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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>Hello<o:p></o:p></p><p class=MsoNormal>I am using DMPlex to construct a fully circular 2D domain for my PDEs. As I am discretizing the PDEs using finite difference method, I need to know , to define the layout of PetscSection, how I can find the boundary condition IS. I know the location of the boundaries in Sieve chart. However, I noticed that I need to know the Index Set of that location. Can I use the Sieve point number for Index Set. It seems I think I am not familiar with IS. Can you help me? Thank for your help. <o:p></o:p></p><p class=MsoNormal>Amir<o:p></o:p></p></div></body></html>