Optimized data communications in a parallel computer

A method of optimized data communications in a parallel computer, the parallel computer comprising a plurality of compute nodes, each compute node comprising a network adapter, the network adapters coupling the compute nodes in a multi-dimension point-to-point network for data communications, each network adapter supporting communications in opposite directions of each dimension, the method comprising:

• receiving, by a network adapter of a receiving compute node, a data communications packet from a source direction of a source dimension, the packet specifying a compute node as a destination of the packet and specifying one or more deposit hints, each separate deposit hint associated uniquely with a direction of a dimension of the point-to-point network and each deposit hint indicating that the packet is to be deposited at each compute node in the associated direction on a path to the destination compute node;
• if a deposit hint indicates that the packet is to be deposited at compute nodes in the opposite direction of the source direction in the source dimension:
• delivering, by the network adapter, the packet to an application executing on the receiving compute node;
• forwarding the packet to a next compute node in the opposite direction of the source dimension only if the packet does not specify the receiving compute node as the destination of the packet;
• and
• forwarding the packet to a next compute node in a direction of a subsequent dimension only if the deposit hints indicate that the packet is to be deposited at compute nodes in the direction of the subsequent dimension.