the national character of their actions and
relationships with other agents. Other agents have an
insignificant market share, that being said, the
networks are led by market leaders. Therefore,
increasing the number of agents will simply lead to a
significant increase in complexity, without providing
any significant improvement in forecast accuracy.
Per contra one must note that agent-based models
should also directly or indirectly consider the other
party of the market relations – the consumers. In the
latter case, the impact of consumers is considered
indirectly, mainly due to the lack of reliable data on
the dynamics of fuel consumption by individual
market players.
One of the conditions for proper functioning of
the neural network the stationarity of the input and
output data. However, studies show that retail prices
in the petroleum product are far from stationary.
This makes it impossible to use absolute price value
for input prices of the neural network. Having
analyzed the growth of retail prices thus as seen in
Table 1 the increment of the retail price is of the
first order, hence allowing us price surges as inputs
for the neural network.
Table 1: Assessment of stationarity of the retail prices and
their increments.
Temporal series
Dickey-
Fuller
p-value
Retail prices for gasoline A-95 in
the period 2010-2014
2,211 0,49
Growth rate of retail gasoline
prices in the period 2010-2014
-7.921 0,01
It is also important to consider lags related to
purchasing and selling the products. If we ignore lag
compensation this will lead to inconsistencies
between the value of net costs relative to the that of
the selling price. To compensate for the lag in
calculating the margin, we use the following current
lag cost determination algorithm:
Choose date t
0
with a stable wholesale price
t = t
0
lag[t] = L_typ
while t < t_cur
lag[t] = f_LAG((t-lag[t-1])..t)
if lag[t] - lag[t-1] > 1
lag[t] = lag[t-1] + 1
t = t + 1
end
The following algorithm is used to determine lag,
calculated separately for each network at a certain
period of time using the formula below:
lagtt
typ
PP
a
LLAGf
100
;min_
where P
t-lag
– is the price at the beginning of the
period, P
t
– is the price at the end of the period, L
typ
– is the default lag value for stable market
conditions. Indicators a and γ are evaluated
separately for each of the agents on the , based on
the analysis of the price surges and behaviour of the
market entities.
The cost is not only used for calculating the
margin, but is also used in a rule that limits the
behavior of the network: the selling price cannot be
lower than the cost of production. Under standard
conditions this rule is practically never used, but at
times of significant volatility of incoming data it
generally minimizes risk of experiencing situations
with delay in model response for the surges of
inputted data.
All incoming threat-related information is
assigned not only a class, but also a threat rank,
which corresponds to the threat level for the market.
In this study we have identified the following threat
ranks:
-2 – a significant impact on the market towards a
drop in prices;
-1 – a moderate impact on the market towards a
drop in prices;
0 – no impact on the market is observed;
1 – a moderate impact on the market towards a
hike in prices;
2 – a significant impact on the market towards a
hike in prices.
Taking into account the price formulation factors
shown above, Figure 2 depicts the structure of the
neural network and the interpretation of the input. It
was found that the best form of neural networks for
solving this problem is a multilayer perceptron with
4 hidden layers. At the core of this network is a
fully-connected multilayer perceptron (layers 2-6).
The first layer has the activation ReLU (Rectified
Linear Unit) function and is intended to form linear
combinations of input. During the learning process it
generates indicators, based on which the retail
network acquires a behavioral classification. Unlike
the linear activation function, ReLU can reduce the
number of neurons per layer thanks to its non-linear
nature. Output has no activation function, but is
rather used as a multiplexer of the perceptron’s
output layer of price growth for the next time period.
Such network structure is dictated primarily by the
specificity of the input and output data.
About categorized under threat of impact forces
form the index of informational load. This index is
the sum of ranks of active threats at a time. This
approach takes into account both direct and indirect
impacts on the market with the formation of the