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        Dear all,
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                        In Gmsh, I have a test.geo file. The question is:
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                                        if I run <code style="margin:0px;padding:1px 5px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas, Menlo, Monaco, "font-size:13px;vertical-align:baseline;box-sizing:inherit;background-color:#EFF0F1;white-space:pre-wrap;">gmsh -3 test.geo</code> in the command line, I get the below error.
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<pre style="margin-top:0.5em;margin-bottom:1em;padding:5px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas, Menlo, Monaco, "font-size:13px;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto;background-color:#EFF0F1;word-wrap:normal;"><code style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas, Menlo, Monaco, "vertical-align:baseline;box-sizing:inherit;white-space:inherit;">Error   : Surface mesh is wrong, cannot do the 3D mesh
Info    : Done meshing 3D (0.002836 s)
Info    : 927 vertices 2064 elements
Error   : ------------------------------
Error   : Mesh generation error summary
Error   :     0 warnings
Error   :     2 errors
Error   : Check the full log for details
Error   : ------------------------------ </code></pre>
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                                        if I partition the <code style="margin:0px;padding:1px 5px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas, Menlo, Monaco, "font-size:13px;vertical-align:baseline;box-sizing:inherit;background-color:#EFF0F1;white-space:pre-wrap;">test.geo</code> in Gmsh GUI, sometimes I get the same error as above. But if I reload <code style="margin:0px;padding:1px 5px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas, Menlo, Monaco, "font-size:13px;vertical-align:baseline;box-sizing:inherit;background-color:#EFF0F1;white-space:pre-wrap;">test.geo</code> and then <code style="margin:0px;padding:1px 5px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas, Menlo, Monaco, "font-size:13px;vertical-align:baseline;box-sizing:inherit;background-color:#EFF0F1;white-space:pre-wrap;">3D</code> it many times, I am sure I can get the right 3-D partition.
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                        The <code style="margin:0px;padding:1px 5px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas, Menlo, Monaco, "font-size:13px;vertical-align:baseline;box-sizing:inherit;background-color:#EFF0F1;white-space:pre-wrap;">test.geo</code> file can be obtained from <a href="https://github.com/fanronghong/connect_local_github/blob/master/test.geo" rel="nofollow noreferrer" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;color:#18529A;">test.geo file</a>
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                        So how does this happen?
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