Digital Signal Processing Reference
In-Depth Information
Incrementer
Incrementer
Fig. 10
Block diagram of the buffer used in the architecture
3.6
PE-CU-PE Interface Operation
Before resampling, the PE
i
computes and accumulates the weights of the particles
and sends its local sum of weights of
M
P
particles to the CU. Then the CU adds
P
sums of weights from all the PEs and returns the sum of weights of
M
particles,
sum
total
, back to each PE. Each PE normalizes the weights using sum
total
. The total
number of particles generated by the PE is approximately equal to the normalized
sum of weights.
The resampling process is started as each PE starts to send a particle and its
normalized weight to the CU. The interface between each PE and CU is shown in
Fig.
11
where
P
/
4 is assumed. When the CU receives a particle from PE
i
,itfirst
checks whether its weight (
r
=
t
) is zero. The particles are stored in the input FIFO
only if the weight is non-zero. At the output of the input FIFO, a particle is sent to
the split operator is also stored in TB
i
if it is tagged.
Before a particle is written to the memory, a particle split operation is performed
to have a particle with its replication factor larger than 1. Such a split operation
always reduces the replication factor of a particle whenever a particle is written to
a buffer except RTB
id
. Since it is very critical to redistribute particle among
P
PEs,
it is necessary that the largest replication factor of a particle must be less than or
equal to
M
,
P
. After a particle is split, a FIFO is used to buffer the output of the
split operator before it is written in a memory. Thus, when a particle is read from
any PE, the CU has to make sure that the maximum replication factor of a particle
is satisfied. This is accomplished by splitting a particle
S
times where
S
/
log
2
P
.
The split operation can be described as follows. When a replication factor is
larger than 1, it is divided by 2 (a simple shift operation is necessary). Then if the
least significant bit of a replication factor before the split operation is 0, then no
=
