How to deal with imprecision in Google's latest version of the Super Tuesday Update - General

Fernando Carreiro 2022.01.30 12:57 #11

Jian Chen #: I'm not sure but I did a simple test. The NormalizeDouble function should be working. Output: 2022.01.30 20:30:28.360 MyTest1 (EURUSD,H1) Normalize double test: 0.2999999 = 0.30

You are using DoubleToString to the same number of digits, which cancels out any possible "bug" that NormalizeDouble may or may not have. Your test does not serve as a satisfactory evaluation of the situation.

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Alexandre Borela 2022.01.30 13:06 #12

Dark Ryd3r #:
I confirm NormalizeDouble does not work and its an official bug and must be reported to ServiceDesk

It's not an issue with the NormalizeDouble, it's just an UI issue. The current UI is showing what doubles actually are,
they have always been imprecise, it's just that before the update, the UI would not show the actual value.

All programmers should know how to deal with double/float imprecision, but when it comes to user experience, the
previous behavior of the UI was ideal.

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Fernando Carreiro 2022.01.30 13:13 #13

Here are my results with the following script:

double dbValue = 0.2999999; Print( "MT5 Build: ", __MQLBUILD__, ", Value: ", dbValue, ", Normalised: ", NormalizeDouble( dbValue, 2 ) );

2022.01.30 13:07:54.747 TestNormalize (EURUSD,H1)       MT5 Build: 3180, Value: 0.29999989999999999, Normalised: 0.29999999999999999
2022.01.30 13:19:06.532 TestNormalize (EURUSD,H1)       MT5 Build: 3164, Value: 0.2999999, Normalised: 0.3
2022.01.30 13:10:45.504 TestNormalize (EURUSD,H1)       MT5 Build: 3000, Value: 0.2999999, Normalised: 0.3

So it seems, that functionality in both the display and the NormalizeDouble has changed in some way in this new build.

EDIT: See later posts!

Alexandre Borela 2022.01.30 13:17 #14

Fernando Carreiro #:

Here are my results with the following script:

So it seems, that NormalizeDouble is in fact flawed in some way in this new build.

The only flaw is the fact that the function still exists, instead of pointing people to articles teaching about floating point,
it promises something impossible with them that is to round it to specific numbers. Some numbers just can't be represented.

https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

https://floating-point-gui.de/

In both your examples, the double's value is actually ~0.299999999... the print function is what rounded the value.

Metaquotes should deprecate it, as this function causes confusion to beginners everyday.

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Fernando Carreiro 2022.01.30 13:23 #15

Alexandre Borela #: The only flaw is the fact that the function still exists, instead of pointing people to articles teaching about floating point, it promises something impossible with them that is to round it to specific numbers. Some numbers just can't be represented.

Yes, I am well aware of the downfall of using the function, and I have on many threads advocated NEVER using it. I am merely posting my results in order to help second those users that wish to request MetaQuotes to restore the previous functionality of the function and the display of parameters in the properties panel.

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Fernando Carreiro 2022.01.30 13:49 #16

Here is a more thorough test with the following script:

double dbValue = 0.2999999, dbNormalised = NormalizeDouble( dbValue, 2 );
Print( "MT Build: ", __MQLBUILD__, ", Value: ",                 dbValue,       ", Normalised: ", dbNormalised                       );
Print( "MT Build: ", __MQLBUILD__, ", Value: ", DoubleToString( dbValue     ), ", Normalised: ", DoubleToString( dbNormalised     ) );
Print( "MT Build: ", __MQLBUILD__, ", Value: ", DoubleToString( dbValue, 8  ), ", Normalised: ", DoubleToString( dbNormalised, 8  ) );
Print( "MT Build: ", __MQLBUILD__, ", Value: ", DoubleToString( dbValue, 16 ), ", Normalised: ", DoubleToString( dbNormalised, 16 ) );

