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Help need for Differential algebraic equations
From: |
genehacker |
Subject: |
Help need for Differential algebraic equations |
Date: |
Wed, 8 Oct 2008 15:22:11 -0700 (PDT) |
Hi all,
I am new to octave and i love it the best as an open source alternative
to matlab. I used lsode to solve ordinary diff equations, but now I do also
have some algebraic equations to solve along.
I came across this function 'dassl', which is supposed to solve differential
algebraic equations, but have problems using it. This is how i use it
currently and below is the error message. I have no idea what it is. Please
help!
******code*****
function xdot = f(x,xdot,t);
%define all parameter values viz. k12, k23,f86 etc here
xdot = zeros(9,1);
xdot(2) = k12*x(1) - k23*x(2);
xdot(3) = k23*x(2);
xdot(5) = k45*x(4) - k56*x(5);
xdot(6) = k56*x(5) - k67*x(6);
xdot(7) = k67*x(6);
x(8) = f86*x(6);
x(9) = f29*x(2);
endfunction;
x0 = ones(9,1)';
xdot0 =zeros(9,1)';
t = linspace(0,50,50);
dassl("f",x0,xdot0,t)
*****output******
***MESSAGE FROM ROUTINE DDASSL IN LIBRARY SLATEC.
***POTENTIALLY RECOVERABLE ERROR, PROG ABORTED, TRACEBACK REQUESTED
* AT T = 0.000000E+00 AND STEPSIZE H = 1.594388E-05 THE ITERATION
* MATRIX IS SINGULAR
* ERROR NUMBER = -8
*
***END OF MESSAGE
***JOB ABORT DUE TO UNRECOVERED ERROR.
0 ERROR MESSAGE SUMMARY
LIBRARY SUBROUTINE MESSAGE START NERR LEVEL COUNT
SLATEC DDASSL AT T = 0.000000E+ -8 1 1
error: exception encountered in Fortran subroutine ddassl_
error: caught execution error in library function
--
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- Help need for Differential algebraic equations,
genehacker <=