Architectures for Particle Filtering - Signal Processing Systems - page 646

Fig. 15 Condition flags generator

There are two approaches in designing the overall exchange controller. One
approach is to connect “ALL” the PE CU interfaces at any given cycle. While
this can connect as many PE CU interfaces, the complexity of the controller is
prohibitive because of the enormous number of possible states. The second approach
is to connect “TWO” out of all the available PE CU interfaces at any given cycle.
The second approach, which is adopted in the mechanism, has a key benefit that
it has very low complexity comparing to that of the first approach. Moreover, the
controller is scalable where the only modification is on the priority decoder which
suggest the best pairing based on the conditions from the status generator and the
current activity of the PE CU interfaces.
The priority Decoder is extremely important to maximize the concurrency of all
the buffers so that the time it takes to transfer particles is minimized. Moreover, the
Priority Decoder is responsible to avoid a possible deadlock due to sharing buffers.
The Priority Decoder is ROM where the address of the ROM is set to flag SD i and the
activity condition of the PE CU i interface. The activity condition indicates whether
a particular PE CU i interface is currently participating in the particle transfer.
Thus based on these flags, final outputs suggesting the particle transfer topology
are generated. When considering a possible connection, the inter-connection has
a higher priority over intra-connection (i.e., particle transfers between different
PE CU interfaces have higher priorities). The output of the Priority Decoder is used
by the Exchange Controller for the actual particle transfer. The size of the ROM
depends on the number of PE employed.
At any given cycle, the Priority Decoder generates two sets of signals based
on the information which it received as inputs. They are S 1 and S 2 . These sets
of signals signify two PE CU interfaces in which the internal particle transfer is
to be performed. One restriction is that both interfaces indicated by these signals
cannot be sources and destinations. There are two cases for pairing. The source
and destination are in different PE CU interfaces and, the source and destination
are within the same PE CU interface. In the second case, we can establish two
simultaneous connections. To support these capabilities, S 1 and S 2 consist of
( s 1

, , ,

s 4 )where s 1 is an index of interface, s 2 indicates whether the connection is
intra (1) or inter (0), s 3 indicates whether the corresponding interface is a source (1)

s 2 s 3