MT4 function for "hibernating" EA settings? | Forex Factory

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MT4 function for "hibernating" EA settings?

  • #1
  • First Post: Oct 2, 2010 6:31am Oct 2, 2010 6:31am
Anybody know if there's some code out there for "hibernating" (basically saving) the variables of a EA (typically to a file) so they can be re-loaded in case of a computer crashing or whatever? As far as I know MetaTrader will automatically save the internal state of an EA if the entire terminal is shut down but I don't think it does if the EA is accidently detached or the chart windows is accidently closed.
  • #2
  • Oct 2, 2010 7:18am Oct 2, 2010 7:18am
hey frinkfx..... not completely clear on just what your wanting to save and for how long but true global variables, those seen in the global variables list, will stay untill deleted, updated or time expiration.....


also can't remember exactly who but it was one of those that help out quite often like , sangmane, kenny hubard, codemiester, taiyakixz or someone else, had posted some reasons for denit code......

either one of those methods might save the variables......h
to trade and code, keep both simple... no call to impress....h
  • #3
  • Oct 2, 2010 8:30am Oct 2, 2010 8:30am
I'd rather leave the DeInit() alone as I want something that periodically saves the variables every tick so in case of a sudden power cut the EA can get back up and running and be in (as close to) the same state as it was before.

It's no problem, I just thought there might have been something out there that was already written that could save me the bother of writing it
  • #4
  • Edited 5:47pm Oct 2, 2010 9:26am | Edited 5:47pm
It depends on your EA what you want to save.

You should design your EA from the ground up so that it is able to restore everything from the existing trades and orders that it will find when starting up (after a crash) and maybe a few global variables. My global variables all have the magic number in their name so they cannot be confused with other instances. Magic number itself is created with a hash function.

For example I have an EA that will place many pending orders (similar to a grid EA) and also can have many trades open at a time and then there is a "level" which effectively means how many trades are already open, and some other things the EA needs to know before placing new orders. I do not rely on any of these information to be stored in variables that can get lost. For every such information (for example the current level number or the entry price of the oldest trade or the price for the next order, etc) I have spend a considerable time to design functions that are able to retrieve the information from nothing but the order list or global variables! Either I re-calculate them in init() or sometimes I even do this on the fly whenever I need them. (my previous profit for example is always directly read from a global whenever I need it in a calculation)

This is the most important design principle I apply to all my EAs: On init() it is able to recover and restore all needed information from nothing but the trade list and maybe only a handful of global variables that are stored immediately when they change. For example the total realized profit of all previous "cycles" to calculate the profit of the running "cycle" is stored in a global whenever it changes (I do not wait until deinit()). As my EAs evolve I test these things very thoroughly. I intentionally switch timeframes during operation, close the chart and reopen and reattach the EA and even intentionally crash and restart MT4 to make sure it can always fully recover and seamlessly continue where it left.

It might be complicated for some things but it is always worth the effort.
  • #5
  • Oct 2, 2010 12:00pm Oct 2, 2010 12:00pm
Thanks, 7bit. You sound like a true computer programmer. I think I'll just code something simple that saves the globals to a 'csv file every tick then re-loads them on restart. I don't need military grade programming as I'll only have the EA's running on my machine
  • #6
  • Edited 6:37pm Oct 2, 2010 6:02pm | Edited 6:37pm
Quoting FrinkFX
Thanks, 7bit. You sound like a true computer programmer. I think I'll just code something simple that saves the globals to a 'csv file every tick then re-loads them on restart. I don't need military grade programming as I'll only have the EA's running on my machine
You don't need to save everything on every tick, just save the variable if it changes. And make it more convenient by writing setters (and maybe also getters):

instead of this:
Inserted Code
int level

int start(){
   ...
   if (something) {
      [color=Red][b]level =[/b][/color] level + 1;
   }
   ...
   if (somethingelse) {
      [b][color=Red]level =[/color][/b] level - 1;
   }
use this:
Inserted Code
int level;

void [b][color=Red]SetLevel[/color][/b](int alevel){
   level = alevel;
   GlobalVariableSet("MyEa_level_" + magic, alevel);
}

int init(){
   ...
   level = GobalVariableGet("MyEa_level_" + magic");
}

int start(){
   ...
   if (something) {
      [color=Red][b]SetLevel[/b][/color](level + 1);
   }
   ...
   if (somethingelse) {
      [b][color=Red]SetLevel[/color][/b](level - 1);
   }
Now you have made sure that whenever you change the level it will immediately saved to disk (MT4 saves this always to disk) if you replace every occurrence of "level =" with "SetLevel()". You could also make a function GetLevel() and completely eliminate the need for the global "int level" variable declaration and only access it through Getlevel() and SetLevel() from now on:

Inserted Code
void [b][color=Red]SetLevel[/color][/b](int alevel){
   GlobalVariableSet("MyEa_level_" + magic, alevel);
}
 
int [color=SeaGreen][b]GetLevel[/b][/color](){
   return(GlobalVariableGet("MyEa_level_" + magic));
}

[color=Gray]// no global[b] int level[/b] and also
// no initializing in init() anymore
// access it only through [b]getter[/b] and [b]setter[/b] functions!
[/color]
int start(){
   ...
   if (something) {
      [color=Red][b]SetLevel[/b][/color]([b][color=SeaGreen]GetLevel[/color][/b]() + 1);
   }
   ...
   if (somethingelse) {
      [b][color=Red]SetLevel[/color][/b]([color=SeaGreen][b]GetLevel[/b][/color]() - 1);
   }
For just saving some numeric values like a level number, a price, a time or a counter you can always use GlobalVariableSet() for saving them and GlobalVariableGet() to get them back. This is very easy, no need for messing around with file functions and they will survive any crash because MT4 will always save them to disk immediately.
  • #7
  • Oct 2, 2010 10:51pm Oct 2, 2010 10:51pm
That makes a lot of sense, I never knew about those GlobalVariableXXX functions. Gotta check em out.

Nice work
  • #8
  • Last Post: Oct 3, 2010 5:09am Oct 3, 2010 5:09am
Quoting FrinkFX
That makes a lot of sense, I never knew about those GlobalVariableXXX functions. Gotta check em out.

Nice work
You can also open a window in metatrader from the main menu to edit them directly. And if you hold a global EA variable completely in MT4 global variables like shown in my example you can easily check its value or even modify it (if necessary or for debugging purposes) while the EA is running.
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