MQL4 Reference Math Functions MathSrand


Sets the starting point for generating a series of pseudorandom integers.

void  MathSrand(
   int  seed      // initializing number



[in]  Starting number for the sequence of random numbers.

Return Value

No return value.


The MathRand() function is used for generating a sequence of pseudorandom numbers. Call of MathSrand() with a certain initializing number allows to always produces the same sequence of pseudorandom numbers.

To ensure receipt of non-recurring sequence, use the call of MathSrand(GetTickCount()), since the value of GetTickCount() increases from the moment of the start of the operating system and is not repeated within 49 days, until the built-in counter of milliseconds overflows. Use of MathSrand(TimeCurrent()) is not suitable, because the TimeCurrent() function returns the time of the last tick, which can be unchanged for a long time, for example at the weekend.

Initialization of the random number generator using MathSrand() for indicators and Expert Advisors is better performed in the OnInit() handler; it saves you from the following multiple restarts of the generator in OnTick() and OnCalculate().

Instead of the MathSrand() function you can use the srand() function.


#property description "The indicator shows the central limit theorem, which states:"
#property description "The sum of a sufficiently large number of weakly dependent random variables, "
#property description "having approximately equal magnitude (none of the summands dominates,"
#property description "or makes a determining contribution to the sum), has a distribution close to normal."
#property indicator_separate_window
#property indicator_buffers 1
//--- Properties of the graphical construction
#property indicator_label1  "Label"
#property indicator_type1   DRAW_HISTOGRAM
#property indicator_color1  clrRoyalBlue
#property indicator_style1  STYLE_SOLID
#property indicator_width1  5
//--- An input variable
input int      sample_number=10;
//--- An indicator buffer to for drawing the distribution
double         LabelBuffer[];
//--- A counter of ticks
double         ticks_counter;
//| Custom indicator initialization function                         |
void OnInit()
//--- Binding an array and an indicator buffer
//--- turn the indicator buffer around from the present to the past
//--- Initialize the generator of random numbers
//--- Initialize the counter of ticks
//| Custom indicator iteration function                              |
int OnCalculate(const int rates_total,
                const int prev_calculated,
                const datetime &time[],
                const double &open[],
                const double &high[],
                const double &low[],
                const double &close[],
                const long &tick_volume[],
                const long &volume[],
                const int &spread[])
//--- For a zero counter reset the indicator buffer
   if(ticks_counter==0) ArrayInitialize(LabelBuffer,0);
//--- Increase the counter
//--- We should periodically reset the counter ticks, to revive the distribution
      Print("We've reset the indicator values, let's start filling the cells once again");
//--- Get a sample of random values as the sum of three numbers from 0 to 7
   for(int i=0;i<sample_number;i++)
      //--- Calculation of the index of the cell, where the random number falls as the sum of three other numbers
      int rand_index=0;
      //--- Get three random numbers from 0 to 7
      for(int k=0;k<3;k++)
         //--- A remainder in the division by 7 will return a value from 0 to 6
      //--- Increase the value in the cell number rand_index by 1
//--- Exit the OnCalculate() handler