I have pushed several changes to TS. Significant order dependence has been removed in the setup phase. The user visible changes are summarized below, please report any problems. TSSetIFunction() and TSSetRHSFunction() have an additional argument for the vector to compute the function value in. If PETSC_NULL is used, then one is created by the TS. TSSetMatrices() has been removed, use TSSetIFunction() and TSSetRHSFunction(), perhaps providing Jacobian matrices and TSComputeRHSFunctionLinear() and/or TSComputeRHSJacobianConstant(). See src/ts/examples/tutorials/ex{2,4,5,6}.c for examples. Changed TSStep() interface to only perform one step. Added TSSolve() to perform multiple steps with callbacks and monitors if desired. Added TSARKIMEX: additive Runge-Kutta implicit-explicit methods for multi-rate systems. Schemes of order 2 through 5 with L-stable implicit part and SSP explicit part are available.