# [Baypiggies] Hi all -can anyone convert this code to python---many thanks

Mike Cheponis mac at Wireless.Com
Thu Dec 14 21:58:45 CET 2006

```As I see it, the correct answer is to wrap this C function so it's callable from Python.

That way, no recoding, maximum performance.

-Mike

p.s. I'll send a bill later.  You gotta know exactly where to tap the hammer...

On Thu, 14 Dec 2006, Sharon Kazemi wrote:

> Date: Thu, 14 Dec 2006 10:16:31 -0800
> From: Sharon Kazemi <sharonk at gisc.berkeley.edu>
> To: baypiggies at python.org
> Subject: [Baypiggies] Hi all -can anyone convert this code to python---many
>     thanks
>
> Hi all,
>
> have below code that needs to be recoded into Python for use in ESRI ArcGIS
> software.
> I would greatly appreciate any assistance.
> Thanks
> Sheri
>
> /*  The Inner Loop of the Douglas-Peucker line generalization
> algorithm is the process of finding, for a section of a polyline,
> the vertex that is furthest from the line segment joining the
> two endpoints.  The method coded below in C (or C++) is the most
> efficient, in terms of operation counts, that I have seen.  */
> /*  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  */
>
> long FurthestFromSegment ( /* Return index of furthest point.  */
>    long    startindex,    /* Index of start vertex in arrays.  */
>    long    endindex,      /* Index of end vertex in arrays.  */
>    double *x         ,    /* Array, abscissae of polyline vertices. */
>    double *y         ,    /* Array, ordinates of polyline vertices. */
>    double *distMaxSquare  /* Return square of maximum distance.  */
>                         )
>  /*
>   This function, given a section of a polyline in arrays,
>    will return the index of the intermediate node that is furthest
>    from the segment joining the two endpoints of the section,
>    and the square of the distance from the segment.
>
>   If no intermediate point exists, then the returned index will
>    be the index of the start vertex and the returned distance
>    squared will be -1.0 .  Caution:  Do not calculate the square
>    root of this returned value without ruling out the possibility
>    that it may have defaulted to -1.0 .  In a normal
>    Douglas-Peucker application, you should never have to calculate
>    the square root of this output value, and you should never
>    need to invoke this function without intermediate points.
>  */
> {
>      /*
>       The variable names below assume we find
>         the distance of point "A" from segment "BC" .
>      */
>    long index, outindex ;
>    double distSquare, bcSquare ;
>    double cx, cy, bx, by, ax, ay ;
>    double bcx, bcy, bax, bay, cax, cay ;
>
>    *distMaxSquare  =  -1.0 ;
>    if ( endindex  <  startindex + 2 )    return startindex ;
>    outindex  =  startindex ;
>    bx  =  x[startindex] ;
>    by  =  y[startindex] ;
>    cx  =  x[endindex] ;
>    cy  =  y[endindex] ;
>      /* Find vector BC and the Square of its length.  */
>    bcx  =  cx - bx ;
>    bcy  =  cy - by ;
>    bcSquare  =  bcx * bcx  +  bcy * bcy ;
>      /* The inner loop:  */
>    for ( index = startindex + 1 ; index < endindex ; index++ )
>    {
>          /* Find vector BA .  */
>        ax  =  x[index] ;
>        ay  =  y[index] ;
>        bax  =  ax - bx ;
>        bay  =  ay - by ;
>          /* Do scalar product and check sign.  */
>        if ( bcx * bax  +  bcy * bay    <=    0.0 )
>        {
>              /* Closest point on segment is B; */
>              /*   find its distance (squared) from A .  */
>            distSquare   =   bax * bax  +  bay * bay ;
>        }
>        else
>        {
>              /* Find vector CA .  */
>            cax  =  ax - cx ;
>            cay  =  ay - cy ;
>              /* Do scalar product and check sign.  */
>            if ( bcx * cax  +  bcy * cay    >=    0.0 )
>            {
>                  /* Closest point on segment is C; */
>                  /*   find its distance (squared) from A .  */
>                distSquare   =   cax * cax  +  cay * cay ;
>            }
>            else
>            {
>                  /* Closest point on segment is between B and C; */
>                  /*    Use perpendicular distance formula.  */
>                distSquare    =    cax * bay  -  cay * bax ;
>                distSquare    =    distSquare * distSquare / bcSquare ;
>                      /* Note that if bcSquare be zero, the first
>                          of the three branches will be selected,
>                          so division by zero will not occur here. */
>            }
>        }
>
>        if ( distSquare > *distMaxSquare )
>        {
>            outindex  =  index ;
>            *distMaxSquare  =  distSquare ;
>        }
>    }
>      /*
>         Note that in the inner loop above, if we follow
>         the most common path where the perpendicular
>         distance is the one to calculate, then for each
>         intermediate vertex the float operation count is
>         1 divide, 7 multiplies, 5 subtracts, 1 add, and 2 compares.
