<architecture, parallel> (By analogy with the regular pumping
of blood by the heart) An arrangement of processors in an
array (often rectangular) where data flows synchronously
across the array between neighbours, usually with different
data flowing in different directions. H. T. Kung and Charles
Leiserson publish the first paper describing systolic arrays
in 1978 [reference?].

Each processor at each step takes in data from one or more
neighbours (e.g. North and West), processes it and, in the
next step, outputs results in the opposite direction (South
and East).

An example of a systolic algorithm might be matrix
multiplication. One matrix is fed in a row at a time from the
top of the array and is passed down the array, the other
matrix is fed in a column at a time from the left hand side of
the array and passes from left to right. Dummy values are
then passed in until each processor has seen one whole row and
one whole column. At this point, the result of the
multiplication is stored in the array and can now be output a
row or a column at a time, flowing down or accross the array.