Need in solving a programm in FOTRAN

[Sampath Emani]

Friends,
i have written a program in FOTRAN for solving a equation [f(x0,y0)= 2*(y**2)+5]
I'm in the learning stage of FOTRAN. So please don't mind if my program has got any silly mistakes.
Please help in executing the program.

program rungekutta


print *,' DIFFERENTIAL EQUATION WITH 1 VARIABLE OF ORDER 1'

print*,"enter the value of x0"
read*,x

print*,"enter the value of y0"
read*,y

print*,"enter the value of step size"
read*,h

print*,"solution for the equation is",rk(x0,y0,h)


call runge(m,f1,n,h,x1)

end

function rk(y) result(r)

!Example: y'=(2*y^2+5)

real y,r

r = (2*(y**2)+5)
end function rk(y)

Subroutine runge(m,f1,n,h,x1)

integer f1,i,j,m,n,h

real x,w1,w2,w3,w4,x0,y;

do i=1, m
ni = (i - 1) * f1 - 1
do j=1, f1
x = x1 + h * (n + j)
w1 = h * f(x0,y0)
w2 = h * f(x0+h/2, y0+w1/2)
w3 = h * f(x0+h/2, y0+w2/2)
w4 = h * f(x0+h, y0+w3)
x = x0 + h

x = y + (w1 + w2 + w2 + w3 + w3 + w4) / 6

end do

end do

end

 

[gsal]

what does the subroutine runge do for you? it is not being used anywhere.

why if function rk is declared with 1 argument, you pass 3 to it?

 

[Sampath Emani]

yes sir,
i do agree. but I'm not able not correct that .
Can u help me in writing the correct step.
I took an equation (2*(y**2)+5)
i want to solve this using Runge kutta.
Thanks in advance

 

[Louisa]

Friends,
i have written a program in FOTRAN for solving a equation [f(x0,y0)= 2*(y**2)+5]
I'm in the learning stage of FOTRAN. So please don't mind if my program has got any silly mistakes.
Please help in executing the program.

program rungekutta


print *,' DIFFERENTIAL EQUATION WITH 1 VARIABLE OF ORDER 1'

print*,"enter the value of x0"
read*,x

print*,"enter the value of y0"
read*,y

print*,"enter the value of step size"
read*,h

print*,"solution for the equation is",rk(x0,y0,h)


call runge(m,f1,n,h,x1)

end

function rk(y) result(r)

!Example: y'=(2*y^2+5)

real y,r

r = (2*(y**2)+5)
end function rk(y)

Subroutine runge(m,f1,n,h,x1)

integer f1,i,j,m,n,h

real x,w1,w2,w3,w4,x0,y;

do i=1, m
ni = (i - 1) * f1 - 1
do j=1, f1
x = x1 + h * (n + j)
w1 = h * f(x0,y0)
w2 = h * f(x0+h/2, y0+w1/2)
w3 = h * f(x0+h/2, y0+w2/2)
w4 = h * f(x0+h, y0+w3)
x = x0 + h

x = y + (w1 + w2 + w2 + w3 + w3 + w4) / 6

end do

end do

end

There are at least several problems that you need to rectify.
(In future, include all the error messages with your post, along with the
source.)

1. You need "IMPLICIT NONE" in the program and in each subroutine
and function.

2. What is "f"?

3. when you invoke rk, it is with 3 arguments.
Yet the function is defined with only one dummy argument.

4. You requested the input of "x0", but you read the value into "x", etc.

 

[LudusRex]

subroutine runge

I would first commend the individual for taking the initiative to learn and write a program in FORTRAN. It is important to note that making mistakes is a natural part of the learning process and it is through these mistakes that we can improve and refine our skills.

In order to help execute the program, I would suggest the following steps:

1. Review the code and check for any syntax errors or typos. This can be done by running the program through a compiler or using an online FORTRAN editor.

2. If there are no syntax errors, try running the program with different input values to see if it produces the expected output.

3. If the program still does not work, it would be helpful to provide more information such as the specific error message or any issues encountered during execution.

Additionally, I would recommend utilizing online resources or seeking assistance from a more experienced FORTRAN programmer to help identify any potential errors and provide guidance on how to improve the program.

In summary, learning a new programming language can be challenging, but with practice and perseverance, it is possible to overcome any mistakes and improve one's skills. I wish the individual the best of luck in their FORTRAN journey.