A play with permutations

permutations.js

var _ = require("underscore");

var array_size = 4;
var iterations = 200000000;

var get_array = function () {
    var a = [];

    for (var i = 0; i < array_size; i++) {
        a.push(i);
    }

    return a
}

all_swaps_results = {};
half_swaps_results = {};
half_swaps_original_picked_randomly_results = {};

var random_numbers_picked = {}
for (var i = 0; i < array_size; i++) {
    random_numbers_picked[i] = 0;
}

var target, swap, subject;
while (iterations !== 0) {
    subject = get_array();
    for (var i = 0; i < array_size; i++) {
        target = (parseInt(Math.random() * 100000) % array_size);

        swap = subject[target];
        subject[target] = subject[i];
        subject[i] = swap;

        random_numbers_picked[target] += 1;
    }

    if (typeof all_swaps_results[subject.join("|")] !== 'undefined') {
        all_swaps_results[subject.join("|")] += 1;
    } else {
        all_swaps_results[subject.join("|")] = 1;
    }

    subject = get_array();
    for (var i = 0; i < Math.ceil(array_size / 2); i++) {
        target = (parseInt(Math.random() * 100000) % array_size);

        swap = subject[target];
        subject[target] = subject[i];
        subject[i] = swap;

        random_numbers_picked[target] += 1;
    }

    if (typeof half_swaps_results[subject.join("|")] !== 'undefined') {
        half_swaps_results[subject.join("|")] += 1;
    } else {
        half_swaps_results[subject.join("|")] = 1;
    }

    subject = get_array();
    for (var i = 0; i < Math.ceil(array_size / 2); i++) {
        origin = (parseInt(Math.random() * 100000) % array_size);
        target = (parseInt(Math.random() * 100000) % array_size);

        swap = subject[target];
        subject[target] = subject[origin];
        subject[origin] = swap;

        random_numbers_picked[origin] += 1;
        random_numbers_picked[target] += 1;
    }

    if (typeof half_swaps_original_picked_randomly_results[subject.join("|")] !== 'undefined') {
        half_swaps_original_picked_randomly_results[subject.join("|")] += 1;
    } else {
        half_swaps_original_picked_randomly_results[subject.join("|")] = 1;
    }

    if (iterations % 1000000 === 0) {
        console.log(iterations, _.size(random_numbers_picked), _.size(all_swaps_results), _.size(half_swaps_results), _.size(half_swaps_original_picked_randomly_results));
        console.log(iterations, random_numbers_picked, all_swaps_results, half_swaps_results, half_swaps_original_picked_randomly_results);
    }
    iterations--;
}

console.log(iterations, _.size(random_numbers_picked), _.size(all_swaps_results), _.size(half_swaps_results), _.size(half_swaps_original_picked_randomly_results));
console.log(iterations, random_numbers_picked, all_swaps_results, half_swaps_results, half_swaps_original_picked_randomly_results);