Spaces Places Species
Arvind Elango
Soma Vemulapalli
Bill Baykan
Terry Harrison
Introduction
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Digital Libraries
Want data survivability in a networked
environment (redundancy, distribution)
How to load the system with documents?
Model
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Species - asexual single-cell organism (record)
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Places or Islands (servers)
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Spaces (amount of room for organisms)
Goal
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To find a method of evaluating the carrying
capacity of various configured systems to
provide maximum survivability
Parameters
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Local comfort
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Global comfort
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Number of “Spaces” - islands
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Number of “Places” - room on each island
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Number of unique “Species”
Population Rules (for each island)
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Each species introduced will seek to achieve the predetermined
local and exceed the global comfort level
(ie 2 per island/ 50% of islands)
A new species may replicate itself on the island if empty places
are available (ie 11x | 11x| 11x ---> 222 | 112 | 112)
A new species may replace a duplicate of another species on an
island (ie 112 ---> 312) there is still one 1 present
A new species may replace a member of another species if the
other species is above its global comfort level
( ie 222 | 112 | 112 ---> 333 312 112)
Population Example
___ ___ ___
1 1 0
2 2 2
3 3 3
___ ___ ___
1 1 0
1 1 2
3 1 2
Local comfort
=2
Global comfort
= 50%
Number of species = 3
Number of space = 3
Number of islands = 3
___ ___ ___
1 1 0
1 1 2
3 1 2
Modeling -Disturbance Phase
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System disruptions shall be simulated by the
random deletion of islands followed by the
creation of a new island
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Balancing follows
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100 iterations per test load
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Passes if no extinctions
Test 1
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Number of places fixed at 5
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Local comfort = 2
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Global comfort = 30%
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Determine how carrying capacity changes as
number of islands is increased
Test 2
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Number of places fixed at 10
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Local Comfort = 2
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Global Comfort set to 30%
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Determine how carrying capacity changes as
number of islands is increased
Test 3 (Varying global comfort)
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Number of places = 5
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Local comfort = 2
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Global comfort = 10%,30%,50%
(paranoia knob)
Determine how carrying capacity changes as
number of islands is increased
Results
The stability of the system is reasonably high when
the number of species, spaces and places are equal.
Spaces vs Species
25
22.5
No. of Species
20
17.5
15
5 Islands
10 Islands
12.5
10
7.5
5
2.5
0
1
2
3
4
5
6
7
No. of Spaces
8
9
10
20
No. of Species
Species vs Island
14
13
12
11
10
9
8
7
6
5
5 spaces
10 spaces
4
3
2
1
0
1
2
3
4
5
6
7
8
9
No. of Islands
10
20
30
40
Conclusions
With a constant number of islands, the number of species which
can be maintained increases linearly with the number of spaces.
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With a fixed number of spaces, the carrying capacity increases up
to a certain number of islands (depending upon the algorithm and
the global comfort level) and then saturates. This observation
needs to be analyzed further.
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Future Possibilities
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Tuning “Paranoia knob” of individual species
Self adjusting “knob” in response to network
threat (on both system/species level)