2,428 research outputs found
Constructing Hierarchical Image-tags Bimodal Representations for Word Tags Alternative Choice
This paper describes our solution to the multi-modal learning challenge of
ICML. This solution comprises constructing three-level representations in three
consecutive stages and choosing correct tag words with a data-specific
strategy. Firstly, we use typical methods to obtain level-1 representations.
Each image is represented using MPEG-7 and gist descriptors with additional
features released by the contest organizers. And the corresponding word tags
are represented by bag-of-words model with a dictionary of 4000 words.
Secondly, we learn the level-2 representations using two stacked RBMs for each
modality. Thirdly, we propose a bimodal auto-encoder to learn the
similarities/dissimilarities between the pairwise image-tags as level-3
representations. Finally, during the test phase, based on one observation of
the dataset, we come up with a data-specific strategy to choose the correct tag
words leading to a leap of an improved overall performance. Our final average
accuracy on the private test set is 100%, which ranks the first place in this
challenge.Comment: 6 pages, 1 figure, Presented at the Workshop on Representation
Learning, ICML 201
Role of the effective payoff function in evolutionary game dynamics
In most studies regarding evolutionary game dynamics, the effective payoff, a
quantity that translates the payoff derived from game interactions into
reproductive success, is usually assumed to be a specific function of the
payoff. Meanwhile, the effect of different function forms of effective payoff
on evolutionary dynamics is always left in the basket. With introducing a
generalized mapping that the effective payoff of individuals is a non-negative
function of two variables on selection intensity and payoff, we study how
different effective payoff functions affect evolutionary dynamics in a
symmetrical mutation-selection process. For standard two-strategy two-player
games, we find that under weak selection the condition for one strategy to
dominate the other depends not only on the classical {\sigma}-rule, but also on
an extra constant that is determined by the form of the effective payoff
function. By changing the sign of the constant, we can alter the direction of
strategy selection. Taking the Moran process and pairwise comparison process as
specific models in well-mixed populations, we find that different fitness or
imitation mappings are equivalent under weak selection. Moreover, the sign of
the extra constant determines the direction of one-third law and risk-dominance
for sufficiently large populations. This work thus helps to elucidate how the
effective payoff function as another fundamental ingredient of evolution affect
evolutionary dynamics.Comment: This paper has been accepted to publish on EP
Influence of initial distributions on robust cooperation in evolutionary Prisoner's Dilemma
We study the evolutionary Prisoner's Dilemma game on scale-free networks for
different initial distributions. We consider three types of initial
distributions for cooperators and defectors: initially random distribution with
different frequencies of defectors; intentional organization with defectors
initially occupying the most connected nodes with different fractions of
defectors; intentional assignment for cooperators occupying the most connected
nodes with different proportions of defectors at the beginning. It is shown
that initial configurations for cooperators and defectors can influence the
stationary level of cooperation and the evolution speed of cooperation.
Organizations with the vertices with highest connectivity representing
individuals cooperators could exhibit the most robust cooperation and drive
evolutionary process to converge fastest to the high steady cooperation in the
three situations of initial distributions. Otherwise, we determine the critical
initial frequencies of defectors above which the extinction of cooperators
occurs for the respective initial distributions, and find that the presence of
network loops and clusters for cooperators can favor the emergence of
cooperation.Comment: Submitted to EP
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