Scatter-Gather Iteration aggregators

[Lydia Ickler]

Hi,

I have a question regarding the Aggregators of a Scatter-Gather Iteration.

Is it possible to have a global aggregator that is accessible in VertexUpdateFunction() and MessagingFunction() at the same time?

Thanks in advance,

Lydia

[Vasiliki Kalavri]

Hi Lydia,

registered aggregators through the ScatterGatherConfiguration are accessible both in the VertexUpdateFunction and in the MessageFunction.

Cheers,

-Vasia.

On 12 May 2016 at 20:08, Lydia Ickler <[hidden email]> wrote:

Hi,

I have a question regarding the Aggregators of a Scatter-Gather Iteration.

Is it possible to have a global aggregator that is accessible in VertexUpdateFunction() and MessagingFunction() at the same time?

Thanks in advance,

Lydia

[Lydia Ickler]

Hi Vasia, 

yes, but only independently within each Function or not?

If I set the aggregator in VertexUpdateFunction then the newly set value is not visible in the MessageFunction.

Or am I doing something wrong? I would like to have a shared aggregator to normalize vertices.

Am 13.05.2016 um 08:04 schrieb Vasiliki Kalavri <[hidden email]>:

Hi Lydia,

registered aggregators through the ScatterGatherConfiguration are accessible both in the VertexUpdateFunction and in the MessageFunction.

Cheers,

-Vasia.

On 12 May 2016 at 20:08, Lydia Ickler <[hidden email]> wrote:

Hi,

I have a question regarding the Aggregators of a Scatter-Gather Iteration.

Is it possible to have a global aggregator that is accessible in VertexUpdateFunction() and MessagingFunction() at the same time?

Thanks in advance,

Lydia

[Vasiliki Kalavri]

Hi Lydia, 

an iteration aggregator combines all aggregates globally once per superstep and makes them available in the *next* superstep.

Within each scatter-gather iteration, one MessagingFunction (scatter phase) and one VertexUpdateFunction (gather phase) are executed. Thus, if you set an aggregate value within one of those, the value will be available in the next superstep. You can retrieve it calling the getPreviousIterationAggregate() method.

Let me know if that clears things up!

-Vasia.

On 13 May 2016 at 08:57, Lydia Ickler <[hidden email]> wrote:

Hi Vasia, 

yes, but only independently within each Function or not?

If I set the aggregator in VertexUpdateFunction then the newly set value is not visible in the MessageFunction.

Or am I doing something wrong? I would like to have a shared aggregator to normalize vertices.

Am 13.05.2016 um 08:04 schrieb Vasiliki Kalavri <[hidden email]>:

Hi Lydia,

registered aggregators through the ScatterGatherConfiguration are accessible both in the VertexUpdateFunction and in the MessageFunction.

Cheers,

-Vasia.

On 12 May 2016 at 20:08, Lydia Ickler <[hidden email]> wrote:

Hi,

I have a question regarding the Aggregators of a Scatter-Gather Iteration.

Is it possible to have a global aggregator that is accessible in VertexUpdateFunction() and MessagingFunction() at the same time?

Thanks in advance,

Lydia

[Lydia Ickler]

Hi Vasia, 

okay I understand now :)

So it works fine if I want to collect the sum of values.

But what if I need to reset the DoubleSumAggregator back to 0 in order to then set it to a new value to save the absolute maximum?

Please have a look at the code above. 

Any idea why it is not working?

 

public static class VertexDistanceUpdater extends VertexUpdateFunction<Integer, Double, Double> {

    DoubleSumAggregator aggregator = new DoubleSumAggregator();

    public void preSuperstep() {
        // retrieve the Aggregator
        aggregator = getIterationAggregator("sumAggregator");
    }

    public void updateVertex(Vertex<Integer, Double> vertex, MessageIterator<Double> inMessages) {
        double sum = 0;
        for (double msg : inMessages) {
                sum = sum + (msg);
        }

        if((Math.abs(sum) > Math.abs(aggregator.getAggregate().getValue()))){

            aggregator.reset();
            aggregator.aggregate(sum);

        }
        setNewVertexValue(sum);
    }
}

Am 13.05.2016 um 09:25 schrieb Vasiliki Kalavri <[hidden email]>:

Hi Lydia, 

an iteration aggregator combines all aggregates globally once per superstep and makes them available in the *next* superstep.

