# Re: what is wrong with this code?can someone walk me through this?

*From*: "deltaseq0" <deltaseq0@xxxxxxxxxx>*Date*: Fri, 28 Mar 2008 16:24:28 -0400

"e p chandler" <epc8@xxxxxxxx> wrote in message

news:a77a612e-3d24-4f29-bd25-1c328ca01d1b@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

On Mar 26, 10:08 pm, madhu0...@xxxxxxxxx wrote:

i did not use any diagnostic program. i dont even know anything abt

it. i dont know anything abt fortran or coding..this is my project at

school thats due in 20days..cani run this code on any compiler, i mean

is it compatible with any? shud it return the same values on any

compiler?

pls bear with my silly questions, i am very stressed out abt this..

You CAN get your program to compile if you

1. remove leading spaces on each line

2. change

EXTERNAL FX, FY, DERIV_FX, DERIV_FY

to

EXTERNAL FX, FY

3. compile as free format source

DERIV_FX and DERIV_FY are variables NOT functions passed as arguments

to routines so there is no need to make them EXTERNAL.

Making the numerical changes suggested by others DOES not make any

difference in the output except for trailing digits for the value of

Stokes.

When I compiled and ran the program it printed:

*** Parameters read from file particle.par

***

The Stokes is equal to:

0.0006589939662307433

n_t= 1. y= 0.000023255106965997813

n_t= 0.995 y= 0.000023138831431167825

n_t= 0.990025 y= 0.000023023137274011985

n_t= 0.985074875 y= 0.000022908021587641927

n_t= 0.9801495006250001 y= 0.000022793481479703716

n_t= 0.9752487531218751 y= 0.0000226795140723052

n_t= 0.9703725093562657 y= 0.000022566116501943672

n_t= 0.9655206468094844 y= 0.000022453285919433955

n_t= 0.960693043575437 y= 0.000022341019489836785

Note that your value of Stokes is NOT between 0.1 and 2.0 as desired.

Maybe better input data will help. Maybe better values for other

constants will help.

Check the program listing against your formulas and equations. Verify

that your program is correctly transcribed.

Insert WRITE statements in the program to display the value of

variables as the program runs. Compare these to manual calculations.

What are reasonable ranges for the input variables? Try combinations

of LOW, MID and HIGH values for the input variables and see what you

get.

At this point there is no substitute for pouring over your program

listing and output with paper, pencil and a calculator.

With MINOR changes the program DOES compile. You don't have obvious

errors involving mismatched arguments to subroutines or common blocks

that do not match. You may have other

programming errors

logical errors

bad numerical behavior.

Other than the "Non-Fortran" flavor of your program, there is nothing

obviously wrong that jumps out except

goto 5

followed by

STOP. :-).

Good luck.

-- e

So, from the various suggestions given by others in this post, you should be

able to compile and run your program. You can then get answers but don't

know if they are correct or where the problem may be if there is one.

Your problem description seems well defined with parameters and differential

equations. These equations seem to require numerical solutions. It may be

more efficient to take one step back from FORTRAN and program the problem in

a computer algebra system such as MathCAD, Matlab, etc.

This approach has several advantages. You can be better assured that the

numerical results will reflect only your input and not a coding error If the

results look strange, you can more easily focus your attention. You can play

around with the problem statement changing input and checking output. You

will be free of possible errors in your differentiation and integration

procedures. You will also be able to output intermediate results which you

can then compare to your FORTRAN code. Finally, some CAS programs have

graphical tools that are simple to implement and can be very valuable, for

example showing where functions become discontinuous. In the end, you will

have a program that you know works (or not) and can then (re)program in

FORTRAN. These CAS programs are easy to use but are expensive. Universities

probably can provide free access.

.

**References**:**what is wrong with this code?can someone walk me through this?***From:*madhu0319

**Re: what is wrong with this code?can someone walk me through this?***From:*e p chandler

**Re: what is wrong with this code?can someone walk me through this?***From:*madhu0319

**Re: what is wrong with this code?can someone walk me through this?***From:*e p chandler

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