>      */
>
>    return outindex ;
> }
>
> Sharon Kazemi
> Visiting Scholar/GIS Analyst
> Geographic Information Science Center
> 412 Wurster Hall
> University of California Berkeley
> Berkeley, CA 94720-1820
> Phone: +1-510-642-2812
> Fax: +1-510-643-3412
> Email: sharonk at gisc.berkeley.edu
> http://www.gisc.berkeley.edu/
>
>
>
> -----Original Message-----
> From: baypiggies-bounces at python.org
> [mailto:baypiggies-bounces at python.org]On Behalf Of
> baypiggies-request at python.org
> Sent: Thursday, December 14, 2006 3:00 AM
> To: baypiggies at python.org
> Subject: Baypiggies Digest, Vol 14, Issue 16
>
>
> Send Baypiggies mailing list submissions to
> 	baypiggies at python.org
>
> To subscribe or unsubscribe via the World Wide Web, visit
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> 	baypiggies-owner at python.org
>
> than "Re: Contents of Baypiggies digest..."
>
>
> Today's Topics:
>
>   1. Re:  Dec. 14 Meeting "Programming Productivity: What	Really
>      Matters?" (Anna Ravenscroft)
>   2. Re:  Dec. 14 Meeting "Programming Productivity: What	Really
>      Matters?" (Shannon -jj Behrens)
>   3. Re:  Dec. 14 Meeting "Programming Productivity: What Really
>      Matters?" (Dennis Reinhardt)
>   4. Re:  Dec. 14 Meeting "Programming Productivity: What	Really
>      Matters?" (Anna Ravenscroft)
>   5. Re:  Dec. 14 Meeting "Programming Productivity: What	Really
>      Matters?" (Marilyn Davis)
>   6. Re:  Dec. 14 Meeting "Programming Productivity: What	Really
>      Matters?" (Anna Ravenscroft)
>   7. Re:  Dec. 14 Meeting "Programming Productivity: What	Really
>      Matters?" (Alex Martelli)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 13 Dec 2006 17:22:03 -0800
> From: "Anna Ravenscroft" <annaraven at gmail.com>
> Subject: Re: [Baypiggies] Dec. 14 Meeting "Programming Productivity:
> 	What	Really Matters?"
> To: "Mike Cheponis" <mac at wireless.com>
> Cc: Python <baypiggies at python.org>
> Message-ID:
> 	<cb361a610612131722v7c6fef90ha4504a604b9b5246 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> On 12/13/06, Mike Cheponis <mac at wireless.com> wrote:
>> "Social Time" is really just "Random Mapping".
>>
>> So, if nobody stands up during "Mapping" you get all "Social Time".  Also,
> those that don't "map" are, by default, in the "Social" mapping...
>>
>> Don't worry, the meetings aren't nearly as formal as our discussions
>>
>> -Mike
>
> I've been to the meetings. Social TIme != mapping.
>
> I don't have time or energy to wait for the formal "mapping" to get
> over with before I can socialize with people. I have a final tomorrow
> and expect to be pretty exhausted and wanting to go to bed early. I
> was looking forward to some generic, informal socializing.
