petsc-3.13.6 2020-09-29

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)

    PetscErrorCode 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.

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