python Easy to write, but speedy ~ → Bottleneck modularized fortran !! !! !! fast! !! !!

Let's modularize the prime number display program I wrote earlier for the purpose of practicing Fortran.

environment

f2py (included with scipy) gfortran4.7.2

script

Prepare a file that describes the subroutine you want to modularize. The argument of the subroutine declares in with Cf2py. The return value of the subroutine (that is, the return value received on the python side) declares out with Cf2py. If you do not write the Cf2py declaration from the beginning of the line and open 6 spaces in the script body, a compile error will occur. Apparently, I have to write it indented after Cf2py (it's annoying !!)

`primepy.f90`


      subroutine prime_number(max_num, ret)
         implicit none
         integer max_num
         integer ret(max_num)
         integer i, j, list(max_num)
Cf2py intent(in) max_num
Cf2py intent(out) ret
         
         !set l
         do i=1, max_num, 1
            list(i) = i
         enddo
         list(1) = 0

         !Set a prime number
         do i=1, max_num, 1
            if (.not. list(i) == 0) then
               do j = i*2, max_num, i
                  list(j) = 0
               end do
            endif
         enddo

         !Returns a list of prime numbers
         do i=1, max_num, 1
            ret(i) = list(i)
         enddo
      end subroutine prime_number

compile

f2py -c --fcompiler=gfortran -m prime primepy.f90 Compile with -c Specify the compiler with --fcompiler Output file after -m Finally the Fortran program files Then check help with -h

Success if prime.so file is created.

Run

With a python interpreter

>>> import prime
>>> a = prime.prime_number(100)
>>> a
array([ 0,  2,  3,  0,  5,  0,  7,  0,  0,  0, 11,  0, 13,  0,  0,  0, 17,
        0, 19,  0,  0,  0, 23,  0,  0,  0,  0,  0, 29,  0, 31,  0,  0,  0,
        0,  0, 37,  0,  0,  0, 41,  0, 43,  0,  0,  0, 47,  0,  0,  0,  0,
        0, 53,  0,  0,  0,  0,  0, 59,  0, 61,  0,  0,  0,  0,  0, 67,  0,
        0,  0, 71,  0, 73,  0,  0,  0,  0,  0, 79,  0,  0,  0, 83,  0,  0,
        0,  0,  0, 89,  0,  0,  0,  0,  0,  0,  0, 97,  0,  0,  0], dtype=int32)

Water

I couldn't think of an easy way to return only non-zero, so this is ʻa.take (a.nonzero () [0])` on the python side.

Conclusion

Happy to eliminate bottlenecks If you don't understand with fortran, handle it on the python side! !! The best list of python! !! !!

Write python modules in fortran using f2py

environment

script

primepy.f90

compile

Run

Conclusion

`primepy.f90`