2022.01.30 13:46:29.283 TestNormalize (EURUSD,H1)       MT Build: 3180, Value: 0.29999989999999999, Normalised: 0.29999999999999999
2022.01.30 13:46:29.283 TestNormalize (EURUSD,H1)       MT Build: 3180, Value: 0.29999990, Normalised: 0.30000000
2022.01.30 13:46:29.283 TestNormalize (EURUSD,H1)       MT Build: 3180, Value: 0.29999990, Normalised: 0.30000000
2022.01.30 13:46:29.283 TestNormalize (EURUSD,H1)       MT Build: 3180, Value: 0.2999999000000000, Normalised: 0.3000000000000000

2022.01.30 13:47:28.279 TestNormalize (EURUSD,H1)       MT Build: 3164, Value: 0.2999999, Normalised: 0.3
2022.01.30 13:47:28.280 TestNormalize (EURUSD,H1)       MT Build: 3164, Value: 0.29999990, Normalised: 0.30000000
2022.01.30 13:47:28.280 TestNormalize (EURUSD,H1)       MT Build: 3164, Value: 0.29999990, Normalised: 0.30000000
2022.01.30 13:47:28.280 TestNormalize (EURUSD,H1)       MT Build: 3164, Value: 0.2999999000000000, Normalised: 0.3000000000000000

From the above, it seems that it is more of only a default display problem and that NormalizeDouble is still working as before.

Fernando Carreiro 2022.01.30 14:01 #17

One more test to see if the normalising function has changed or not with the following script:

union LongDouble 
{ 
  long   long_value; 
  double double_value; 
};

void OnStart()
{
   double dbValue = 0.2999999, dbNormalised = NormalizeDouble( dbValue, 2 );
   LongDouble ldNormalised;
   ldNormalised.double_value = dbNormalised; 
   Print( "MT Build: ", __MQLBUILD__, ", Normalised Value as a Long: ", ldNormalised.long_value );
};

2022.01.30 13:56:53.638 TestNormalize (EURUSD,H1)       MT Build: 3164, Normalised Value as a Long: 4599075939470750515
2022.01.30 13:57:59.295 TestNormalize (EURUSD,H1)       MT Build: 3180, Normalised Value as a Long: 4599075939470750515

It seems to be working as before. The only difference seems to be the default display of the numbers and not the underlying data.

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Dark Ryd3r 2022.01.30 14:18 #18

Jian Chen #:

I'm not sure but I did a simple test. The NormalizeDouble function should be working.

Output:

2022.01.30 20:30:28.360 MyTest1 (EURUSD,H1) Normalize double test: 0.2999999 = 0.30

try this

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
void  OnStart () {
//---
   Print ( "Normalize double test: 0.2999999 = ",  NormalizeDouble ( 0.299999,  2 ));

} 
//+------------------------------------------------------------------+

Dark Ryd3r 2022.01.30 14:20 #19

Alexandre Borela #:
It's not an issue with the NormalizeDouble, it's just an UI issue. The current UI is showing what doubles actually are,
they have always been imprecise, it's just that before the update, the UI would not show the actual value.

All programmers should know how to deal with double/float imprecision, but when it comes to user experience, the
previous behavior of the UI was ideal.

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
void  OnStart () {
//---
   Print ( "Normalize double test: 0.2999999 = ",  NormalizeDouble ( 0.299999,  2 ));

} 
//+------------------------------------------------------------------+

My EA Stopped sending orders due to this bug, so i explored and found this. Its an issue with NormalizeDouble which output can be seen

Fernando Carreiro 2022.01.30 14:23 #20

Dark Ryd3r #: My EA Stopped sending orders due to this bug, so i explored and found this. Its an issue with NormalizeDouble which output can be seen

No, NormalizeDouble seems to be working just as before with no change. It seems to be only a "display" problem. See my previous posts here on the thread, especially Post #17.

MT5 update [build 3180] decimal input variable bug - page 2