each problem has a different makespan. The mean
values and standard deviations of
schedules are
presented in the figure 3. It takes about five weeks for
complete training and about 100 seconds to make
candidates of schedules.
The values derived by the proposed method
with/without convolution are better than a dispatching
method, even without training (number of times of
training is 0). Thus, it is likely that they find a good
schedule by making a lot of candidates, which is not an
effect of convolutions.
A result worth noting is that a value given by the
proposed method with convolutions improves with the
number of times of training and outperforms the one
without convolutions, which do not give the same
results. With number of times of training at
, we
achieve an 87 %, 95 %, or 97 % reduction in makespan
as compared to a dispatching method, where number
of times of training is 0, and the proposed method
without convolution. These differences are significant
as per the t-test, which gives 0.05. Therefore, we
consider that the proposed method can select an
appropriate allocation for each state of schedule-
making because the DNN can recognize the state of
making the schedule in detail as a result of
convolutions.
7 CONCLUSION
We study the DRL method for learning dispatching
rules automatically. Our contribution to the existing
literature is a new DNN model that can recognize both
numeric and nonnumeric information of schedule-
making by applying graph structure of a schedule and
a GCNN. Moreover, we reduce computational time of
the GCNN by applying a partial convolution. After
training a DNN using the DRL algorithm, we observed
that the value of a schedule made by the proposed
method for problems not used in training improves
with the number of times of training. Therefore, we can
automatically construct a good dispatching rule and
expect to reduce the work load for scheduling staff.
However, this paper shows that the proposed
method works on a restricted setting only. To use this
method in a practical scenario, additional experiments
and enhancements need to be conducted. First, the
proposed method should work on problems with a
scale of 1,000 operations. Second, the proposed
method should make a schedule subject to individual
constraints.
ACKNOWLEDGEMENTS
We would like to thank Editage (www.editage.com)
for English language editing.
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