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map
myParallelArray.map(elementalFunction, arg1, arg2, ...)
elementalFunction described below
arg1, arg2, ... optional arguments passed unchanged to elemental function
function (val, arg1, arg2, ...) { <body of the function> }
this Inside the body of the elemental function, the value of this is the ParallelArray object on which the map was invoked - for example, in the invocation of map above, the this would refer to myParallelArray
val An element from the ParallelArray
arg1, arg2, ... - Same as the optional arguments passed to map.
The result of the function will be used as an element to be placed in the result at the same offset we found val in the source array.
A freshly minted ParallelArray
Elements are the results of applying the elemental function to the elements in the original ParallelArray plus any optional arguments.
Unlike combine, map does not provide a depth argument to steer the number of dimensions the map operation iterates over. Instead, flatten can be used to collapse the outer dimensions of an array into a single dimension. A consecutive application of map then iterates over all previously collapsed dimensions. Finally, partition can be used to restore the original shape of the array. For example, instead of
result = pa.map(2, f);
where 2 would be the depth argument, can instead be expressed by
tmp = pa.flatten();
tmp = tmp.map(f);
result = tmp.partition(pa.getShape()[0]);
Note that this does not work for combine. As combine exposes the iteration index to the elemental function, collapsing the iteration space to a single index would be observable from the elemental function.
// an identity function
pa.map(function(val){return val;})
// Adding one to each element.
var source = new ParallelArray([1,2,3,4,5]);
var plusOne = source.map(function inc(v) { return v+1; }); //<2,3,4,5,6>