Within each scatter-gather iteration, one MessagingFunction (scatter phase) and one VertexUpdateFunction (gather phase) are executed. Thus, if you set an aggregate value within one of those, the value will be available in the next superstep. You can retrieve it calling the getPreviousIterationAggregate() method.

Let me know if that clears things up!

-Vasia.

On 13 May 2016 at 08:57, Lydia Ickler <[hidden email]> wrote:

Hi Vasia, 

yes, but only independently within each Function or not?

If I set the aggregator in VertexUpdateFunction then the newly set value is not visible in the MessageFunction.

Or am I doing something wrong? I would like to have a shared aggregator to normalize vertices.

Am 13.05.2016 um 08:04 schrieb Vasiliki Kalavri <[hidden email]>:

Hi Lydia,

registered aggregators through the ScatterGatherConfiguration are accessible both in the VertexUpdateFunction and in the MessageFunction.

Cheers,

-Vasia.

On 12 May 2016 at 20:08, Lydia Ickler <[hidden email]> wrote:

Hi,

I have a question regarding the Aggregators of a Scatter-Gather Iteration.

Is it possible to have a global aggregator that is accessible in VertexUpdateFunction() and MessagingFunction() at the same time?

Thanks in advance,

Lydia

[Vasiliki Kalavri]

Hi Lydia,

aggregators are automatically reset at the beginning of each iteration. As far as I know, the reset() method is not supposed to be called from user code. Also, in the code you pasted, you use "aggregator.getAggregate()". Please, use the "getPreviousIterationAggregate()" method as I wrote above, otherwise you won't get the correct value.

Cheers,

-Vasia.

On 13 May 2016 at 11:03, Lydia Ickler <[hidden email]> wrote:

Hi Vasia, 

okay I understand now :)

So it works fine if I want to collect the sum of values.

But what if I need to reset the DoubleSumAggregator back to 0 in order to then set it to a new value to save the absolute maximum?

Please have a look at the code above. 

Any idea why it is not working?

 

public static class VertexDistanceUpdater extends VertexUpdateFunction<Integer, Double, Double> {

    DoubleSumAggregator aggregator = new DoubleSumAggregator();

    public void preSuperstep() {
        // retrieve the Aggregator
        aggregator = getIterationAggregator("sumAggregator");
    }

    public void updateVertex(Vertex<Integer, Double> vertex, MessageIterator<Double> inMessages) {
        double sum = 0;
        for (double msg : inMessages) {
                sum = sum + (msg);
        }

        if((Math.abs(sum) > Math.abs(aggregator.getAggregate().getValue()))){

            aggregator.reset();
            aggregator.aggregate(sum);

        }
        setNewVertexValue(sum);
    }
}

Am 13.05.2016 um 09:25 schrieb Vasiliki Kalavri <[hidden email]>:

Hi Lydia, 

an iteration aggregator combines all aggregates globally once per superstep and makes them available in the *next* superstep.

Within each scatter-gather iteration, one MessagingFunction (scatter phase) and one VertexUpdateFunction (gather phase) are executed. Thus, if you set an aggregate value within one of those, the value will be available in the next superstep. You can retrieve it calling the getPreviousIterationAggregate() method.

Let me know if that clears things up!

-Vasia.

On 13 May 2016 at 08:57, Lydia Ickler <[hidden email]> wrote:

Hi Vasia, 

yes, but only independently within each Function or not?

If I set the aggregator in VertexUpdateFunction then the newly set value is not visible in the MessageFunction.

Or am I doing something wrong? I would like to have a shared aggregator to normalize vertices.

Am 13.05.2016 um 08:04 schrieb Vasiliki Kalavri <[hidden email]>:

Hi Lydia,

registered aggregators through the ScatterGatherConfiguration are accessible both in the VertexUpdateFunction and in the MessageFunction.

Cheers,

-Vasia.

On 12 May 2016 at 20:08, Lydia Ickler <[hidden email]> wrote:

Hi,

I have a question regarding the Aggregators of a Scatter-Gather Iteration.

Is it possible to have a global aggregator that is accessible in VertexUpdateFunction() and MessagingFunction() at the same time?

Thanks in advance,

Lydia