Fortran的内部内存表示可分配

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  使用数组描述符（也称为dope向量）处理可分配数组，指针数组以及假设的形状数组参数 .

  任何编译器都可以拥有自己的数组描述符结构 . 它可以在编译器手册中找到 . 但是描述符有一种标准化格式，用于与C（以及可能与C通信的Fortran之外的其他软件）进行通信 .

  编译器内部可能不会使用此标准描述符，但它可以是 . 如果它也在内部使用，那么编译器在调用C可互操作过程时不必准备新的描述符 . 例如，gfortran计划支持标准描述符"preferably as native format" .

  英特尔在https://software.intel.com/en-us/node/678452描述了与C可互操作数据描述符不同的本机数组描述符的示例 .

  C-可互操作数组参数的数组描述符的结构由技术规范ISO / IEC TS 29113：2012定义，关于Fortran与C的进一步互操作性，它将成为Fortran 2015的一部分 .

  在C头文件中 ISO_Fortran_binding.h 定义了一个C结构，它用Fortran描述符定义（假设形状，指针或可分配） .

  它看起来如下（从IBM website，某些细节可能是编译器特定的）：

  CFI_cdesc_t 
      A type definition that describes a C descriptor. It contains the following structure members:
  
  void *base_addr
      The base address of the data object that is described. For deallocated allocatable objects, base_addr is NULL. 
  size_t elem_len
  
          For scalars: The size in bytes of the data object that is described.
          For arrays: The size in bytes of one element of the array.
  
  int version
      The version number of the C descriptor. Currently, the only valid value is available by using the CFI_VERSION macro.
  CFI_attribute_t attribute
      The attribute code of the C descriptor. For the valid values for attribute, see Table 1.
  CFI_type_t type
      The type code of the C descriptor. Describes the type of the object that is described by the C descriptor. For the valid values for type, see Table 2. 
  
  CFI_rank_t rank
      The rank of the object that is described by the C descriptor. Its value must be in the range 0 ≤ rank ≤ CFI_MAX_RANK. A value of 0 indicates that the object is a scalar. Otherwise, the object is an array.
  CFI_dim_t dim[]
      An array of size rank that describes the lower bound, extent, and stride of each dimension.
  
  There is a reserved area between rank and dim. The size of the reserved area is 12 words in 32-bit mode and 9 words in 64-bit mode.
  

  引用的 CFI_ 类型也在 ISO_Fortran_binding.h 标头中定义 .

  So, even-though this descriptor may not be exactly the same that your compiler is using internally, it is a good example of what kind of data components one should expect in a Fortran array descriptor.

  但是，请注意gfortran（一种非常常见的编译器）尚未使用此类描述符 . 只有experimental version with the new descriptor，手册中描述了当前描述符 .

  回复于 2024-04-28T19:12:20+08:00