how to fill Qlist in minimum time

hello every one, i am new to Qt,
I am trying to draw sound wave plot in sea water, for that i need a large no of points. So i used QList as i dont know how many points will be generated by the mathematical equation that i am using.
here is my code

Code:

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for(int j = 1 ; j < number_of_rays ; j++)
        {
            // int a = Incident_angles.at(j-1) + Angle_Difference;
            Incident_angles.insert(j, Incident_angles.at(j-1) + Angle_Difference);
            //qDebug() << "InCIDENT ANGLE = " << Incident_angles.at(j);
        }
 
        for (int j = 0; j < number_of_rays; j++)
        {
            SRP_X_Cordinate.clear();
            SRP_Y_Cordinate.clear();
 
            int factor = -1;
            counter = 0;
            SRP_X_Cordinate.insert(0,0);
            SRP_Y_Cordinate.insert(0,source_depth);
 
            Actual_Incident_Angle = Incident_angles.at(j);
            //qDebug() << "InCIDENT ANGLE = " << Incident_angles.at(j);
            if (Incident_angles.at(j) > 90)
            {
                factor = -factor;
                Actual_Incident_Angle = 180 - Incident_angles.at(j);
                //qDebug() << "Actual_Incident_Angle" << Actual_Incident_Angle;
            }
 
            if (SRP_Y_Cordinate.at(0) > 0)
            {
                if (Incident_angles.at(j)!= 90)
                {
                    Theta_1 = Actual_Incident_Angle*pi/180;
 
                    SRP_X_Cordinate.append(( SRP_X_Cordinate.at(counter) + difference_depth*tan(Theta_1)));
                    SRP_Y_Cordinate.append((SRP_Y_Cordinate.at(counter) + factor*difference_depth));
                    //qDebug() << "Inside not equal to 90";
                    double  C1 = Calculate_velocity(SRP_Y_Cordinate.at(counter));// + factor*0.001);
                    double  C2 = Calculate_velocity(SRP_Y_Cordinate.at(counter+1));// + factor*0.001);
 
                    double t = Temp_Time + (sqrt(pow((SRP_X_Cordinate.at(counter) - SRP_X_Cordinate.at(counter+1)),2) + pow((SRP_Y_Cordinate.at(counter) - SRP_Y_Cordinate.at(counter+1)),2)))/C1;
 
                    Ray_Time.insert(counter, t);
                    Temp_Time = Ray_Time.at(counter);
 
                    Theta_2 = Calculate_Angle(C1, C2, Theta_1);
 
                    counter = counter + 1;
 
                    while( SRP_X_Cordinate.at(counter) < max_range)
                    {
                        qDebug()<<"Theta_1 = "<< Theta_1;
                        qDebug()<<"Theta_2 = "<< Theta_2;
                        qDebug()<<"C1 = "<< C1;
                        qDebug()<<"C2 = "<< C2;
                        if(Theta_2 < (pi/2 - 0.001))
                        {
                            Theta_1 = Theta_2;
                            SRP_Y_Cordinate.append((SRP_Y_Cordinate.at(counter) + factor*difference_depth));
                            SRP_X_Cordinate.append((counter+1, SRP_X_Cordinate.at(counter) + difference_depth*tan(Theta_1)));
 
                            if( SRP_Y_Cordinate.at(counter+1) > 0.001 && SRP_Y_Cordinate.at(counter+1) < max_depth)
                            {
                                //qDebug()<<"SRP_X_Cordinate.at(counter) theta<90- - .01 = "<< SRP_Y_Cordinate.at(counter);
                                C1 = C2;
                                C2 = Calculate_velocity(SRP_Y_Cordinate.at(counter+1));// + factor*0.001);
                                Ray_Time.insert(counter, Temp_Time + (sqrt(pow((SRP_X_Cordinate.at(counter) - SRP_X_Cordinate.at(counter+1)),2) + pow((SRP_Y_Cordinate.at(counter) - SRP_Y_Cordinate.at(counter+1)),2)))/C1);
                                Temp_Time = Ray_Time.at(counter);
                                Theta_2 = Calculate_Angle(C1, C2, Theta_1);
                            }
 
