Help with TS.computeRHSFunctionLinear

Hello,

I am trying to make a linear version of the heat.py example in the demos. I have added this to the code:

ts.setProblemType(0) 
ts.setType(ts.Type.RK)

ts.setRHSFunction(ts.computeRHSFunctionLinear, ode.gvec)

#ts.setIFunction(ode.evalFunction, ode.gvec)
#ts.setIJacobian(ode.evalJacobian, ode.mat)

And I get the follow error:

Traceback (most recent call last):
  File "heat_rk.py", line 129, in <module>
    ts.solve(x)
  File "TS.pyx", line 537, in petsc4py.PETSc.TS.solve (src/petsc4py.PETSc.c:137505)
  File "petscts.pxi", line 203, in petsc4py.PETSc.TS_RHSFunction (src/petsc4py.PETSc.c:28655)
  File "TS.pyx", line 167, in petsc4py.PETSc.TS.computeRHSFunctionLinear (src/petsc4py.PETSc.c:131167)
TypeError: computeRHSFunctionLinear() takes exactly 3 positional arguments (4 given)

I have also tried using a function like this (very similar to the original evalFunction):

    def evalFunction2(self, ts, t, x, f):
        self.g2l.scatter(x, self.lvec, PETSc.InsertMode.INSERT) # lvec is a work vector
        h = self.h
        with self.lvec as u:
            f.setArray(-2*u[1:-1]/h + u[:-2]/h + u[2:]/h) # Scale equation by volume element

ts.setRHSFunction(ode.evalFunction2, ode.gvec)

This runs, but it gives the following (several of the "Very small steps" line):

Very small steps: 0.000000
Very small steps: 0.000000
Very small steps: 0.000000
steps 100 (0 rejected, 0 SNES fails), nonlinear its 0, linear its 0
/home/kim/anaconda/lib/python2.7/site-packages/matplotlib/axes.py:4747: UserWarning: No labeled objects found. Use label='...' kwarg on individual plots.
  warnings.warn("No labeled objects found. "

I'm not really sure how this works, any help is appreciated.

Thanks, Kim

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