Performing a rooted-v collective operation by an operational group of compute nodes in a parallel computer includes: upon encountering a rooted-v collection operation during execution, identifying, by a root node of an operational group of compute nodes, a count to use for the selection of a collective algorithm for effecting the rooted-v collective operation; broadcasting, by the root node to the other computer nodes in the operational group, an active message, wherein the active message includes the identified count to use for the selection of the collective algorithm; and selecting, by all the compute nodes of the operational group based on the identified count, a same collective algorithm to effect the rooted-v collective operation; and executing the rooted-v collective operation by all compute nodes of the operational group using the selected algorithm.