>
> OR can we have some freeform socializing BEFORE the official part of
> the meeting - that way those who want (and have the energy) to do the
> mapping can stay for that?
>
> Anna
>
>
> ------------------------------
>
> Message: 2
> Date: Wed, 13 Dec 2006 18:09:35 -0800
> From: "Shannon -jj Behrens" <jjinux at gmail.com>
> Subject: Re: [Baypiggies] Dec. 14 Meeting "Programming Productivity:
> 	What	Really Matters?"
> To: "Anna Ravenscroft" <annaraven at gmail.com>
> Cc: Python <baypiggies at python.org>, Mike Cheponis <mac at wireless.com>
> Message-ID:
> 	<c41f67b90612131809q37612254i1007ffe3e5fb7667 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> On 12/13/06, Anna Ravenscroft <annaraven at gmail.com> wrote:
>> On 12/13/06, Mike Cheponis <mac at wireless.com> wrote:
>>> "Social Time" is really just "Random Mapping".
>>>
>>> So, if nobody stands up during "Mapping" you get all "Social Time".
> Also, those that don't "map" are, by default, in the "Social" mapping...
>>>
>>> Don't worry, the meetings aren't nearly as formal as our discussions
>>>
>>> -Mike
>>
>> I've been to the meetings. Social TIme != mapping.
>>
>> I don't have time or energy to wait for the formal "mapping" to get
>> over with before I can socialize with people. I have a final tomorrow
>> and expect to be pretty exhausted and wanting to go to bed early. I
>> was looking forward to some generic, informal socializing.
>>
>> OR can we have some freeform socializing BEFORE the official part of
>> the meeting - that way those who want (and have the energy) to do the
>> mapping can stay for that?
>
> It sounds like we have a pretty vocal contingent of people who want 30
> minutes of informal socializing followed by an hour for the actual
> talk.  That's fine by me.
>
> -jj
>
> --
> http://jjinux.blogspot.com/
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 13 Dec 2006 18:17:51 -0800
> From: Dennis Reinhardt <DennisR at dair.com>
> Subject: Re: [Baypiggies] Dec. 14 Meeting "Programming Productivity:
> 	What Really Matters?"
> To: Python <baypiggies at python.org>
> Message-ID: <5.1.0.14.0.20061213173953.023a51d0 at localhost>
> Content-Type: text/plain; charset="us-ascii"; format=flowed
>
> At 05:22 PM 12/13/2006, Anna Ravenscroft wrote:
>
>> OR can we have some freeform socializing BEFORE the official part of
>> the meeting -
>
> Anna,
>
> I have regularly attended the pre-dinner meetings Brian has organized (at
> least the ones at IronPort).  They may well be the social time you are
> looking for and in the time frame you ask for.
>
> If one looks at the agenda template we have had this year, it looks like:
>
>         7:00 - 7:30 unstructured pre-meeting
>         7:30 - 9:00 meeting program
>
> Nothing has prevented people from socializing in the 7:00 - 7:30
> pre-meeting time frame.  By my observation, not that much socialization
> gets done then.  Whatever limiters there are in socializing in the 7:00 to
> 7:30 time frame are likely to affect tomorrow's meeting as well.  Suppose
> we revise the schedule to read
>
>         7:00 - x:yz social
>         x:yz - 9:00 program
>
> I don't think moving the 7:00 earlier is that easy without checking the
> room schedule or someone from Google taking responsibility for being
> there.  Could happen but the fact is that we already have an time preceding
> every meeting where completely unstructured socialization is possible.
>
> Suppose we set x:yz to 7:40, allowing JJ's presentation to take the entire
> 80 minutes.  IMO, we have run that experiment as well and it is called
> starting the meeting 10 minutes late.  I have not seen the demand for that.
>
> The major alternative here is set x:yz to 9:00 and shut down JJ's talk
> entirely.  My sense is that JJ has a great talk planned and while meet and
> greet was preferred to no meeting at all, JJ's unabridged talk and
> free-for-all discussion (i.e. what passes for socialization for some of us)
> is a preferred use of the time available.
