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static variable accumulation on open

  • #1
  • First Post: Sep 20, 2007 2:54pm Sep 20, 2007 2:54pm
I want to accumulated a static variable but only once per bar. My problem is that it gets re-added on every tick when I only want to run the calculation once per bar on the very first tick.

A user on another forum posted this solution:
if(myTime != Time[0])
{
//do what you want to be done once after openning new bar

myTime = Time[0];
}

But I'm finding it works is some situations but not all and I can't find the reason for the discrepancy. Anyone know of a better way of doing this?
  • #2
  • Sep 20, 2007 3:26pm Sep 20, 2007 3:26pm
maybe try
PHP Code
if(TimeCurrent() == Time[0]){
//this gets executed when the last bar opens
}
  • #3
  • Sep 20, 2007 3:29pm Sep 20, 2007 3:29pm
Thanks for the reply but it doesn't seem to work.
  • #4
  • Sep 13, 2008 1:40pm Sep 13, 2008 1:40pm
You didn't say how you initialized your variable "myTime". If it was outside of start (i.e. global variable), you maybe tried "datetime myTime = 0;". If it was inside of start(), perhaps you did "static datetime myTime;". A 3rd alternative could have been you tried the static method as a global variable.

Any of these methods looks like it should have worked to me, but yet you say you have problems with your code sometimes not working. Hmmm...


I have little experience with static variables, but it seems to me instead of reference Time[0], you could try:


start()
{

static int last_countedBars;

int countedBars = IndicatorCounted();

if (last_countedBars != countedBars)
{
// do your unique once-per-bar commands here, including this line:
last_countedBars = countedBars;
...
} //end of if

} //end of start


I assume you are looking to take actions for the first tick of an actual bar that gets formed, as opposed to missing bars because there wasn't any tick to form a bar. Lots of M1/M5/... bars go "missing" during periods of inactivity.

Also note that if you start MT4 or change timeframes, the first tick it processes is unlikely to be the actual first tick of the bar. Only subsequent bars would process the first tick.

It's also possible that the program is still processing a tick for a previous bar when the 1st tick of the new bar occurs. If that happens, MT4 continues to process the last tick through the entire start() routine until finished, and only after that will it look for any subsequent tick in the new bar. You might have missed the 1st (or more) tick(s) that occurred while it was still busy. Perhaps this is the real answer to your problem. Sorry I don't know of a solution. You might be able to do an "IndicatatorCounted" at the very end of your start() block, and see if it incremented during your tick. MT4 talks about a "fringe" case with this command, and this might be it. I have no idea whether this method would help you or not.

MetaEditor says this:
Quote
int IndicatorCounted()The function returns the amount of bars not changed after the indicator had been launched last. The most calculated bars do not need any recalculation. In most cases, same count of index values do not need for recalculation. The function is used to optimize calculating.

Note: The latest bar is not considered to be calculated and, in the most cases, it is necessary to recalculate only this bar. However, there occur some boundary cases where custom indicator is called from the expert at the first tick of the new bar. It is possible that the last tick of the previous bar had not been processed (because the last-but-one tick was being processed when this last tick came), the custom indicator was not called and it was not calculated because of this. To avoid indicator calculation errors in such situations, the IndicatorCounted() function returns the count of bars minus one.

I'm not going to wrap my brain around this enough to figure it out, but it seems to read that IndicatorCounted cannot change during the processing of the start() routine, so looking for a change from beginning to end won't occur. But what about "Bars"?? and "Time[0]"?? Maybe those can and do indeed change meaning during your start block?! Give it some thought as to how you would adjust for such a condition.

Good luck...
Pips4life
  • #5
  • Sep 13, 2008 4:35pm Sep 13, 2008 4:35pm
Define the variable "int myTime" before init function, outside start() function. Then use the same code as in first post. I use this all the time and it must work (I hate calculating everything on every tick; I even restrict some calculations to once per day!).

chandra

PS: if you are going to use this inside a for or while loop, use the variable; instead of Time[0], you will have to use Time[i] for example.
  • #6
  • Sep 13, 2008 5:26pm Sep 13, 2008 5:26pm
Quoting achandrasekaran99
Define the variable "int myTime" before init function, outside start() function. Then use the same code as in first post. I use this all the time and it must work (I hate calculating everything on every tick; I even restrict some calculations to once per day!).

chandra

PS: if you are going to use this inside a for or while loop, use the variable; instead of Time[0], you will have to use Time[i] for example.

Hi chandra, dumbmoney,

My guess is dumbmoney already defined the variable outside the start() block but still experienced problems. He can, of course, confirm how he defined the variable.

My assumption was he did so and yet still experienced problems, so I offered some possible explanations.

There is one more reason that could apply, which is maybe the start() routine took an excessively long time and was interrupted before it completed?! Maybe you or someone else knows whether there is a maximum limit for an indicator after which MT4 abruptly cancels it. Is there? What is the limit? I vaguely recall something like 3.5 seconds but I have this question myself...

Pips4life
  • #7
  • Sep 13, 2008 5:47pm Sep 13, 2008 5:47pm
Not sure if this'll help, but it's the way I update indicators only once per bar...

Inserted Code
// Inits
datetime last_bar = 0;
int TimeFrame = 60;
At the top.

Inserted Code
   if (iTime(Symbol(), TimeFrame, 0) == last_bar) {
       // No new bars.
       return(0);
   }
   else {
       // Update the last bar clock.
       last_bar = iTime(Symbol(), TimeFrame, 0);
   }
During the start() call. Define TimeFrame as whatever timeframe you're working on. I used 60 minutes above, you can use whatever you need.
  • #8
  • Last Post: Edited Sep 15, 2008 6:06am Sep 14, 2008 9:11pm | Edited Sep 15, 2008 6:06am
Quoting pips4life
Hi chandra, dumbmoney,

My guess is dumbmoney already defined the variable outside the start() block but still experienced problems. He can, of course, confirm how he defined the variable.

My assumption was he did so and yet still experienced problems, so I offered some possible explanations.

There is one more reason that could apply, which is maybe the start() routine took an excessively long time and was interrupted before it completed?! Maybe you or someone else knows whether there is a maximum limit for an indicator after which MT4 abruptly cancels it. Is there? What is the limit? I vaguely recall something like 3.5 seconds but I have this question myself...

Pips4life
Hi Pips4life,

I had problems counting bars and so switched to monitoring the Time. It is not perfect, especially during startups. Occassionally I had to refresh the indies (very annoying when used in many charts). Now mostly I do not have the problem (very rare and I just restart MT4, instead of refreshing many indies in each chart). Recently I had problem often in 1M chart and I had to increase the Number of Bars in Chart (and History). That fixed the problem (now the counting Bars may also work well). I hope this gives something else to check out. EDIT: This helped only for Buffers related to plotting and may not help with other calculations.

I have never come across time limits, though I have come across line limits for MT4 indicator files (in some FerruFx multi indicators in forex-tsd).

chandra
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