It is out of our control to save data consistently. The only thing we can do is to use old "architecture" cause it is not as buggy as new one.

It does not work because nodes the game world is simulated on do not see the same data at the same time. In simple words, data are inconsistent.

Optimized a bit:
average CPU consumption: 11.64
average creep count: 55.88
number of rooms: 5
CPU limit: 20

Can somebody explain me why does a script containing the single line
console.log(Game.cpuLimit);
output the following:

[10:45:31 AM] 261
[10:45:44 AM] 281 // ok, +20 (CPU limit is set to 20)
[10:46:08 AM] 279 // strange, -2
[10:46:15 AM] 296 // basically, ok, +17
[10:46:27 AM] 313
[10:46:31 AM] 328
[10:46:39 AM] 289 // very strange, -39
[10:46:44 AM] 308
[10:46:56 AM] 325
[10:47:01 AM] 325 // strange, 0
[10:47:12 AM] 341
[10:47:25 AM] 360
[10:47:37 AM] 380
[10:47:48 AM] 399
[10:48:01 AM] 418
[10:48:13 AM] 418 // 0 again

Yesterday the length of a tick was about 3 seconds. At the moment one tick is simulated in 10 seconds. Where the world is heading...

average CPU consumption: 14.77
average creep count: 45.24
number of rooms: 4
CPU limit: 20

I want to optimize my code but do not have enough time

Having 2 energy sources in the room you can upgrade the controller up to level 4 until walls down.

You can predefine levels for every role as follows:

var carrier_levels = [ { cost: 100, body: [ CARRY, MOVE ] }, { cost: 200, body: [ CARRY, MOVE, CARRY, MOVE ] } ];

Then select most appropriate level for certain conditions.

Disclaimer: I did not program with javascript until started playing screeps.

Recently my script has been terminated due to CPU limit. In order to deal with this issue I wrote the following code:

var enable_profiling = true;
if (enable_profiling) {
    Memory.p = Memory.p || {};

    var wrap = function(c, n) {
        var p = Memory.p[n] || { usage: 0, count: 0 };
        Memory.p[n] = p;

        var f = c.prototype[n];
        c.prototype[n] = function() {
            var ts = Game.getUsedCpu();
            var rc = f.apply(this, arguments);
            p.usage += Game.getUsedCpu() - ts;
            ++p.count;
            return rc;
        };
    };

    wrap(RoomPosition, 'isNearTo');
    wrap(RoomPosition, 'findPathTo');
    wrap(RoomPosition, 'isEqualTo');
    wrap(RoomPosition, 'findClosest');
    wrap(Creep, 'moveByPath');
    wrap(Creep, 'moveTo');
    wrap(Creep, 'pickup');
    wrap(Creep, 'build');
    wrap(Creep, 'repair');
    wrap(Creep, 'harvest');
    wrap(Creep, 'upgradeController');
    wrap(Room, 'lookForAt');
    wrap(Room, 'find');
    wrap(Spawn, 'createCreep');
}

....   // main code

var report_interval = 200;
if (Game.time % report_interval == 0) {
        var summary = 0;
        for (var n in Memory.p) {
            var p = Memory.p[n];
            if (p.count === 0) {
                p.average = 0;
                continue;
            }
            p.average = p.usage / p.count;
            summary += p.average;
        }

        for (var n in Memory.p) {
            var p = Memory.p[n];
            console.log(n + ': ' + p.usage.toFixed(2) + '/' + p.count + ' == ' + p.average.toFixed(2)
                        + ' (' + (p.average * 100 / summary).toFixed(2) + '%)');
        }
        console.log('--- ' + summary.toFixed(2));

        Memory.p = {};
}

Feel free to use it.

chris, probably not. I have slightly optimized the search function by caching neighbors for traversed points. The cache is gone after leaving the function.