Texas Instruments TI-89 Tip List page 339

Table 2 shows the time required to access a matrix element when the indices are local variables, for
example, matrix[m1,m2]. The data shows that it takes slightly longer to access an element with
variable indices, but the overhead for indirect access is about the same, at a mean of 5.8 mS.
Matrix dimensions
10 rows, 10 columns
20 rows, 20 columns
Table 3 shows the mean time required to access each element of matrices of various sizes. Element
indices are local variables, and the elements were accessed by value, for example, matrix[m1,m2].
Matrix Matrix
rows columns
5 25
5 35
5 45
5 55
5 65
5 75
5 85
5 95
5 105
5 115
5 125
5 135
5 145
5 155
10 10
10 20
10 30
10 40
[15,15] 27.8
[20,20] 32.7
Table 2
Matrix element access time, variable indices
Element Access time Tav,
accessed value method
(mS)
[1,1] 15.5
[5,5] 17.9
[10,10] 20.6
[1,1] 15.5
[5,5] 19.5
[10,10] 24.2
[15,15] 29.5
[20,20] 34.2
Table 3
Mean matrix element access time, direct access
Mean access time,
single element (mS)
18.9
19.7
20.9
21.4
22.5
23.6
25.0
25.9
27.0
27.9
28.9
30.1
31.3
32.4
18.2
20.3
22.6
24.9
33.3
38.2
Access time Tar,
reference method
(mS)
21.2
23.7
26.2
21.3
25.2
30.2
35.3
40.2
Matrix Matrix
rows columns
20 10
20 20
20 30
25 5
30 10
30 20
35 5
40 10
40 20
45 5
50 10
55 5
60 10
65 5
70 10
75 5
80 10
85 5
5.5
5.5
Reference method
overhead
Tar - Tav
5.7
5.8
5.6
5.8
5.7
6.0
5.8
6.0
Mean access time,
single element (mS)
21.5
25.5
29.3
19.1
23.8
30.0
21.2
25.2
34.0
21.9
27.7
23.6
30.3
25.0
32.9
26.0
35.4
27.4
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