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Method K=12 K=15 K=18 |
random search (N=36) 0.460 0.498 0.533 |
greedy classification (N=36) 0.602 0.624 0.641 |
greedy selection [30] (N=36) 0.618 0.637 0.647 |
VAS (N=36) 0.736 0.744 0.767 |
random search (N=64) 0.389 0.405 0.442 |
greedy classification (N=64) 0.606 0.612 0.618 |
greedy selection [30] (N=64) 0.612 0.618 0.626 |
VAS (N=64) 0.724 0.738 0.749 |
Table 19: ESR comparisons for the ship target class on the |
DOTA dataset. |
Method K=12 K=15 K=18 |
random search (N=36) 0.491 0.564 0.590 |
greedy classification (N=36) 0.602 0.629 0.657 |
greedy selection [30] (N=36) 0.609 0.638 0.665 |
VAS (N=36) 0.757 0.764 0.776 |
random search (N=64) 0.334 0.379 0.417 |
greedy classification (N=64) 0.524 0.541 0.559 |
greedy selection [30] (N=64) 0.531 0.552 0.576 |
VAS (N=64) 0.700 0.712 0.733 |
The results are presented in Tables 18 and 19, and |
are broadly consistent with our observations on the xView |
dataset, with VAS outperforming all baselines by ∼16–25%, |
with the greatest improvement typically coming on more |
difficult tasks (small Kcompared to N). |
G. Search Performance Comparison with |
Other Policy Learning Algorithm (PPO) |
We conduct experiments with other policy learning algo- |
rithm, such as PPO. With PPO [23], the idea is to constrain |
our policy update with a new objective function called the |
clipped surrogate objective function that will constrain the |
policy change in a small range [1−ϵ,1+ϵ]. Here, ϵis a |
hyperparameter that helps us to define this clip range. In |
all our experiment with PPO, we use clip range ϵ=0.2 |
as provided in the main paper [23]. We keep all other hy- |
perparameters including policy architecture fixed. We call |
14 |
the resulting policy VAS-PPO . In table 20, 21 we present |
the result of V AS-PPO and compare the performance with |
V AS. our experimental finding suggests that PPO doesn’t |
yield any extra benefits in spite of having added complexity |
overhead due to the clipped surrogate objective. |
Table 20: ANT comparisons with different policy learning algo- |
rithm for the small car target class on xView. |
Method C=25 C=50 C=75 |
VAS-PPO (N=30) 4.15 6.82 9.16 |
VAS (N=30) 4.61 7.49 9.88 |
VAS-PPO (N=48) 4.03 6.87 9.02 |
VAS (N=48) 4.56 7.45 9.63 |
Table 21: ANT comparisons with different policy learning algo- |
rithm for the large vehicle target class on DOTA. |
Method C=25 C=50 C=75 |
VAS-PPO (N=36) 4.01 6.24 7.56 |
VAS (N=36) 4.63 6.79 8.07 |
VAS-PPO (N=64) 4.89 7.93 10.12 |
VAS (N=64) 5.33 8.47 10.51 |
H. Sensitivity Analysis of VAS |
We further analyze the behavior of VAS when we inter- |
vene the outcomes of past search queries oin the following |
ways: (i) Regardless of the “true” outcome, we set the query |
outcome to be “unsuccessful” at every stage of the search |
process and observe the change in exploration behavior of |
VAS, as depicted in fig 10, 11, 12. (ii) Following a similar |
line, we also enforce the query outcome to be “successful” |
at each stage and observe how it impacts in exploration be- |
havior of VAS, as depicted in fig 10, 11, 12. |
Early V AS steps are similar between strictly positive and |
strictly negative feedback scenarios. This is due to the grid |
prediction network’s input similarity in early stages of V AS. |
The imagery and search budget are constant between the |
two, and the grid state vector between the two are mostly |
the same (as they are both initialized to all zeros). Follow- |
ing from step 7 we see V AS diverge. A pattern that emerges |
is that when V AS receives strictly negative feedback, it be- |
gins to randomly explore. After every unsuccessful query, |
V AS learns that similar areas are unlikely to contain objects |
of interest and so it rarely visits similar areas. This is most |
clear in figure 12 where we see at step 11 it explores an |
area that’s completely water. It then visits a distinctive areathat’s mostly water but with land (and no harbor infrastruc- |
ture). In strictly positive feedback scenarios we see V AS |
aggressively exploit areas that are similar to ones its already |
seen, as those areas have been flagged as having objects of |
interest. Consider the bottom row for each of figures 10, |
11, and 12. In figure 10, after a burn in phase we see V AS |
looking at roadsides starting in step 9. In figure 11, V AS |
seeks to capture roads. By step 15, V AS has an elevated |
probability for nearly the entire circular road in the upper |
left of the image. In figure 12, V AS seeks out areas that |
look like harbors. Together these examples demonstrate a |
key feature of reinforcement learning: the ability to explore |
and exploit. Additionally, they show that V AS is sensitive |
to query results and uses the grid state to guide its search. |
In fig 13, 14, 15, we provide a similar visualization of V AS |
under Manhattan distance based query cost. |
I. Efficacy of TTA on Search Tasks involving |
Large Number of Grids |
We conduct experiments with number of grids Nas |
900. We train V AS using small car as target while eval- |
uate with building as target class. We report the result |
in table 22. We observe a significant improvement (up to |
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