大小可能有所不同，但在第1维，第2维和第3维中有许多相同大小的数组.

I'm working on a project where I have a number of arrays of the same size in the 1st, 2nd and 3rd dimension, although the sizes may vary in the 4th dimension.

我想通过构造一个连接这些数组的指针来对这些数组进行分组.

I would like to group these arrays by constructing a pointer which concatenates these arrays.

为了使这一点变得不那么抽象，假设我有2个数组:

To make this less abstract, let's say I have 2 arrays:

A (size: N1 x N2 x N3 x N4a)
B (size: N1 x N2 x N3 x N4b)

在项目的早期版本中，

将这些数组复制到大小为N1 x N2 x N3 x (N4a + N4b)的数组C中，然后将其传递给子例程以对该数组执行ffts.

in previous versions of the project these arrays where copied to an array C of size N1 x N2 x N3 x (N4a + N4b) which would then be passed to a subroutine to perform ffts on this array.

我想避免这种复制操作，并构造一个指针p，该指针将包含与先前版本中的数组C相同的数据，但没有显式复制和额外的内存分配.

I would like to avoid this copying operation and construct a pointer p which would contain the same data as the array C in the previous version but without the explicit copying and additional memory allocation.

在Fortran中有可能吗?

Is this possible in Fortran?

推荐答案

否.指针不能同时指向两个原本独立的对象.

No. A pointer cannot point across two otherwise independent objects like that at the same time.

根据您的情况，可行的方法是从维数为(N1，N2，N3，N4a + N4b)的数组开始，然后将A和B关联(指针，存储或参数)初始大数组的某些部分.

Depending on your situation, what might be workable is to start with an array that is of dimension (N1,N2,N3,N4a+N4b) and then make A and B associated (pointer, storage or argument) to the relevant parts of that initial big array in some way.

REAL, TARGET :: c(N1,N2,N3,N4a+N4b)
REAL, POINTER :: a(:,:,:,:)
REAL, POINTER :: b(:,:,:,:)

a => c(:,:,:,:n4a)
b => c(:,:,:,n4a+1:)
! Go forth and do things with a and b.

! Then later do things with c.

在黑暗时期，在Fortran进行任何类型的动态内存分配之前，通常将这种一元化到规则化的方法分解开来.

In the dark times, before Fortran had dynamic memory allocation of any sort, this sort of one-array-to-rule-them-all that then got divvied out was in common usage.

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