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Coding for Efficiency › Eliminating Unnecessary Records

Eliminating Unnecessary Records

Eliminating the most frequently occurring record first is most efficient. For example:

Elimination of the Most Frequent Record

                       A occurs 2,000 times
                       B occurs 1,000 times
                       C occurs 50 times

017    COMPANY EQ 'A'  DROP        (Tests 3,050 records, drops 2,000)
017    COMPANY EQ 'B'  DROP        (Tests 1,050 records, drops 1,000)
017    COMPANY EQ 'C'  DROP        (Tests    50 records, drops    50)
            4,150 tests required to drop all records.

                                or

Eliminating records randomly is least efficient. For example:

Elimination of Random Records

                       A occurs 50 times
                       B occurs 1,000 times
                       C occurs 2,000 times

017    COMPANY EQ 'A'  DROP        (Tests 3,050 records, drops    50)
017    COMPANY EQ 'B'  DROP        (Tests 3,000 records, drops 1,000)
017    COMPANY EQ 'C'  DROP        (Tests 2,000 records, drops 2,000)
            8,050 tests required to drop all records.