Spectrum Computation by Means of the Logistics Computer 



The problem was eventually run on the Logistics Computer, owned by 

 the Office of Naval Research and operated by the George Washington Univer- 

 sity Logistics Research Project. Time was made available by ONR. This 

 computer is a plugboard controlled electronic digital computer with a large 

 internal drum memory of approximately 175,000 decimal digits. For this com- 

 putation a word length of 1 2 decimal digits (in reality 11 1/2, since negative 

 numbers are represented by 9'3 complements) was used, providing over 

 14,000 words of raemory, more than enough to store all the necessary data at 

 each stage of computation. 



The leveled data N-'j^ were provided on punched cards for both data sets 

 2 and 3. A later connputation was made on Data Set 2A derived from Data Set 2 

 by the deletion of all j from 50 to 59 and all k from to 19 inclusive, pro- 

 viding a 50 X 70 array; and on Data Set 3C derived from Data Set 3 by the de- 

 letion of all j from to 9 and 50 to 59, inclusive, providing a 40 x 90 array. 

 The N^, were converted from cards to paper tape-. Conversion and input were 

 checked by comparing Z) N-,, on the drum with a check sum of the punched 



j-k 



Jk 



cards. As eacL value of Q(p, q)(90 -lq|)(60 - p) was comiputed, it was punched 

 out on paper tape, ready for further input. Total computation time for Data 

 Sets 2 and 3 was about 30 hours apiece, each computation involving 3,433,500 

 multiplications and 6,867,000 drum references. For Sets 2A and 3C the 

 computation time v/as about 18 hours each. The computer was allowed to run 

 overnight unattended without encountering too many difficulties. Due to lack 



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