Original vs SPT

Total Completion Comparison

Comparing totals shows how much the SPT sequence improves the simple objective.

highlighted = computed this step

Original total

Original total completion time is 13.

original=13\text{original}=13
Original and SPTThe chart shows both sequences and the completion table.sequence comparisonimprovement 3OriginalA p=3C=3B p=1C=4C p=2C=606SPTB p=1C=1C p=2C=3A p=3C=606completion tablejoboriginal CSPT CA36B41C63totals 13 -> 10averages 13/3 -> 10/3

SPT total

SPT total completion time is 10.

SPT=10\text{SPT}=10
Original and SPTThe chart shows both sequences and the completion table.sequence comparisonimprovement 3OriginalA p=3C=3B p=1C=4C p=2C=606SPTB p=1C=1C p=2C=3A p=3C=606completion tablejoboriginal CSPT CA36B41C63totals 13 -> 10averages 13/3 -> 10/3

Improvement

The improvement is 3.

improvement=3\text{improvement}=3
Original and SPTThe chart shows both sequences and the completion table.sequence comparisonimprovement 3OriginalA p=3C=3B p=1C=4C p=2C=606SPTB p=1C=1C p=2C=3A p=3C=606completion tablejoboriginal CSPT CA36B41C63totals 13 -> 10averages 13/3 -> 10/3

Why SPT helps

Short jobs finish earlier, so they stop adding to the total completion-time sum.

short jobs finish earlier\text{short jobs finish earlier}
Original and SPTThe chart shows both sequences and the completion table.sequence comparisonimprovement 3OriginalA p=3C=3B p=1C=4C p=2C=606SPTB p=1C=1C p=2C=3A p=3C=606completion tablejoboriginal CSPT CA36B41C63totals 13 -> 10averages 13/3 -> 10/3