                            else
                            {
                                //qDebug()<<"SRP_X_Cordinate.at(counter) theta<90- - .01 else cond = "<< SRP_Y_Cordinate.at(counter);
                                Theta_2 = Theta_1;
                                C2 = Calculate_velocity(SRP_Y_Cordinate.at(counter + 1));// + factor*0.001);
                                factor = - factor;
                                Ray_Time.insert(counter, Temp_Time + (sqrt(pow((SRP_X_Cordinate.at(counter) - SRP_X_Cordinate.at(counter+1)),2) + pow((SRP_Y_Cordinate.at(counter) - SRP_Y_Cordinate.at(counter+1)),2)))/C2);
                            }
                        }
                        else if(Theta_2 > (pi/2 + 0.0001))
                        {
                            qDebug()<<"SRP_X_Cordinate.at(counter) theta>90- - .01 = ";
                            factor = - factor;
                            Theta_1 = pi - Theta_2;
 
                            SRP_Y_Cordinate.append((SRP_Y_Cordinate.at(counter) + factor*difference_depth));
                            SRP_X_Cordinate.append((SRP_X_Cordinate.at(counter) + difference_depth*tan(Theta_1)));
 
                            C1 = C2;
                            C2 = Calculate_velocity(SRP_Y_Cordinate.at(counter+1));// + factor*0.001);
                            Ray_Time.insert(counter, Temp_Time + (sqrt(pow((SRP_X_Cordinate.at(counter) - SRP_X_Cordinate.at(counter+1)),2) + pow((SRP_Y_Cordinate.at(counter) - SRP_Y_Cordinate.at(counter+1)),2)))/C1);
                            Temp_Time = Ray_Time.at(counter);
 
                            Theta_2 = Calculate_Angle(C1, C2, Theta_1);
                        }
 
                        else
                        {
                            factor = - factor;
                            Theta_1 = 89*pi/180;
                            //qDebug()<<"SRP_X_Cordinate.at(counter) theta<90- - .01 = else condition  "<< SRP_Y_Cordinate.at(counter);
 
                            SRP_Y_Cordinate.append((SRP_Y_Cordinate.at(counter) + factor*difference_depth));
                            SRP_X_Cordinate.append((SRP_X_Cordinate.at(counter) + difference_depth*tan(Theta_1)));
 
                            C1 = C2;
                            C2 = Calculate_velocity(SRP_Y_Cordinate.at(counter+1));// + factor*0.001);
                            Ray_Time.insert(counter, Temp_Time + (sqrt(pow((SRP_X_Cordinate.at(counter) - SRP_X_Cordinate.at(counter+1)),2) + pow((SRP_Y_Cordinate.at(counter) - SRP_Y_Cordinate.at(counter+1)),2)))/C1);
                            Temp_Time = Ray_Time.at(counter);
 
                            Theta_2 = Calculate_Angle(C1, C2, Theta_1);
 
                        }
                        //  qDebug()<<"SRP_X_Cordinate.at(counter) theta<90- - .01 else cond = "<< SRP_Y_Cordinate.at(counter);
                        counter = counter + 1;
                    }
 
                    /* for( int r = 0; r< counter-1;r++)
                    {
                        Ray_Distance.insert(j, Ray_Distance.at(j) + sqrt(pow((SRP_X_Cordinate.at(r) - SRP_X_Cordinate.at(r+1)),2) + pow((SRP_Y_Cordinate.at(r) - SRP_Y_Cordinate.at(r+1)),2)));
                    }*/
                }
 
                else
                {
                    counter = 1;
                    SRP_X_Cordinate.insert(1,max_range);
                    SRP_Y_Cordinate.insert(1,source_depth);
                } 
            }
 
            SRP_2D_X_Cordinate.insert(j,SRP_X_Cordinate);
            SRP_2D_Y_Cordinate.insert(j,SRP_Y_Cordinate);
 
            //qDebug()<<" counter "<< counter;
            Data_points.insert(j,counter);
        }                                         ///////////////////  END FOR /////////////////////////////////

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this all i am doing on a button click and this is taking very long time

Please edit your post and put your code between [code] [/code] tags.
Then tell us what you expect us to do about it? There are a bunch of completely unknown functions, unknown numbers of loops, no idea what "a very long time", where you have measured the slow points to be, why you do this in a button click event is etc...

M really sorry that i didnt gave the post in proper format. And thanks that you paid a heed to my problem but i sorted ot the problem , actually i am calculating large no of X and Y coordinates and storing them in list and then retriving these point to draw line in paint event :). Its still complicated i have to disclose all my code thanks any way :)