

![0_image_0.png](0_image_0.png) 
this solution. Although the two solutions differ in terms of step contents, we notice that they have the same step length. The difference in step contents can be explained by the fact that the de-ordering algorithm relaxes the ordering relations in the plan, allowing for some actions to come earlier, while Pushup **always moves actions towards the end of the plan.**
We have run more comprehensive studies in three different domains (Logistics, Satellite and Zenotravel), and found that in no case is the step length of a plan produced by AltAltp improved by the post-processing routine (we omit the comparison plots since they essentially show the curves corresponding to AltAltp and AltAltp with post-processing **coincident**).12

## 4.3 Ablation Studies

This section attempts to analyze the impact of the different parts of AltAltp **on its performance.**
Utility of the Pushup Procedure: **Figure 18 shows the effects of running** AltAltp **with**
and without the Pushup **procedure (but with the fattening procedure), as well as running**
it with a more aggressive version of Pushup**, which as described in Section 3, re-expands all**
the nodes in the search branch, after an action has been pushed up. We can see that running AltAltp **with the** Pushup **and fattening procedures is better than just the latter. Comparison**
of results in Figure 15(a) and Figure 18(a) shows that even just the fattening procedure performs better than the original AltAlt**. In Figure 18(b) we can see that although the** Pushup **procedure does not add much overhead, the aggressive version of** Pushup **does get**
quite expensive. We also notice that only around 20 problems **are solved within time limits**
12. We also verified this with at least one problem in all the other domains.