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C++ API

: [x, xdot, istate, msg] = daspk (fcn, x_0, xdot_0, t, t_crit)

Solve the set of differential-algebraic equations 

0 = f (x, xdot, t)

with 

x(t_0) = x_0, xdot(t_0) = xdot_0

The solution is returned in the matrices x and xdot, with each row in the result matrices corresponding to one of the elements in the vector t. The first element of t should be t_0 and correspond to the initial state of the system x_0 and its derivative xdot_0, so that the first row of the output x is x_0 and the first row of the output xdot is xdot_0.

The first argument, fcn, is a string, inline, or function handle that names the function f to call to compute the vector of residuals for the set of equations. It must have the form 

res = f (x, xdot, t)

in which x, xdot, and res are vectors, and t is a scalar.

If fcn is a two-element string array or a two-element cell array of strings, inline functions, or function handles, the first element names the function f described above, and the second element names a function to compute the modified Jacobian 

     df       df
jac = -- + c ------
     dx     d xdot

The modified Jacobian function must have the form 


jac = j (x, xdot, t, c)

The second and third arguments to daspk specify the initial condition of the states and their derivatives, and the fourth argument specifies a vector of output times at which the solution is desired, including the time corresponding to the initial condition.

The set of initial states and derivatives are not strictly required to be consistent. If they are not consistent, you must use the daspk_options function to provide additional information so that daspk can compute a consistent starting point.

The fifth argument is optional, and may be used to specify a set of times that the DAE solver should not integrate past. It is useful for avoiding difficulties with singularities and points where there is a discontinuity in the derivative.

After a successful computation, the value of istate will be greater than zero (consistent with the Fortran version of DASPK).

If the computation is not successful, the value of istate will be less than zero and msg will contain additional information.

You can use the function daspk_options to set optional parameters for daspk.

See also: dassl.

Package: octave