>
> If you have not attended the pre-meeting dinners, I can recommend them as a
> good way to socialize.
>
> Dennis
>
>
>  ---------------------------------
> | Dennis    | DennisR at dair.com    |
> | Reinhardt | http://www.dair.com |
>  ---------------------------------
>
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 13 Dec 2006 18:57:16 -0800
> From: "Anna Ravenscroft" <annaraven at gmail.com>
> Subject: Re: [Baypiggies] Dec. 14 Meeting "Programming Productivity:
> 	What	Really Matters?"
> To: "Dennis Reinhardt" <DennisR at dair.com>
> Cc: Python <baypiggies at python.org>
> Message-ID:
> 	<cb361a610612131857r7a3a18c5u20344f1f13398cb7 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Okay - let me describe what I mean by "socializing".
>
> To me, socializing is not:
>
> "mapping" (mapping is a formal structure grouping up people and the
> grouping process seems to take forever.)
>
> dinner (getting stuck next to someone I've never met and have nothing
> in common with and having to make smalltalk with them for the next
> hour is my idea of hell.)
>
> extending the Q&A session after a presentation - leaving those of us
> who have heard enough stuck with the choice of being *rude* or waiting
> patiently in hopes that eventually we can stand up and go talk to
> someone we have been wanting to talk with - which usually happens
> about 5 minutes before we're kicked out of the room...
>
> Milling around in the lobby of google waiting to fill out a badge and
> be shepherded up to a room just in time for the presentation to start.
> Not everyone is there, and we're usually rather distracted.
>
> Socializing - what I'm asking for - is a chance to talk to people, _by
> choice_ -- not by enforced proximity or structured format -- including
> the chance to walk around and talk to more than one person. Having
> snacks and beverages is nice.
>
> I would like a chance to socialize.
>
> Cordially,
> Anna
>
>
> ------------------------------
>
> Message: 5
> Date: Wed, 13 Dec 2006 21:56:50 -0800
> From: Marilyn Davis <marilyn at deliberate.com>
> Subject: Re: [Baypiggies] Dec. 14 Meeting "Programming Productivity:
> 	What	Really Matters?"
> To: baypiggies at python.org
> Message-ID: <20061214055653.9296D1E4006 at bag.python.org>
> Content-Type: text/plain; charset="ISO-8859-1"
>
>
> ----- On Wednesday, December 13, 2006 annaraven at gmail.com wrote:
>
>> Okay - let me describe what I mean by "socializing".
>>
>> To me, socializing is not:
>>
>> "mapping" (mapping is a formal structure grouping up people and the
>> grouping process seems to take forever.)
>>
>> dinner (getting stuck next to someone I've never met and have nothing
>> in common with and having to make smalltalk with them for the next
>> hour is my idea of hell.)
>>
>> extending the Q&A session after a presentation - leaving those of us
>> who have heard enough stuck with the choice of being *rude* or waiting
>> patiently in hopes that eventually we can stand up and go talk to
>> someone we have been wanting to talk with - which usually happens
>> about 5 minutes before we're kicked out of the room...
>>
>> Milling around in the lobby of google waiting to fill out a badge and
>> be shepherded up to a room just in time for the presentation to start.
>> Not everyone is there, and we're usually rather distracted.
>
> Yeh.  We are not allowed in early, as far as I know.  The lobby is not the
> right thing.  We're not there yet.
>
> Google is providing snacks?  How do the snacks get snacked upon if the
> program starts when people first arrive?
>
> So far, it seems to me, this little disagreement we are having is divided
> against the gender axis.  Just commenting, I don't have any judgement or
> conclusion about it, I just find it interesting.
>
> I'm looking forward to whatever part I'm able to get to.
>
> Marilyn
>
>>
>> Socializing - what I'm asking for - is a chance to talk to people, _by
>> choice_ -- not by enforced proximity or structured format -- including
>> the chance to walk around and talk to more than one person. Having
>> snacks and beverages is nice.
