Normalize Price?

[Demosfen]

Hey guys, can someone explain me the idea behind this code?

double NormalizePrice(double p)
{
    double ts=SymbolInfoDouble(_Symbol, SYMBOL_TRADE_TICK_SIZE);
    return(MathRound(p/ts)*ts);
}

Can it not be simply replaced with this?

NormalizeDouble(value, Digits())

Help very much appreciated!

[Seng Joo Thio]

Demosfen:

Hey guys, can someone explain me the idea behind this code?

Can it not be simply replaced with this?

Help very much appreciated!

When the least significant digit of SYMBOL_TRADE_TICK_SIZE is a '1' (as in currencies market), NormalizeDouble(value, Digits()) will work so long as Digits() represent the right number of floating points.

So the function you showed is more like a "catch all" solution - so that the same code works for other markets.

[William Roeder]

NormalizeDouble, It's use is usually wrong,

1. Floating point has infinite number of decimals, it's your not understanding floating point and that some numbers can't be represented exactly. (like 1/10.)
             Double-precision floating-point format - Wikipedia, the free encyclopedia

   See also The == operand. - MQL4 programming forum

2. Print out your values to the precision you want with DoubleToString - Conversion Functions - MQL4 Reference.

3. SL/TP (stops) need to be normalized to tick size (not Point.) (On 5Digit Broker Stops are only allowed to be placed on full pip values. How to find out in mql? - MQL4 programming forum) and abide by the limits Requirements and Limitations in Making Trades - Appendixes - MQL4 Tutorial and that requires understanding floating point equality Can price != price ? - MQL4 programming forum
4. Open price for pending orders need to be adjusted. On Currencies, Point == TickSize, so you will get the same answer, but it won't work on Metals. So do it right: Trailing Bar Entry EA - MQL4 programming forum or Bid/Ask: (No Need) to use NormalizeDouble in OrderSend - MQL4 programming forum
5. Lot size must also be adjusted to a multiple of LotStep and check against min and max. If that is not a power of 1/10 then NormalizeDouble is wrong. Do it right.
6. MathRound() and NormalizeDouble() are rounding in a different way. Make it explicit.
             MT4:NormalizeDouble - General - MQL5 programming forum
             How to Normalize - Expert Advisors and Automated Trading - MQL5 programming forum

[amrali]

William Roeder:
NormalizeDouble, It's use is usually wrong,

1. Floating point has infinite number of decimals, it's your not understanding floating point and that some numbers can't be represented exactly. (like 1/10.)
             Double-precision floating-point format - Wikipedia, the free encyclopedia

   See also The == operand. - MQL4 programming forum

2. Print out your values to the precision you want with DoubleToString - Conversion Functions - MQL4 Reference.

3. SL/TP (stops) need to be normalized to tick size (not Point.) (On 5Digit Broker Stops are only allowed to be placed on full pip values. How to find out in mql? - MQL4 programming forum) and abide by the limits Requirements and Limitations in Making Trades - Appendixes - MQL4 Tutorial and that requires understanding floating point equality Can price != price ? - MQL4 programming forum
4. Open price for pending orders need to be adjusted. On Currencies, Point == TickSize, so you will get the same answer, but it won't work on Metals. So do it right: Trailing Bar Entry EA - MQL4 programming forum or Bid/Ask: (No Need) to use NormalizeDouble in OrderSend - MQL4 programming forum
5. Lot size must also be adjusted to a multiple of LotStep and check against min and max. If that is not a power of 1/10 then NormalizeDouble is wrong. Do it right.
6. MathRound() and NormalizeDouble() are rounding in a different way. Make it explicit.
             MT4:NormalizeDouble - General - MQL5 programming forum
             How to Normalize - Expert Advisors and Automated Trading - MQL5 programming forum

Never ever trust that

[amrali]

double NormalizePrice(double p)
{
    double ts=SymbolInfoDouble(_Symbol, SYMBOL_TRADE_TICK_SIZE);
    return(NormalizDouble(p/ts,0)*ts);
}

NormalizeDouble() is optimized to handle rounding of edge numbers better than MathRound() 

[amrali]

Normalization (rounding) is needed only after you do any math operation (+ - * /), as this introduces minor errors in the result. That includes calculating a takeprofit/stoploss/pending order price/lotsize, etc..

If no math operator is involved, then rounding is not needed. 

For example:

double bid=SymbolInfoDouble(_Symbol, SYMBOL_BID);

There is no need to normalize here. 

[Demosfen]

Thank you all for your comments!