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See the recommended documentation of this function
dassl
differential algebraic equation
Calling Sequence
[r [,hd]]=dassl(x0,t0,t [,atol,[rtol]],res [,jac] [,info] [,hd])
Arguments
- x0
is either
y0
(ydot0
is estimated bydassl
with zero as first estimate) or the matrix[y0 ydot0]
.g(t,y0,ydot0)
must be equal to zero. If you only know an estimate ofydot0
setinfo(7)=1
- y0
real column vector of initial conditions.
- ydot0
real column vector of the time derivative of
y
att0
(may be an estimate).
- t0
real number is the initial instant.
- t
real scalar or vector. Gives instants for which you want the solution. Note that you can get solution at each dassl's step point by setting
info(2)=1
.- atol,rtol
real scalars or column vectors of same size as
y
.atol,rtol
give respectively absolute and relative error tolerances of solution. If vectors the tolerances are specified for each component ofy
.- res
external (function or list or string). Computes the value of
g(t,y,ydot)
. It may be :A Scilab function.
Its calling sequence must be
[r,ires]=res(t,y,ydot)
andres
must return the residuer=g(t,y,ydot)
and error flagires
.ires = 0
ifres
succeeds to computer
,=-1
if residue is locally not defined for(t,y,ydot)
,=-2
if parameters are out of admissible range.A list.
This form allows to pass parameters other than t,y,ydot to the function. It must be as follows:
list(res,x1,x2,...)
where the calling sequence of the function
res
is nowr=res(t,y,ydot,x1,x2,...)
res
still returnsr=g(t,y,ydot)
as a function of(t,y,ydot,x1,x2,...)
.A string.
it must refer to the name of a C or fortran subroutine linked with Scilab.
In C The calling sequence must be:
In Fortran it must be:
subroutine res(t,y,yd,r,ires,rpar,ipar) double precision t, y(*),yd(*),r(*),rpar(*) integer ires,ipar(*)
The rpar and ipar arrays must be present but cannot be used.
- jac
external (function or list or string). Computes the value of
dg/dy+cj*dg/dydot
for a given value of parametercj
A Scilab function.
Its calling sequence must be
r=jac(t,y,ydot,cj)
and thejac
function must returnr=dg(t,y,ydot)/dy+cj*dg(t,y,ydot)/dydot
wherecj
is a real scalarA list.
it must be as follows
list(jac,x1,x2,...)
where the calling sequence of the function
jac
is nowr=jac(t,y,ydot,cj,x1,x2,...)
jac
still returnsdg/dy+cj*dg/dydot
as a function of(t,y,ydot,cj,x1,x2,...)
.A character string.
it must refer to the name of a fortran subroutine linked with scilab
In C The calling sequence must be:
In Fortran it must be:
subroutine jac(t,y,yd,pd,cj,rpar,ipar) double precision t, y(*),yd(*),pd(*),cj,rpar(*) integer ipar(*)
- info
optional list which contains
7
elements. Default value is list([],0,[],[],[],0,0);- info(1)
real scalar which gives the maximum time for which
g
is allowed to be evaluated or an empty matrix[]
if no limits imposed for time.- info(2)
flag which indicates if
dassl
returns its intermediate computed values (flag=1
) or only the user specified time point values (flag=0
).- info(3)
2
components vector which give the definition[ml,mu]
of band matrix computed byjac
;r(i - j + ml + mu + 1,j) = "dg(i)/dy(j)+cj*dg(i)/dydot(j)"
. Ifjac
returns a full matrix setinfo(3)=[]
.- info(4)
real scalar which gives the maximum step size. Set
info(4)=[]
if no limitation.- info(5)
real scalar which gives the initial step size. Set
info(4)=[]
if not specified.- info(6)
set
info(6)=1
if the solution is known to be non negative, else set .- info(7)
set
info(7)=1
ifydot0
is just an estimation,info(7)=0
ifg(t0,y0,ydot0)=0
.
- hd
real vector which allows to store the
dassl
context and to resume integration- r
real matrix . Each column is the vector [t;x(t);xdot(t)] where t is time index for which the solution had been computed
Description
The dassl function integrate the algebro-differencial equation and
returns the evolution ofy
a given time points
g(t,y,ydot)=0 y(t0)=y0 and ydot(t0)=ydot0
Examples
function [r, ires]=chemres(t, y, yd) r=[-0.04*y(1)+1d4*y(2)*y(3)-yd(1) 0.04*y(1)-1d4*y(2)*y(3)-3d7*y(2)*y(2)-yd(2) y(1)+y(2)+y(3)-1]; ires=0 endfunction function pd=chemjac(x, y, yd, cj) pd=[-0.04-cj , 1d4*y(3) , 1d4*y(2); 0.04 ,-1d4*y(3)-2*3d7*y(2)-cj ,-1d4*y(2); 1 , 1 , 1 ] endfunction y0=[1;0;0]; yd0=[-0.04;0.04;0]; t=[1.d-5:0.02:.4,0.41:.1:4,40,400,4000,40000,4d5,4d6,4d7,4d8,4d9,4d10]; y=dassl([y0,yd0],0,t,chemres); info=list([],0,[],[],[],0,0); info(2)=1; y=dassl([y0,yd0],0,4d10,chemres,info); y=dassl([y0,yd0],0,4d10,chemres,chemjac,info); //Using extra argument for parameters //----------------------------------- function [r, ires]=chemres(t, y, yd, a, b, c) r=[-a*y(1)+b*y(2)*y(3)-yd(1) a*y(1)-b*y(2)*y(3)-c*y(2)*y(2)-yd(2) y(1)+y(2)+y(3)-1]; ires=0 endfunction function pd=chemjac(x, y, yd, cj, a, b, c) pd=[-a-cj , b*y(3) , b*y(2); a ,-b*y(3)-2*c*y(2)-cj ,-b*y(2); 1 , 1 , 1 ] endfunction y=dassl([y0,yd0],0,t,list(chemres,0.04,1d4,3d7),list(chemjac,0.04,1d4,3d7)); //using C code //------------ // - create the C code rescode=['void chemres(double *t, double y[], double yd[], double r[], int *ires, double rpar[], int ipar[])' ' {' ' r[0] = -0.04*y[0]+1.0e4*y[1]*y[2] -yd[0];' ' r[1] = 0.04*y[0]-1.0e4*y[1]*y[2]-3.0e7*y[1]*y[1]-yd[1];' ' r[2] = y[0]+y[1]+y[2]-1;' ' *ires = 0;' ' }']; jaccode=['void chemjac(double *t, double y[], double yd[], double pd[], double *cj, double rpar[], int ipar[])' ' {' ' /* first column*/' ' pd[0] = -0.04-*cj;' ' pd[1] = 0.04;' ' pd[2] = 1.0;' ' /* second column*/' ' pd[3] = 1.0e4*y[2];' ' pd[4] = -1.0e4*y[2]-2*3.0e7*y[1]-*cj;' ' pd[5] = 1.0;' ' /* third column*/' ' pd[6] = 1.0e4*y[1];' ' pd[7] = -1.0e4*y[1];' ' pd[8] = 1.0;' ' }']; mputl([rescode;jaccode],TMPDIR+'/mycode.c') //create the C file // - compile it ilib_for_link(['chemres','chemjac'],'mycode.c',[],'c',TMPDIR+'/Makefile',TMPDIR+'/loader.sce');//compile // - link it with Scilab exec(TMPDIR+'/loader.sce') //incremental linking // - call dassl y=dassl([y0,yd0],0,t,'chemres','chemjac');
See Also
<< dasrt | Differential Equations, Integration | feval >> |