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I have an array named globalArrayAllTrades as you see below. I simply like to INVERT the date in a new copy of the array. So I loop through, create a new object and add it to the new array - simple.

Then function does exactly as expected. BUT if the array contains too many objects the code fails with a "FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - process out of memory".

My laptop has 8 GB of memory...When the NODEJS process crashes it uses about 1.5 GB and about 70% of of totally amount of available memory is used.

I do run the NODEJS app with the parameter: --max_old_space_size=5000 which normally fixes every thing. But not this one and i have tried MANY different ways to code the same function - BUT each and every time - it fails...unless the original array is smaller.

How can I fix this issue? 

 function invertTrades(){

     var original = globalArrayAllTrades.slice();

     globalArrayAllTrades.length = 0;
     globalListAllTrades.length = 0;

     for(var i = 0; i < original.length; i++){

         var objS = original[i];
         var objE = original[original.length-1-i];
         var objInv = new TradePoint(objS.number, objS.matchdate, objE.price, objE.size, objE.issell);

         globalArrayAllTrades.push(objInv);

         globalListAllTrades[objInv.matchdate] = objInv;
     }
 }
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8
  • This may answer: stackoverflow.com/questions/7193959/… Commented Nov 11, 2016 at 0:05
  • @Simon That question is 5 years old. One of the answers says that the memory limit has been removed. Commented Nov 11, 2016 at 0:09
  • What is globalListAllTrades? It seems like you're using it as a key-value-store (object), so .length = 0 will hardly empty it. Commented Nov 11, 2016 at 0:12
  • @Bergi You're right, that doesn't do anything, but I don't think it matters. He's replacing all the entries with globalListAllTrades[objInv.matchdate] = objInv. Commented Nov 11, 2016 at 0:13
  • Does the TradePoint constructor have any side effects? Why are you making that original copy? Where is globalArrayAllTrades declared? How large is it (what is original.length)? Commented Nov 11, 2016 at 0:13

3 Answers 3

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You can save some memory by making original just contain the properties you need to invert, not the whole TradePoint object. Then you don't need to construct new TradePoint objects, you can modify them in place.

var original = globalArrayAllTrades.map(function(trade) {
    return {
        trade.price,
        trade.size,
        trade.issell
    };
}).reverse();
globalArrayAllTrades.forEach(function(trade, i) {
    trade.price = original[i].price;
    trade.size = original[i].size;
    trade.issell = original[i].issell;
});

And since all the objects were modified in place, there's no need to update globalListAllTrades.

Another way is to swap the price, size, and issell properties in place between the pairs of elements:

var midpoint = Math.floor(globalArrayAllTrade.length/2);
for (var i = 0; i < midpoint; i++) {
    var objS = globalArrayAllTrades[i];
    var objE = globalArrayAllTrades[globalArrayAllTrades.length-1-i];

    var temp = objS.price;
    objS.price = objE.price;
    objE.price = temp;

    temp = objS.size;
    objS.size = objE.size;
    objE.size = temp;

    temp = objS.issell;
    objS.issell = objE.issell;
    objE.issell = temp;
}
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14 Comments

I don't know this notation... what is trade? Anyways... i think this solution will use more memory than Bergi's ...and that still fails...
trade is the current element of the array in the .forEach() loop.
I added another solution that doesn't allocate any new memory, it swaps the properties in place.
The first one - failed.
Second one. I get your point! But god damn. It still crashes!?
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Have you considered just doing this?

// Copy array and then reverse it
var newArray = [].concat(original).reverse();

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reverse

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2 Comments

he's not just reversing the array. He's combining properties of the objects opposite each other in the array. Look at objInv.
Its NOT ALL properties in the array i like to change! The date must be the same - but price and the rest - must be "invert".
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I would suggest avoiding to copy that array:

function getInverse(i) {
    var objS = globalArrayAllTrades[i];
    var objE = globalArrayAllTrades[globalArrayAllTrades.length-1-i];
    var objInv = new TradePoint(objS.number, objS.matchdate, objE.price, objE.size, objE.issell);
    globalListAllTrades[objInv.matchdate] = objInv;
    return objInv;
}
function invertTrades(){
     globalListAllTrades.length = 0;
     for (var i = 0, l = Math.floor(globalArrayAllTrades.length/2); i < l; i++) {
         var j = globalArrayAllTrades.length-1-i;
         var a = getInverse(i);
         var b = getInverse(j);
         globalArrayAllTrades[i] = a;
         globalArrayAllTrades[j] = b;
     }
 }
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4 Comments

Really nice try! Smart. But i must disappoint you. It still crashes.
globalArrayAllTrades/2 should be globalArrayAllTrades.length/2
Hmm, that won't work because you set globalListAllTrades.length = 0 on the line before. You need to get the midpoint before you do that.
@Barmar That's globalList… not globalArray…. It might be omitted nonetheless, though.

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