petsc-3.11.4 2019-09-28

TSSetIFunction

Set the function to compute F(t,U,U_t) where F() = 0 is the DAE to be solved.

#include "petscts.h"  
PetscErrorCode  TSSetIFunction(TS ts,Vec r,TSIFunction f,void *ctx)

Logically Collective on TS

	ts	- the TS context obtained from TSCreate()
	r	- vector to hold the residual (or NULL to have it created internally)
	f	- the function evaluation routine
	ctx	- user-defined context for private data for the function evaluation routine (may be NULL)

 f(TS ts,PetscReal t,Vec u,Vec u_t,Vec F,ctx);

	t	- time at step/stage being solved
	u	- state vector
	u_t	- time derivative of state vector
	F	- function vector
	ctx	- [optional] user-defined context for matrix evaluation routine

The user MUST call either this routine or TSSetRHSFunction() to define the ODE. When solving DAEs you must use this function.

TS, timestep, set, DAE, Jacobian

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