  The approximation ratio of the longest processing time (LPT) scheduling
algorithm has been studied in several papers. While the tight approximation
ratio is known for the case when all processors are identical, the ratio is not
yet known when the processors have different speeds. In this work, we give a
tight approximation ratio for the case when the number of processors is 3,4,
and 5. We show that the ratio for those cases are no more than the lower bound
provided by Gonzalez, Ibarra, and Sahni (SIAM J. Computing 1977). They are
approximately 1.38 for three processors, 1.43 for four processors, and 1.46 for
five processors.
