Data part, timesteps

Timesteps are much the same as in the previous tutorial. We now take special action, however, in case the test_calculation is set to true. In that case simply a timestep of size $1$ is taken for imposing gravity and excavations. In this way a linear test calculation can be performed very fast, and you can check if linear results are plausible. The lines below show how this is done:

start_define
dtime 2.e-4
end_define
start_if test_calculation
control_timestep 700 1. 1.0
end_if
start_if_not test_calculation
control_timestep 700 dtime 1.0
end_if_not

The remaining part of the input file equals that of tutorial 3.