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Re: FindCurvePath has a problem

• To: mathgroup at smc.vnet.net
• Subject: [mg127422] Re: FindCurvePath has a problem
• From: Oliver Ruebenkoenig <ruebenko at wolfram.com>
• Date: Mon, 23 Jul 2012 19:55:52 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• Delivered-to: mathgroup-newout@smc.vnet.net
• Delivered-to: mathgroup-newsend@smc.vnet.net
• References: <20120721034120.2CB6F68C2@smc.vnet.net>

On Fri, 20 Jul 2012, Oliver Ruebenkoenig wrote:

>
>
> On Fri, 20 Jul 2012, Ralph Dratman wrote:
>
>> The following input to FindCurvePath produces the output shown below it:
>>
>> FindCurvePath[{{278,141},{279,141},{279,142},{279,143},{280,143},{280,144},
>> {280,145},{280,146},{281,147},{281,148},{281,149},{281,150},{282,150},{282,
>> 151},{282,152},{283,151},{283,152},{283,153},{284,153},{284,154},{285,155},
>> {286,155},{286,156},{287,156},{287,157},{288,157},{289,156},{290,156},{290,
>> 157},{291,156},{291,157},{292,156},{292,157},{293,156},{293,157},{294,156},
>> {294,157},{295,156},{295,157},{296,156},{296,157},{297,156},{297,157},{298,
>> 155},{298,156},{299,155},{299,156},{300,155},{301,154},{301,155},{302,153},
>> {302,154},{303,152},{303,153},{304,150},{304,151},{304,152},{305,149},{305,
>> 150},{306,146},{306,147},(*{306,148},{306,149},{307,144},{307,145},{307,146
>> },{308,141},{308,142},{308,143},{308,144},{309,139},{309,140},{309,141},{31
>> 0,138},{310,139},{311,136},{311,137},{311,138},{312,135},{312,136},{313,134
>> },{313,135},*){314,133},{314,134}}]
>> FindCurvePath::ntri:    The data generates an inconsistent
>> triangulation. You can perturb the data to make it valid. >>
>> Fail
>>
>> If you restore the commented-out list elements (beginning with
>> (*{306,148}...), then evaluate, you get an apparently never-ending
>> silent hangup, which is of course far worse than an error message.
>>
>> I have not yet tried to "perturb" anything to work around the problem.
>> Clearly the function needs to check its arguments before wandering off
>> into lala land.
>>
>>
>> Ralph Dratman
>>
>>
>
> The only oddity is that it returns Fail in stead of $Failed, other than
> that works on Linux-x86-64 V8.0.4. What version/OS do you have?
>
> Oliver
>
>

Unfortunately, I must correct myself here, since I do see the hang as well. A
copy and paste error made the data set work. Sorry about that. I filed 
this as a something too look at.

This data set still works:

FindCurvePath[{{278, 141}, {279, 141}, {279, 142}, {279, 143}, {280,
    143}, {280, 144}, {280, 145}, {280, 146}, {281, 147}, {281,
    148}, {281, 149}, {281, 150}, {282, 150}, {282, 151}, {282,
    152}, {283, 151}, {283, 152}, {283, 153}, {284, 153}, {284,
    154}, {285, 155}, {286, 155}, {286, 156}, {287, 156}, {287,
    157}, {288, 157}, {289, 156}, {290, 156}, {290, 157}, {291,
    156}, {291, 157}, {292, 156}, {292, 157}, {293, 156}, {293,
    157}, {294, 156}, {294, 157}, {295, 156}, {295, 157}, {296,
    156}, {296, 157}, {297, 156}, {297, 157}, {298, 155}, {298,
    156}, {299, 155}, {299, 156}, {300, 155}, {301, 154}, {301,
    155}, {302, 153}, {302, 154}, {303, 152}
   , {303, 153}, {304, 150}, {304, 151}, {304, 152}, {305, 149}, {305,
    150}, {306, 146}, {306, 147}, {306, 148}, {306, 149}, {307,
    144}, {307, 145}
   , {307, 146}, {308, 141}, {308, 142}, {308, 143}, {308, 144}, {309,
    139}
   , {309, 140}, {309, 141}, {310, 138}, {310, 139}, {311, 136}, {311,
    137}
   , {311, 138}, {312, 135}, {312, 136}, {313, 134}
   , {313, 135}
   (*,{314,133},{314,134}*)}]

Oliver

• References:
  • Re: FindCurvePath has a problem
    • From: Oliver Ruebenkoenig <ruebenko@wolfram.com>