c<html> c<head><title>newton1.f</title></head> c<body> c<pre> program newton c c Use a Newton iteration to solve the equation c c John Mahaffy 2/14/95 c c x**3+x-10=0 c c x - current approximation to the solution c f(x) - x**3+x-10 c dfdx - derivative of f with respect to x c xo - previous guess for solution c eps - convergence criterion c dx - change in solution approximation c it - number of iterations c itmax - maximum number of iterations c c implicitnone real x,f,dfdx,xo,eps,fx,dx,abs integer it,itmax c c c Now start executable fortran statements c
eps=1.e-5
itmax=10 print *,'What is your initial guess for the solution?' read *, x
xo= x*(1+10.*eps)
it=0 c <a name=1><font color=FF0000> dowhile (abs(x-xo).gt.eps*abs(x).and.it.le.itmax) c ^^^^^^^^^^^^^^^^^^^^^ </font></a>
it=it+1
xo=x
fx=f(xo,dfdx) c ^^^^^^^ c ^ This area between the parentheses is often refered to as the c ^ calling sequence, and contains arguments passed as input to c ^ the function and passed back as output from the function c
dx = -fx/dfdx
x=xo+dx print *, ' x = ',x,', f(x) = ',fx, ', dx = ',dx c<a name="ed"><font color="FF0000"> enddo c</a></font> stop end function f(x,deriv) c ^^^^^^^ c ^ These are the "dummy" arguments of the function. They need not be the c ^ same variable names as those appearing in the calling sequence c ^ where the function is referenced. However the number of arguments c ^ here should match the number in the reference to the function. c ^ It is also very important to match the data types between corresponding c ^ arguments here and in the calling sequence. c c Evaluate the function f(x)=x**3+x-10 c also return the derivative of the function c implicitnone real f,x,deriv c c John Mahaffy 2/14/95 c c Function arguments can receive data from the line of the program calling c the function, but can also pass data back to the program using the function. c Documentation of arguements should clearly delimit those receiving input for c the function from those transmitting output. c c INPUT c c x - independent variable c c OUTPUT c c f - value of the function c deriv - derivative of the function with respect to x c
deriv=3*x**2+1
f=x**3+x-10 return c<a name="end"><font color="FF0000"> end c</font></a> c</pre> c</body> c</html>
¤ Dauer der Verarbeitung: 0.23 Sekunden
(vorverarbeitet)
¤
Die Informationen auf dieser Webseite wurden
nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit,
noch Qualität der bereit gestellten Informationen zugesichert.
Bemerkung:
Die farbliche Syntaxdarstellung ist noch experimentell.
