Snakemake rule higher priority than all other rules

Question

So I know that in order to set rule priority, you use ruleorder. Is there an efficient way to give a rule priority over all other rules? For example, suppose I have rules a, b, and c. I would like rule b to have higher priority over a and c. How would I do this other than manually doing ruleorder: b > c and ruleorder: b > a?

Answer 1

One option is to specify rule-specific priority using priority directive:

rule a:
   priority: 100

The default priority for a rule is 0, so assigning any value greater than 0 will push the rule above the other rules that are ready for execution. Similarly, one can assign negative priority values, so a rule is executed last relative to other rules that are ready for execution.

The specific numeric value is not important, what is important is the relative ordering of the assigned priorities.