傳遞布爾數組而不用`f2py`複製？

Question

如果我打算將一個布爾型的NumPy數組與f2py一起傳遞給Fortran變量，應該如何輸入？我已嘗試integer*1和logical*1，但這些都表明數組已被複制。

例如，如果我編譯文件，foo.f95，包含：

subroutine foo(x, n) 
    logical*1 x(n) 
    !f2py intent(in) x 
    !f2py intent(hide), depend(x) :: n=shape(x,0) 
    ... 
end subroutine 

與f2py -c -m foo foo.f90 -DF2PY_REPORT_ON_ARRAY_COPY=1和運行是這樣的：

import numpy as np 
import foo 
x = np.random.randn(100) < 0 
foo.foo(x) 

它打印

copied an array: size=100, elsize=1 

我得到的如果我將logical*1更改爲，結果相同。什麼是Fortran文件中布爾數組的適當類型，以便數組不被複制？

請注意，由於陣列是1D，因此這不是存儲器連續性的問題 - foo.foo(np.asfortranarray(x))會打印相同的副本消息。

Answer 1

從一些實驗（*）看來，Python/f2py認爲np.int8與logical*1兼容，而np.bool或np.bool8不是由於某些原因。插入print *, "(fort) x = ", x成foo.f90後，我們得到：

>>> foo.foo(np.array([ True, False, False ], dtype=np.bool)) 
copied an array: size=3, elsize=1 
(fort) x = T F F 
>>> foo.foo(np.array([ False, True, False ], dtype=np.bool8)) 
copied an array: size=3, elsize=1 
(fort) x = F T F 
>>> foo.foo(np.array([ False, False, True ], dtype=np.int8)) # no copy 
(fort) x = F F T 

由於True和False被簡單地映射到1和0，使用在Python端的int8陣列可以是方便。

---

（*）一些實驗

在這裏，我改變了f2py意圖註釋inout，看看我們是否可以從Fortran語言方面修改數組。

foo.f90：

subroutine foo(x, n) 
    use iso_c_binding 
    implicit none 
    integer n 
    logical*1 x(n) 
    ! logical x(n) 
    ! logical(c_bool) x(n) 

    !f2py intent(inout) x 
    !f2py intent(hide), depend(x) :: n=shape(x,0) 

    print *, "(fort) x = ", x 
    print *, "(fort) sizeof(x(1)) = ", sizeof(x(1)) 
    print *, "(fort) resetting x(:) to true" 
    x(:) = .true. 
end subroutine 

test.py：

import numpy as np 
import foo 

for T in [ np.bool, np.bool8, 
      np.int, np.int8, np.int32, np.int64, 
      np.uint, np.uint8, np.uint32, np.uint64, 
      np.dtype('b'), np.dtype('int8'), np.dtype('int32') ]: 

    print("-------------------------") 
    print("dtype =", T) 

    x = np.array([ True, False, True ], dtype=T) 
    print("input x =", x) 

    try: 
     foo.foo(x) 
     print("output x =", x) 
    except: 
     print("failed") 

結果與logical*1：

------------------------- 
dtype = <class 'bool'> 
input x = [ True False True] 
failed 
------------------------- 
dtype = <class 'numpy.bool_'> 
input x = [ True False True] 
failed 
------------------------- 
dtype = <class 'int'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.int8'> 
input x = [1 0 1] 
(fort) x = T F T 
(fort) sizeof(x(1)) =      1 
(fort) resetting x(:) to true 
output x = [1 1 1] 
------------------------- 
dtype = <class 'numpy.int32'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.int64'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.uint64'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.uint8'> 
input x = [1 0 1] 
(fort) x = T F T 
(fort) sizeof(x(1)) =      1 
(fort) resetting x(:) to true 
output x = [1 1 1] 
------------------------- 
dtype = <class 'numpy.uint32'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.uint64'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = int8 
input x = [1 0 1] 
(fort) x = T F T 
(fort) sizeof(x(1)) =      1 
(fort) resetting x(:) to true 
output x = [1 1 1] 
------------------------- 
dtype = int8 
input x = [1 0 1] 
(fort) x = T F T 
(fort) sizeof(x(1)) =      1 
(fort) resetting x(:) to true 
output x = [1 1 1] 
------------------------- 
dtype = int32 
input x = [1 0 1] 
failed 

結果與logical（默認的那種）：

------------------------- 
dtype = <class 'bool'> 
input x = [ True False True] 
failed 
------------------------- 
dtype = <class 'numpy.bool_'> 
input x = [ True False True] 
failed 
------------------------- 
dtype = <class 'int'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.int8'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.int32'> 
input x = [1 0 1] 
(fort) x = T F T 
(fort) sizeof(x(1)) =      4 
(fort) resetting x(:) to true 
output x = [1 1 1] 
------------------------- 
dtype = <class 'numpy.int64'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.uint64'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.uint8'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.uint32'> 
input x = [1 0 1] 
(fort) x = T F T 
(fort) sizeof(x(1)) =      4 
(fort) resetting x(:) to true 
output x = [1 1 1] 
------------------------- 
dtype = <class 'numpy.uint64'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = int8 
input x = [1 0 1] 
failed 
------------------------- 
dtype = int8 
input x = [1 0 1] 
failed 
------------------------- 
dtype = int32 
input x = [1 0 1] 
(fort) x = T F T 
(fort) sizeof(x(1)) =      4 
(fort) resetting x(:) to true 
output x = [1 1 1] 

結果與logical(c_bool)（通過ISO_C_BINDING）：

------------------------- 
dtype = <class 'bool'> 
input x = [ True False True] 
failed 
------------------------- 
dtype = <class 'numpy.bool_'> 
input x = [ True False True] 
failed 
------------------------- 
dtype = <class 'int'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.int8'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.int32'> 
input x = [1 0 1] 
(fort) x = T F F 
(fort) sizeof(x(1)) =      1 
(fort) resetting x(:) to true 
output x = [65793  0  1] 
------------------------- 
dtype = <class 'numpy.int64'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.uint64'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.uint8'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = <class 'numpy.uint32'> 
input x = [1 0 1] 
(fort) x = T F F 
(fort) sizeof(x(1)) =      1 
(fort) resetting x(:) to true 
output x = [65793  0  1] 
------------------------- 
dtype = <class 'numpy.uint64'> 
input x = [1 0 1] 
failed 
------------------------- 
dtype = int8 
input x = [1 0 1] 
failed 
------------------------- 
dtype = int8 
input x = [1 0 1] 
failed 
------------------------- 
dtype = int32 
input x = [1 0 1] 
(fort) x = T F F 
(fort) sizeof(x(1)) =      1 
(fort) resetting x(:) to true 
output x = [65793  0  1] 

出於某種原因，這最後logical(c_bool)不符合上述使用工作...（f2py似乎認爲logical(c_bool)爲4個字節，而gfortran對待它作爲1個字節，所以有些不一致......）