Re: Cobol picture data (Thomas F. Reid)
Thu, 23 Apr 1992 16:29:41 GMT

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Newsgroups: comp.compilers
From: (Thomas F. Reid)
Keywords: Cobol
Organization: VPI&SU Computer Science Department, Blacksburg, VA
References: 92-04-099 92-04-109
Date: Thu, 23 Apr 1992 16:29:41 GMT

>(Say what you will about efficiency, but it's a language for data base
>operations. I/O is the bottleneck. Although for non-I/O-bound
>operations, it's reeaalllyyy ssllooww.)

Don't be so quick to assume that. In the mid 1980s, a project I worked on
analyzed a well-known-DBMS in search of performance improvements in very
large databases. Initial investigations showed that the DBMS was CPU
bound - 87-93% on a standalone VAX 11/780. Caching the indices in a 32 MB
ram disk brought very little improvement. So we put a monitor on it to
discover in what subroutines it was spending most of its time. A
significant number of them were conversion routines. It seemed that in
order to have a null value, they used binary zeroes in their BCD numbers
and non-null numbers had their digits increased by one. Thus, to perform
A + B, they had to subtract one from each digit of both A and B, perform
the addition, and then add one to each digit to store it. Microcoding the
worst 50 or so routines brought over a 50% impovement.

Tom Reid

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