0031849: Modeling Algorithms - Boolean operations produce different results on different systems

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Date Submitted

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0031849

Community

[OCCT] OCCT:Modeling Algorithms

public

2020-10-13 16:29

2020-10-14 10:58

Reporter

Matthias

Assigned To

msv

Priority

normal

Severity

minor

Status

new

Resolution

open

Platform

Windows

VC++ 2015

OS Version

64 bit

Product Version

[OCCT] 7.4.0

Target Version

[OCCT] 7.6.0*

Fixed in Version

Summary

0031849: Modeling Algorithms - Boolean operations produce different results on different systems

Description

We 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

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Test case number

Attached Files

res_skylake.brep (211,232 bytes) 2020-10-13 16:29

res_ivybridge.brep (211,242 bytes) 2020-10-13 16:29

s1.brep (22,573 bytes) 2020-10-13 16:29

s2.brep (44,272 bytes) 2020-10-13 16:29

fds_ivybridge.brep (2,050,190 bytes) 2020-10-14 09:59

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