Homogeneous Field and Derivative Values

In a typical run of reheating after chaotic inflation the rescaling constant $\phi_0$ will be set to the initial value of the inflaton in Planck units. We have generally found it most convenient to choose the starting point of our simulations at the moment when the program time derivative $f_{pr}'$ is equal to zero. Assuming no other fields have been excited, the inflaton will initially have value one and all other fields zero, and all field derivatives will initially be zero. However, the program allows you to set these initial values however you want. The values you give for these homogeneous modes should be in program variables, as determined by the rescaling parameter $A$. By default $A=1/\phi_0$ so if you set $\phi_0$ to the initial value of the inflaton and leave the default definition of $A$ you can set $\phi_{pr}=1$ initially and set any other nonzero initial field values in units of $\phi_0$.