Re: [jgrapht-users] Bizarre issue with TopologicalOrderIterator

[Alexander H. <ale...@my...>]

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The DAG internally uses HashSets/Maps to store vertices and edges,
these cause the non determinism when iterating, so it is nothing you
do :) Basically anything you compute by iterating over items in the
set (or the key in the map) is non deterministic.
The TopolOrderIterator uses these operations to compute the order, so
it is non deterministic.

Alex

On 12/04/2014 03:43 PM, org...@io... wrote:
>> On 2014-12-04T14:02:52 +0100 Alexander Herz
>> <ale...@my...> wrote:
>> 
>> That is java for you, data structures using hashes often use the
>> value of references to compute the hash. Since the pointer values
>> may change every run, the order things are iterated over may
>> change every run (there is no guarantee that the n-th call to
>> malloc in an application always yields the same address). In
>> order to make your application deterministic and debugable you
>> want to use LinkedHash.. data structures. These guarantee
>> deterministic behaviour (in single threaded execution).
> 
> Is this the case with the TopologicalOrderIterator (or the 
> DirectAcyclicGraph)?
> 
> I only use structural equality and hashes derived from values, as 
> opposed to reference equality or Object.hashCode() in my own code.
> 
> M
> 
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