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IDProjectCategoryView StatusDate SubmittedLast Update
0031849Community[OCCT] OCCT:Modeling Algorithmspublic2020-10-13 16:292020-10-14 10:58
ReporterMatthias 
Assigned Tomsv 
PrioritynormalSeverityminor 
StatusnewResolutionopen 
PlatformWindowsOSVC++ 2015OS Version64 bit
Product Version[OCCT] 7.4.0 
Target Version[OCCT] 7.6.0*Fixed in Version 
Summary0031849: Modeling Algorithms - Boolean operations produce different results on different systems
DescriptionWe encountered slightly different results of geometry generation processes being performed on systems with different processor architecture (Ivy bridge vs. Skylake, Zen2 etc.).

Attached are our resulting breps produced by DRAW script below (res_skylake.brep and res_ivybridge.brep).

1) Can you confirm these different results?
2) Can you provide some details for this different behavior?
Steps To Reproduce
pload ALL
datadir c:/temp
restore s1.brep
restore s2.brep
bsection res s1 s2
save res res.brep
TagsNo tags attached.
Test case number
Attached Files? file icon res_skylake.brep (211,232 bytes) 2020-10-13 16:29
? file icon res_ivybridge.brep (211,242 bytes) 2020-10-13 16:29
? file icon s1.brep (22,573 bytes) 2020-10-13 16:29
? file icon s2.brep (44,272 bytes) 2020-10-13 16:29
? file icon fds_ivybridge.brep (2,050,190 bytes) 2020-10-14 09:59
? file icon fds_skylake.brep (2,005,540 bytes) 2020-10-14 09:59

- Relationships

-  Notes
(0095941)
msv (developer)
2020-10-13 17:52

The difference is not greater than in 11th digit in double precision values. I think it can be explained by different numeric processors on different platforms. It is hardly possible to fix this problem.
(0095952)
Matthias (developer)
2020-10-14 09:58

You are right, but these differences increase with ongoing manipulations of the model.

We got aware of it when a (seemingly valid) shape produced on Ivybridge architecture could not be meshed on any platform using CADExchanger SDK (which is going to be investigated).

For the sake of completeness, the shapes are attached (fds_ivybridge.brep, fds_skylake.brep).
(0095955)
msv (developer)
2020-10-14 10:58

Both shapes are meshed with no problems using OCCT BRepMesh algorithm.

- Issue History
Date Modified Username Field Change
2020-10-13 16:29 Matthias New Issue
2020-10-13 16:29 Matthias Assigned To => bugmaster
2020-10-13 16:29 Matthias File Added: res_skylake.brep
2020-10-13 16:29 Matthias File Added: res_ivybridge.brep
2020-10-13 16:29 Matthias File Added: s1.brep
2020-10-13 16:29 Matthias File Added: s2.brep
2020-10-13 17:02 kgv Assigned To bugmaster => msv
2020-10-13 17:02 kgv Summary Boolean operations produce different results on different systems => Modeling Algorithms - Boolean operations produce different results on different systems
2020-10-13 17:02 kgv Steps to Reproduce Updated View Revisions
2020-10-13 17:52 msv Note Added: 0095941
2020-10-14 09:58 Matthias Note Added: 0095952
2020-10-14 09:59 Matthias File Added: fds_ivybridge.brep
2020-10-14 09:59 Matthias File Added: fds_skylake.brep
2020-10-14 10:58 msv Note Added: 0095955


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