I am quite used to work with Matlab, hence my code is fully vectorized,
however :
- some parts of my code cannot be vectorized (optimization loops, etc)
- some other parts are really not natural when written in a vectorized
way. Thus writting, reading, debugging and maintaining them is a pain.
But basically, I just would like to see the speed gain I can achieve
with a lower level language on some parts of my code.
Then depending on the performances of the forthcoming JIT compiler of
Scilab, I may consider to translate (or not) my code in fortran.
Pierre Vuillemin
Le mercredi 05 février 2014 à 12:38 +, Carrico, Paul a écrit :
All
before using fortan code, did you have a look to the vectorization in
order to avoid loops (that drastically decrease speed) and to increase
speedup consequently ?
Just an advice
Paul
-Message d'origine-
De : users [mailto:users-boun...@lists.scilab.org] De la part de Pierre
Vuillemin
Envoyé : mercredi 5 février 2014 09:56
À : users@lists.scilab.org
Objet : [Scilab-users] Interfacing fortran code with scilab
Hello all,
I am currently learning fortran in order to speed up some part o my code and
I would like to interface it with Scilab.
To make some tests, I have used this fortran code :
subroutine matmul(C,A,B,m,n,p)
integer ::m,n,p,i,j,k
real(kind=8),dimension(m,n),intent(in)::A
real(kind=8),dimension(n,p),intent(in)::B
real(kind=8),dimension(m,p),intent(out)::C
real(kind=8):: temp
C = 0
do j =1,p
do k=1,n
temp = B(k,j)
do i=1,m
C(i,j)=C(i,j) + A(i,k)*temp
end do
end do
end do
end subroutine matmul
which performs a matrix multiplication. Then I have used 'ilib_for_link'
to create the link.
It works but I have some questions :
- I did the same thing in Python with f2py and the code is seemingly faster
in python, I was wondering why ? (the precision is the same)
- If I change the 'kind = 8' to 'kind = 4' in the fortran code, the function
returns a result which completely wrong.
I expected it to be wrong, but not that much : for instance, with A = 10 and
B = 20, the call to the fortran function gives me '6.36D-314'
What is the reason? (My comprehension of how fortran types work with the kind
parameter is still limited, I know that kind=8 and kind=4 is not a very
portable expression though)
- If I replace
real(kind=8),dimension(m,p),intent(out)::C
by
real(kind=8),dimension(:,:),intent(out)::C
I get a segfault in Scilab or it just closes. I was wondering why ? (I
thought it was something valid since gfortran still compiles)
- Is it possible to keep the upper case in the name of fortran functions when
linked to scilab ? (At the beginning, my function was called 'matMul' and it
took me some time to figure out what the error message 'matMul is not an
entry point' meant)
Best regards,
Pierre Vuillemin
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