PROCESS FOR DETERMINING CYCLES REPLACEABLE BY VECTOR COMMANDS OF A VECTOR COMPUTER INSIDE COMMAND LOOPS OF PROGRAMS WRITTEN FOR VON NEUMANN COMPUTERS

摘要

When programs written for Von Neumann computers can be used on giant computers, for example vector computers, the program operations that can be executed in parallel must be executed in parallel in vector computers in order to exploit the capacity of these last. These situations can then be introduced into the program if it contains program loops. A program loop that does not contain any cycles can be vectorized, that is, executed by vector instructions. If a program loop has cycles, the vector computer must have special instructions for running these cycles in parallel. A special instruction of this type can, for example, be an instruction to form the vector sum or to form an arithmetic series. The instruction loops are checked for the presence of any cycles which can be replaced by special instructions. For this purpose, the control flow and the data flow determined by the instructions in the loop are analyzed and control correlations and data correlations between the scalar occurrences of variables in the instructions are determined and plotted on a graph. We then carefully analyze this graph to determine whether a cycle it contains can be replaced by a vector instruction from the vector computer.