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Bug introduced in 10.2.0 or earlier and fixed in 11.0.0


I define an implicit region like

R = ImplicitRegion[
  0 < Sin[u]/Cos[v] < 1 && 
   0 < Sin[v]/Cos[u] < 1, {{u, 0, 2}, {v, 0, 2}}]

But when I try to do

DiscretizeRegion[R]

Mathematica 10.4 seems to hang and doesn't return any result. This is strange, because the region is really just a simple triangle

RegionPlot[0 < Sin[u]/Cos[v] < 1 && 0 < Sin[v]/Cos[u] < 1, {u, 0, 2}, {v, 0, 2}]

triangle

and discretization of a more complex region like

DiscretizeRegion[ImplicitRegion[0 < Sinh[u]/Cosh[v] < 1 && 0 < Sinh[v]/Cosh[u] < 1, 
                 {{u, 0, 2}, {v, 0, 2}}]]

works without problems. What is the problem with my implicit triangle?

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4
  • $\begingroup$ I can confirm that this problem is also present in MM 10.2 running on Mac OS. $\endgroup$ Apr 18, 2016 at 22:20
  • $\begingroup$ With version 10.4 on Windows 7 x64 DiscretizeRegion[R] returns the result after 6m34s of work on my system (screenshot). $\endgroup$ Apr 19, 2016 at 0:40
  • 1
    $\begingroup$ Could you report this as a bug to Wolfram Research and add information on the case number they give to it? $\endgroup$
    – kirma
    Apr 19, 2016 at 3:58
  • $\begingroup$ I reported a bug to Wolfram and they opened CASE:3585657. They also said, that DiscretizeRegion can be sped up by specifying the Method to use (e.g. Boolean or RegionPlot), e.g. DiscretizeRegion[R, Method -> "RegionPlot"] . $\endgroup$
    – asmaier
    May 1, 2016 at 20:03

1 Answer 1

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Looks like you've uncovered a bug. I can confirm this behavior in 10.3.1 and 10.4. You can still discretize your region using DiscretizeGraphics though:

r = DiscretizeGraphics@
     RegionPlot[0 < Sin[u]/Cos[v] < 1 && 0 < Sin[v]/Cos[u] < 1, {u, 0, 2}, {v, 0, 2}]

Mathematica graphics

And if you want finer areas, use DiscretizeRegion:

DiscretizeRegion[r, MaxCellMeasure -> 0.001]

Mathematica graphics

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