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T ABLE 8.4. Tradeoff of space against timeformethods A to G.
Method
Space
Time
(%)
(ms)
A
1.0
7,564.5
B
31.7
895.6
C
44.7
458.4
D
97.8
71.8
E
158.1
18.9
F
173.7
1.4
G
300.0
0.9
A
10000
1000
B
C
100
D
E
10
F
1
G
0
100
200
300
Space overhead (%)
F IGURE 8.4. Tradeoff of space against timeformethods A to G.The boxed
area to theright and aboveeach pointisofunacceptable performance: any
method in that areawill be less efficient with respect to both space andtime
than thepoint atthebox'scorner.
Fig. 11.7 Another table compared to a graph. The data shows how different methods compare
with respect to space and time. The table is difficult to interpret. The graph illustrates the frontier
of efficiency, that is, it describes the region (towards the bottom left ) that would represent an
improvement on existing methods
Where several methods of achieving the same aim are being illustrated, the axes in
each graph should have the same scale. For example, if you are comparing different
data structures and a separate graph is used for each one, the axes should be consistent
from one graph to the next. That is, if y , say, ranges from 0 to 80 on one graph, it
should also range from 0 to 80 on the other, to allow direct comparison between the
methods. Comparison is easier with several (but not too many) lines on one graph.
In general, for a quantity that is wholly positive and measured on a ratio scale
(where, say, a doubling in the measure corresponds to a doubling in the underlying
 
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