systolic array

systolic array

   <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.

   See also {Ruby}, {SISAL}.

   (1998-07-01)