Thanks Travis, I guess we'll have to tweak the fortran subroutines. It would have been neat though.
David Answer: Since g+=1 adds one to all N elements of g, the buffer a gets incremented N times. So a = array(i) g = ndarray(shape=(1,N), dtype=int, buffer=a, strides=(0,0)) g+=M returns i + M*N 2006/12/6, Travis Oliphant <[EMAIL PROTECTED]>:
David Huard wrote: > Hi, > > I have fortran subroutines wrapped with f2py that take arrays as > arguments, and I often need to use resize(a, N) to pass an array of > copies of an element. The resize call , however, is becoming the speed > bottleneck, so my question is: > Is it possible to create an (1xN) array from a scalar without > allocating additional memory for the array, ie just return a new > "view" of the array where all elements point to the same scalar. > I don't think this would be possible in Fortran because Fortran does not provide a facility for using arbitrary striding (maybe later versions of Fortran using pointers does, though). If you can use arbitrary striding in your code, then you can construct such a view using appropriate strides (i.e. a stride of 0). You can do this with the ndarray constructor: a = array(5) g = ndarray(shape=(1,10), dtype=int, buffer=a, strides=(0,0)) But, notice you will get interesting results using g += 1 Explain why the result of this is an array of 15 (Hint: look at the value of a). -Travis _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
_______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
