This section focuses on the interconnection network simulation.
The entities that form an interconnection network are:
switch: A switch decides the routing on a packet. Switches could be
input buffered or output buffered. The former are implemented as individual posers
per port of each switch while the latter are implemented as a poser per switch.
In an Input Buffered (IB) switch, a packet in a switch is stored at the input
port until its next route is decided and leaves the switch if it finds
available space on the next switch in the route.
While in an Output Buffered (OB) switch, a packet in a switch decides beforehand
on the next route to take and is buffered at the output port until space is
available on the next switch along the route.
Switches are modeled in much detail. Ports, buffers and
virtual channels at ports to avoid head-of-the-line blocking are
modeled. Hardware collectives are implemented on the switch to
enable broadcasts, multicasts and other collective operations
efficiently. These are configurable and can be used if the system
being simulated supports them. We also support configurable
strategies for arbitration, input virtual channel selection and output
virtual channel selection. The configurability of the switch
provides a flexible design, satisfying the requirements of
a large number of networks.
network card: Network cards packetize and unpacketize messages.
A NIC is implemented as two posers. The sending and receiving entities in a
NIC are implemented as separate posers. A NIC is attached to each node.
channel: These are modeled as posers and connect a NIC to a switch
or a switch to another switch.
compute node: Each compute node connects to a network interface card.
A compute node simulates execution of entry methods on it. It is also attached
to a message traffic generator, which is used when only an interconnection
network is being simulated. This traffic generator can generate any message
pattern on each of the compute nodes.
The traffic generator can send
point-to-point messages, reductions, multicasts, broadcasts and other
collective traffic. It supports k-shift, ring, bit-transpose,
bit-reversal, bit-complement and uniform random traffic.
These are based on common communication patterns found in
real applications. The frequency of message generation is determined
by a uniform or Poisson distribution.
