c++ - newtons methods implementation -

-

i have posted few hours ago question newtons method,i got answers , want everybody,now have tried implement code itself

#include <iostream> #include <math.h> using namespace std; #define h powf(10,-7) #define pi 180 float funct(float x){      return cos(x)-x;   } float derivative (float x){     return (( funct(x+h)-funct(x-h))/(2*h));  } int main(){     float tol=.001;     int n=3;     float p0=pi/4;     float p=0;     int i=1;     while(i<n){          p=p0-(float)funct(p0)/derivative(p0);         if ((p-p0)<tol){             cout<<p<<endl;             break;          }           i=i+1;         p0=p;       if (i>=n){         cout<<"solution not found "<<endl;         break;     }     }        return 0; }

but writes output "solution not found",in book after 3 iteration when n=3 ,it finds solution .7390851332,so question how small should change h or how should change code such that,get correct answer?

several things:

  1. 2 iterations going enough in best case.
  2. you need make sure starting point convergent.
  3. be aware of destructive cancellation in derivative function. subtracting 2 numbers close each other difference lose lot of precision.

to expand on last point, general method decrease h value converges. mentioned in previous question, "adjusting" h method (algebraically) reduces secant method.


Comments

Post a Comment

Popular posts from this blog

objective c - Change font of selected text in UITextView -

-
can suggest me how change font of selected text in uitextview.i cannot use uiwebview since have edit text. have seen pages app.how possible in app. see formatting text within uilabel differently . since need editing, should @ javascript-based editors such ckeditor or tinymce . highly recommend wwdc 2011 video session 511: "rich text editing in safari on ios."
Read more

php - Accessing POST data in Facebook cavas app -

-
so i've got simple form in canvas / iframe facebook app, , i'm trying pass along values post. reading on s.o. , fb's latest docs, understand it, data send via post form can accessed on receiving end $_request object. i read on thread on s.o. in order post forms work need pass along input named "signed_request" value current signed_request (i have signed request working ok otherwise...all login , authentication stuff working fine). isnt mentioned anywhere in official fb docs. so problem comes in $_request object signed request, , bunch of other session stuff. form inputs found. the way can read them set method of form "request" isn't real form method. takes of inputs , sends them args in url. horrible. here's sample page canvas app form i'm using try debug (leaving out authentication stuff): <form enctype="application/x-www-form-urlencoded" method="post" target="_top" id="my_form" action=...
Read more

c# - Getting control value when switching a view as part of a multiview -

-
i have following code in aspx page: <asp:button id="display_button" runat="server" text="display" onclick="button1_click" /> &nbsp; <asp:button id="edit_button" runat="server" text="edit" onclick="button2_click" /> &nbsp; <asp:button id="save_button" runat="server" text="save" onclick="button3_click" visible="false" /> &nbsp; <asp:multiview id="multiview1" runat="server" activeviewindex="0"> <asp:view id="view1" runat="server"> <asp:formview id="view_program" runat="server"> <itemtemplate> <%# eval("status").tostring().trim() %> </itemtemplate> </asp:formview> </asp:view> <asp:view id="view2" runat="server"> ...
Read more