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Advanced question on iCustom function!

  • #1
  • First Post: Nov 25, 2019 3:23am Nov 25, 2019 3:23am
Hello, i have a quick (and painless, i hope) question about iCustom: let's say that i have 3 indicators called Ind_A, Ind_B and Ind_C, and i have an Expert Advisor called EA.
the EA calls all the 3 indicators using icustom, passing their arguments and getting the results by indexing their respctive buffers.
i attach my 3 indicator on the EURUSD chart and i run my EA; let's focus on the indicator Ind_A, he is running as indicator but at the same time is executed by the EA: the instance is the same or we have two instances of ind_A running? (i mean, one instance runs on his own and the other instance lives inside the EA).
in suche case, each instance has his own buffer? or is the buffer shared between all the instances of the indicator?
Many thanks!
  • #2
  • Nov 25, 2019 3:34am Nov 25, 2019 3:34am
Hi,

The iCustom function will create a separate instance of the indicator, which is unrelated to the same indicator on the chart or any other iCustom instance of it. Hope this helps.

Regards
  • #3
  • Nov 25, 2019 3:38am Nov 25, 2019 3:38am
Thank you so much!
but the buffers are shared in that case?
i mean the indicator called by the EA and the standalone indicator share the same buffer?
  • #4
  • Nov 25, 2019 3:47am Nov 25, 2019 3:47am
i believe they are independent. if the Inputs of the Ind_A and EA differ the EA will take its signals from the EA values for Ind_A.
  • #5
  • Nov 25, 2019 3:52am Nov 25, 2019 3:52am
Quoting stalkerMT4
but the buffers are shared in that case? i mean the indicator called by the EA and the standalone indicator share the same buffer?
The buffers are not shared, since you can have different inputs. You can easily test this.
  • #6
  • Nov 25, 2019 3:54am Nov 25, 2019 3:54am
ok, thanks to both!
  • #7
  • Nov 25, 2019 4:37am Nov 25, 2019 4:37am
i think it's different in MT5 though, because MT5 displays ALL the used indicators in the visual BT mode, but they share the same computations & buffers
  • #8
  • Nov 25, 2019 5:05am Nov 25, 2019 5:05am
Quoting ionone
i think it's different in MT5 though, because MT5 displays ALL the used indicators in the visual BT mode, but they share the same computations & buffers
my situation is a bit complex:
i have
Ind_A called every minute
Ind_B called at every tick
Ind_C called at every tick

the EA calls
Ind_A at every minute
Ind_B at every second and minute
Ind_C at every second and minute

and i have to convert this stuff in C# ehehehe

the indicators are well converted, i have doubts about the EA conversion
  • #9
  • Nov 25, 2019 6:51am Nov 25, 2019 6:51am
Quoting Wanderer272
Hi, The iCustom function will create a separate instance of the indicator, which is unrelated to the same indicator on the chart or any other iCustom instance of it. Hope this helps. Regards
@stalkerMT4:
Two calls of iCustom() accessing the same indicator operate on the same indicator instance (with shared indicator buffers) only then if both calls use the exact same parameters for symbol, timeframe and indicator parameters (not for the accessed buffer and bar). Furthermore for both calls using the same instance the specified indicator parameters must be of the exact same data type. This is true also for inputs completely unrelated to the indicator logic - like colors, line styles or string separators one may use to make the input dialog more user friendly.

You may want to add a Print() or debug statement to your Indicator::OnInit() function to always see in the log when a new instance is created. Opposite to regular indicator behaviour in charts an indicator loaded by iCustom() executes OnInit() only once and not on every chart change event. Again, you can easily see this with such debug statements.
It takes blood, sweat and enough tears to wash away the blood.
  • #10
  • Edited 8:01am Nov 25, 2019 7:33am | Edited 8:01am
hi emmzett, i don't have 2 calls to icustom, i have a call icustom for each indicators and i have the 3 indicators running on their own (once attached to the graph indeed).
  • #11
  • Nov 25, 2019 3:10pm Nov 25, 2019 3:10pm
Also, EA's do not create a buffer. check it out.
  • #12
  • Nov 25, 2019 10:40pm Nov 25, 2019 10:40pm
Quoting 240z
Also, EA's do not create a buffer. check it out.
Any iCustom call creates a buffer, how else is it going to calculate indicator values?
  • #13
  • Nov 26, 2019 2:24pm Nov 26, 2019 2:24pm
Quoting 240z
Also, EA's do not create a buffer. check it out.
i'll do: so actually the buffers are shared?
  • #14
  • Nov 28, 2019 6:56am Nov 28, 2019 6:56am
another question: the indicator called by icustom is active on events (int start)
Now, int start is equal to OnTick()... but how it works in that case?
my icustom is called each second, so also the indicator is called at each second: but it seems that the indicator is not active on each tick...
  • #15
  • Edited 7:28am Nov 28, 2019 7:17am | Edited 7:28am
Quoting stalkerMT4
another question: the indicator called by icustom is active on events (int start) Now, int start is equal to OnTick()... but how it works in that case? my icustom is called each second, so also the indicator is called at each second: but it seems that the indicator is not active on each tick...
An indicator called by iCustom() is not executed on every tick but on every call to iCustom(). It get's the latest price from the price queue (that is the latest tick) and calculates its values. If you call iCustom() on a M1 timeframe only - let's say - every 3 minutes, then the indicator behaves as if there was no tick for 2-3 minutes. It markes the last two bars as "changed" and calculates the current value using the latest tick. In your "for each bar { ... }" loop you have to calculate the last 3 bars and the actual tick. Exactly the same as if the indicator would be loaded onto a regular chart.

If you use int start() the correct indicator logic looks as follows. It re-calculates missed bars and updates the current bar with the latest tick:
Inserted Code
int start() {
   int periods = 200;
   int validBars = IndicatorCounted();
   int changedBars = Bars - validBars;
   // main loop
   for (int i=changedBars-1; i >= 0; i--) {
      buffer[i] = iMA(NULL, 0, 200,  0, MODE_SMA, PRICE_CLOSE, i);
   }
   return(0);
}
Forget about the loop examples provided by MetaQuotes and elsewhere on the net. Most of them are wrong. The above way is the correct way to calculate the start bar.

ps: You always have to re-calculate changed bars backwards (towards zero) to avoid indicator repainting. Not the other way around.
It takes blood, sweat and enough tears to wash away the blood.
  • #16
  • Nov 28, 2019 9:47am Nov 28, 2019 9:47am
thanks emmzett for the valuable informations! actually the indicator that i call is MBFX;
normally (i mean, when the indicator is attached to the graph) MBFX is called at each tick, but when is called by i custom, he gets the last tick only?
  • #17
  • Last Post: Nov 28, 2019 11:54am Nov 28, 2019 11:54am
Quoting stalkerMT4
thanks emmzett for the valuable informations! actually the indicator that i call is MBFX; normally (i mean, when the indicator is attached to the graph) MBFX is called at each tick, but when is called by i custom, he gets the last tick only?
Yes. It re-calculates everything missing since the last call of iCustom(). So nothing is lost evevn if not called on every tick.
It takes blood, sweat and enough tears to wash away the blood.
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