>>
>> I would like a chance to socialize.
>>
>> Cordially,
>> Anna
>> _______________________________________________
>> Baypiggies mailing list
>> Baypiggies at python.org
>> http://mail.python.org/mailman/listinfo/baypiggies
>
>
>
>
> ------------------------------
>
> Message: 6
> Date: Wed, 13 Dec 2006 22:06:25 -0800
> From: "Anna Ravenscroft" <annaraven at gmail.com>
> Subject: Re: [Baypiggies] Dec. 14 Meeting "Programming Productivity:
> 	What	Really Matters?"
> To: "Marilyn Davis" <marilyn at deliberate.com>
> Cc: baypiggies at python.org
> Message-ID:
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> On 12/13/06, Marilyn Davis <marilyn at deliberate.com> wrote:
>>
>> ----- On Wednesday, December 13, 2006 annaraven at gmail.com wrote:
>>
>> Yeh.  We are not allowed in early, as far as I know.  The lobby is not the
> right thing.  We're not there yet.
>>
>> Google is providing snacks?  How do the snacks get snacked upon if the
> program starts when people first arrive?
>>
>> So far, it seems to me, this little disagreement we are having is divided
> against the gender axis.  Just commenting, I don't have any judgement or
> conclusion about it, I just find it interesting.
>>
>
> The main disagreement I really see is a different definition of
> socializing. Which is why I posted my definition so we could have the
> discussion be more clear. Some people apparently consider the lobby
> milling or the mapping to be socializing. That's okay for them to have
> that definition - but it's not what I was asking for when I asked for
> a chance to socialize, and so I figured it would be easier to discuss
> if we had a definition on the table. (whether for people to agree or
> disagree with - at least we're not assuming what it means.) Once we
> agree on what it means to "socialize" we can agree on whether we want
> a socializing time.
>
>> I'm looking forward to whatever part I'm able to get to.
>
> Me too. I'm sure the presentation will be great. I hope I get a chance
> to chat with you. I haven't had much opportunity for that.
>
> --
> cordially,
> Anna
> --
> It is fate, but call it Italy if it pleases you, Vicar!
>
>
> ------------------------------
>
> Message: 7
> Date: Wed, 13 Dec 2006 22:54:46 -0800
> From: "Alex Martelli" <aleax at google.com>
> Subject: Re: [Baypiggies] Dec. 14 Meeting "Programming Productivity:
> 	What	Really Matters?"
> To: "Marilyn Davis" <marilyn at deliberate.com>
> Cc: baypiggies at python.org
> Message-ID:
> 	<55dc209b0612132254y6ea79c01h257c2d515fbe6fd6 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> On 12/13/06, Marilyn Davis <marilyn at deliberate.com> wrote:
>   ...
>> So far, it seems to me, this little disagreement we are having is divided
> against the gender axis.  Just commenting, I don't have any judgement or
> conclusion about it, I just find it interesting.
>
> OK, so let me weigh in...: I _know_ I'm going to be seriously tired
> tomorrow night, except (perhaps, with some luck:-) very early on, as
> I'm going to have a long and intense workday before it; so, from my
> subjective POV the tradeoff is -- am I going to be dozing at the end
> of the presentation (if we have socialtime _before_), or am I going to
> be dozing through socialtime (if we have it _after_).  Overall, I'd
> (marginally) prefer the first option.
>
> Sorry to spoil the nice gender-axis alignment, but then, I tend to do
> that (I guess that, according to our great State's great governor,
> this makes me a "girlyman":-).
>
>
>> I'm looking forward to whatever part I'm able to get to.
>
> Likewise, except s/get to/be awake for/ :-).
>
>
> Alex
>
>
> ------------------------------
>
> _______________________________________________
> Baypiggies mailing list
> Baypiggies at python.org
> http://mail.python.org/mailman/listinfo/baypiggies
>
>
> End of Baypiggies Digest, Vol 14, Issue 16
> ******************************************
>
>
>
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>

```