[Numpy-discussion] String sort

Charles R Harris charlesr.harris@gmail....
Fri Feb 8 13:30:07 CST 2008


On Feb 8, 2008 11:07 AM, Charles R Harris <charlesr.harris@gmail.com> wrote:

>
>
> On Feb 8, 2008 10:31 AM, Francesc Altet <faltet@carabos.com> wrote:
>
> > A Friday 08 February 2008, Francesc Altet escrigué:
> > > A Friday 08 February 2008, Charles R Harris escrigué:
> > > > > Also, in the context of my work in indexing, and because of the
> > > > > slowness of the current implementation in NumPy, I've ended with
> > > > > an implementation of the quicksort method for 1-D array strings.
> > > > > For moderately large arrays, it is about 2.5x-3x faster than the
> > > > > (supposedly) mergesort version in NumPy, not only due to the
> > > > > quicksort, but also because I've implemented a couple of macros
> > > > > for efficient string swapping and copy.  If this is of interest
> > > > > for NumPy developers, tell me and I will provide the code.
> > > >
> > > > I have some code for this too and was going to merge it. Send yours
> > > > along and I'll get to it this weekend.
> > >
> > > Ok, great.  I'm attaching it.  Tell me if you need some clarification
> > > on the code.
> >
> > Ops.  I've introduced a last-minute problem in my code.  To fix this,
> > just replace the flawed opt_strncmp() that I sent before by:
> >
> > static int inline opt_strncmp(char *a, char *b, int n) {
> >  int i;
> >  for (i=0; i<n; i++) {
> >    if (a[i] > b[i]) return i+1;
> >    if (a[i] < b[i]) return -(i+1);
> >    /* Another way, but seems equivalent in speed, at least here */
> > /*     if (a[i] != b[i]) */
> > /*       return (((unsigned char *)a)[i] - ((unsigned char *)b)[i]); */
> >  }
> >  return 0;
> > }
> >
> > Apparently, this version works just fine.
> >
>
> Did you find this significantly faster than strncmp? There is also a
> unicode compare, do you have thoughts about that?
>

Does anyone know if inline is compiler safe/portable these days. There are
definitely places where I would like to use it, but I've been hesitant.

Chuck
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