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Opened 15 years ago

Last modified 15 years ago

#215 new defect

NaN values in replicated state produce continuous updates

Reported by: hauma Owned by: hauma
Priority: normal Milestone: 2.0
Component: uka.karo Version: 1.08a
Severity: normal Keywords:
Cc:

Description

The update mechanism used in CollectiveReplication only marshals updates form one replica to another, only if the actual value in one replica has changed. This test uses the built-in (==) operator for all primitive types. Since Double.NaN != Double.NaN, this test detects always an update for replicated float and double values that are NaN.

A side effect of this behavior is that NaN values are likely to dominate changes to replicas of such double or float variables. After some has set a variable to NaN, it is hard to override this in a collective update, because each rank generates an update for its NaN value.

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Change History (1)

comment:1 Changed 15 years ago by hauma

  • Milestone set to 2.00

Evaluation

Continuous updates for NaN values can be easily prevented by using a slightly more complex test for changes in float and double values using Double.isNaN(). But this would unnecessarily slow down the update for all floating point values. Since NaN is a strong evidence of a program error, its dominating behavior could even have advantages.

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