Below are the functions I have written:
map:
function () {
// initialize KEY
// initialize INDEX (0..65536)
// initialize VALUE
var arr = [];
arr[INDEX] = { val: VALUE, count: 1 };
emit(KEY, { arr: arr });
}
reduce:
function (key, values) {
var result = { arr: [] };
for (var i = 0; i < values.length; i++) {
values[i].arr.forEach(function (item, i) {
if (result.arr.hasOwnProperty(i)) {
result.arr[i].val += item.val;
result.arr[i].count += item.count ;
} else {
result.arr[i] = item;
}
});
}
It seems that when transferring the associative array from map to reduce, there is an issue in enumerating the values of the array. This results in having to deal with undefined elements during each reduce operation.
Interestingly, enumerating the array (arr) within map produces the expected outcome with only defined elements.
I am now questioning whether an associative array is the most efficient solution for my task. Is there a faster way to find elements based on ID?
I would appreciate your insights on the following:
What causes the differences in array processing between the map and reduce functions?
Which data structure should I consider using (or how can I optimize my current array usage) to improve the efficiency of my solution?