Hi,
Thanks all works now! The implicit none only didn't work when defining
dv as a function now its a subroutine it seems to work.
Regards
Jon
On 12/01/2010 13:44, Pearu Peterson wrote:
Hi,
The problem is that f2py does not support callbacks that
return arrays. There is easy workaround to that: provide
returnable arrays as arguments to callback functions.
Using your example:
SUBROUTINE CallbackTest(dv,v0,Vout,N)
IMPLICIT NONE
!F2PY intent( hide ):: N
INTEGER:: N, ic
EXTERNAL:: dv
DOUBLE PRECISION, DIMENSION( N ), INTENT(IN):: v0
DOUBLE PRECISION, DIMENSION( N ), INTENT(OUT):: Vout
DOUBLE PRECISION, DIMENSION( N ):: Vnow
DOUBLE PRECISION, DIMENSION( N ):: temp
Vnow = v0
!f2py intent (out) temp
call dv(temp, Vnow, N)
DO ic = 1, N
Vout( ic ) = temp(ic)
END DO
END SUBROUTINE CallbackTest
$ f2py -c test.f90 -m t --fcompiler=gnu95
from numpy import *
from t import *
arr = array([2.0, 4.0, 6.0, 8.0])
def dV(v):
print 'in Python dV: V is: ',v
ret = v.copy()
ret[1] = 100.0
return ret
...
output = callbacktest(dV, arr)
in Python dV: V is: [ 2. 4. 6. 8.]
output
array([ 2., 100.,6.,8.])
What problems do you have with implicit none? It works
fine here. Check the format of your source code,
if it is free then use `.f90` extension, not `.f`.
HTH,
Pearu
Jon Moore wrote:
Hi,
I'm trying to build a differential equation integrator and later a
stochastic differential equation integrator.
I'm having trouble getting f2py to work where the callback itself
receives an array from the Fortran routine does some work on it and then
passes an array back.
For the stoachastic integrator I'll need 2 callbacks both dealing with
arrays.
The idea is the code that never changes (ie the integrator) will be in
Fortran and the code that changes (ie the callbacks defining
differential equations) will be different for each problem.
To test the idea I've written basic code which should pass an array back
and forth between Python and Fortran if it works right.
Here is some code which doesn't work properly:-
SUBROUTINE CallbackTest(dv,v0,Vout,N)
!IMPLICIT NONE
cF2PY intent( hide ):: N
INTEGER:: N, ic
EXTERNAL:: dv
DOUBLE PRECISION, DIMENSION( N ), INTENT(IN):: v0
DOUBLE PRECISION, DIMENSION( N ), INTENT(OUT):: Vout
DOUBLE PRECISION, DIMENSION( N ):: Vnow
DOUBLE PRECISION, DIMENSION( N ):: temp
Vnow = v0
temp = dv(Vnow, N)
DO ic = 1, N
Vout( ic ) = temp(ic)
END DO
END SUBROUTINE CallbackTest
When I test it with this python code I find the code just replicates the
first term of the array!
from numpy import *
import callback as c
def dV(v):
print 'in Python dV: V is: ',v
return v.copy()
arr = array([2.0, 4.0, 6.0, 8.0])
print 'Arr is: ', arr
output = c.CallbackTest(dV, arr)
print 'Out is: ', output
Arr is: [ 2. 4. 6. 8.]
in Python dV: V is: [ 2. 4. 6. 8.]
Out is: [ 2. 2. 2. 2.]
Any ideas how I should do this, and also how do I get the code to work
with implicit none not commented out?
Thanks
Jon
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