CODEWITHSUNDEEP
javascriptarraysmultithreadingobjectparallel-processing
Henry
Henry

Reputation: 421

How to edit objects attributes from array using parallel/multithreading Hamsters.js Javascript lib

When using Hamster.js we have to define the parameter array as params = {"array":my_array}

my_array is formed by elements with many attributes and I need to change the attributes x and y.

In the function I pass to Hamster.js I defined:

function map_node_hamster() {
        params.array.forEach(function (d) {
            d.x = some_calculation_here;           
            d.y = other_calculation_here;
        }
}

but after calling the hamster.run() function, the elements of my original array stay intact. As I need performance, I thought Hamsters could just change the values that my array is pointing. I actually do not know much about Javascript and how it manages arrays.

I'm calling the run function like this:

console.log("Before hamster:");
console.log(network.nodes);

p = {'array': network.nodes, "w": w, "h":h};

hamsters.run(p, map_node_hamster, function(output){console.log(output); return output;}, hamsters.maxThreads, true);

console.log("After hamster:");
console.log(network.nodes);

And the elements of network.nodes are intact after hamsters.run().

How could I change elements of array inside run function? Or.. How would be the right way to do the changes?

As the vector nodes is large, copying, sorting, and things like this will decrease performance and maybe it will be worst than single thread/non-parallel version.

Upvotes: 0

Views: 324

Answers (1)

Henry
Henry

Reputation: 421

It seems like the answer is to create an index array and change nodes in the callback function (output).

Despite the behavior of my "d3 graphic representation of network" is really not what I expected... maybe the code is actually right in the sense of answering my question (how to change objects from array in parallel computing with Hamsters.js). That is:

            p = {'array': network.indexes,
                "nodes": network.nodes,                
                "w": w,
                "h": h};
            hamsters.run(p, map_node_hamster, function (output) {
                output.forEach(function (d) {
                    network.nodes[d.i].x = d.xy[0];
                    network.nodes[d.i].y = d.xy[1];
                });
                return output;
            }, cores, true);

And... changing the function to work like this:

function map_node_hamster() {
        pfor (var i = 0; i < params.array.length; i++) {
            var result;
            var d = params.nodes[params.array[i]];
            var d = params.nodes[params.array[i]];
            result = {x: d.x calculation, y: d.y calculation};
            rtn.data.push({"i": params.array[i], "xy": [result.x, result.y]});
        }
}

Upvotes: 0

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