On 1/12/07, Charles R Harris <[EMAIL PROTECTED]> wrote:
On 1/11/07, David Cournapeau <[EMAIL PROTECTED]> wrote: > > Travis Oliphant wrote: > > > > This is one thing I've exposed (and made use of in more than one > place) > > with NumPy. In Numeric, the magic was in a few lines of the > ufuncobject > > file). Now, it is exposed in the concept of an array > iterator. Anybody > > can take advantage of it as it there is a C-API call to get an array > > iterator from the array (it's actually the object returned by the > .flat > > method). You can even get an iterator that iterates over one-less > > dimension than the array has (with the dimension using the smallest > > strides left "un-iterated" so that you can call an inner loop with > it). > The thing which confuses me is whether this is useful when you only one > item of one array at a time. When I was implementing some functions for > LPC, I took a look at your examples for array iterators and explanations > in the numpy ebook, and it looked really helpful, indeed. For this kind > of code, I needed to operate on several contiguous elements at a time. > > But here, for cliping with scalar min and max, I only need to access to > one item at a time from the input array, and that's it; in particular, I > > don't care about the order of iteration. So the question really boils > down to: > > "for a numpy array a of eg float32, am I guaranteed that > a->data[sizeof(float32) * i] for 0 <= i < a.size gives me all the items > of a, even for non contiguous arrays ?" No. That is what the array iterator is for.
Although it is pretty common to make a copy of the array that *is* contiguous and pass that down. Doing so keeps life simple for the programmer and is pretty much required when interfacing to third party c and fortran routines. Chuck
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