Decision Support Tool for Design and Reliability Assessment of Water Distribution Networks - Pattern Recognition for Reliability Assessment of Water Distribution Networks - page 243

Table 9.2 Default boundary conditions for GA-optimisation of generated/filtered networks

Description EO-Optimizer

Objective function Least-cost diameter

Fitness Threshold pressure (20mwc)

Penalty For pressure < 20mwc, +200,000

The process starts by importing three types of files:
1. The generated/filtered INP-files ( name.inp ) whose names are specified in the
accompanying EPAinpfiles.txt file.
2. The TXT-files stored in the Inp.txt file that have been generated in case the GA
optimisation setting has been selected in the network generation module. Each TXT-file
labelled as SNxxx.txt , xxx being the serial number, contains the EPANET input filename,
with INP and RPT extension, followed by the total number of links, and their IDs, and
finally the total number of nodes, followed by the node ID.
3. The file GApara_sample.txt which contains the definition of GA-parameters: population
size, selection type, total generation number and GA-operators (crossover and mutation
rates). Based on the information in this file, each network will automatically receive the
file SNxxx_GApara.txt with its own settings based on its own size i.e. number of links.

The default GA-parameters applied for optimization in this module are shown in Table 9.3.

Table 9.3 Default GA-optimisation parameters

Description GA parameters

Vector size 20~200

Population size 100

Maximum no. of generations 5,000

No. of generations with no improvement 3,500

Selection Tournament

Crossover probability 0.55

Mutation probability 0.4 ~ 0.45

The list of diameters available for optimisation can be created in three ways: (1) by
specifying continuous range, (2) by specifying a range and the diameter increment, and (3) by
specifying the number of specific diameters manually. The latter is the option closest to the
reality, while the first one is the fastest and the most accurate one in view of targeting the
threshold pressure. The final output from the simulation is (a sequence of) optimised INP-
file(s) coded as Y_Optimized_name.inp . Based on the above selection of diameters, Y can
assign C (for continuous D ), I (for incremental D ) or M (for manual D ).