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I am trying to adopt the D-optimal design for 8 attributes with 3 choices.
I get an "out of memory" error when I run the following code:

Design
;alts = alt1, alt2
;rows = 27
;orth = ood
;model:
U(alt1) = b1 + b2 * A[1, 2, 3] + b3 * B[1, 2, 3] + b4 * C[1, 2, 3] + b5 * D[1, 2, 3]
+ b6 * E[1, 2, 3] + b7 * F[1, 2, 3] + b8 * G[1, 2, 3] + b9 * H[1, 2, 3] /
U(alt2) = b2 * A + b3 * B + b4 * C + b5 * D
+ b6 * E + b7 * F + b8 * G + b9 * H
$

Changing the number of attributes to 7 or 10 will not cause the above error.
How do I avoid errors with the eight attributes?

Thank you.

The current implementation of optimal orthogonal designs use the matrix structures proposed by Street & Burgess & Louviere and these matrices can become extremely large when the number of attributes and/or alternatives are large, occassionally resulting in an "out of memory" message. The new version of Ngene, to be released later this year, has an entirely new algorithm to determine these optimal orthogonal designs and will not require the generation of large matrices.

Below is the design you are looking for, which was generated using the new algorithm.

Choice situation alt1.a alt1.b alt1.c alt1.d alt1.e alt1.f alt1.g alt1.h alt2.a alt2.b alt2.c alt2.d alt2.e alt2.f alt2.g alt2.h
1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2
2 1 3 3 2 2 2 1 2 2 0 0 3 3 3 2 3
3 1 2 2 3 3 3 1 3 2 3 3 0 0 0 2 0
4 3 3 2 2 2 1 2 1 0 0 3 3 3 2 3 2
5 3 2 1 3 3 2 2 2 0 3 2 0 0 3 3 3
6 3 1 3 1 1 3 2 3 0 2 0 2 2 0 3 0
7 2 2 3 3 3 1 3 1 3 3 0 0 0 2 0 2
8 2 1 2 1 1 2 3 2 3 2 3 2 2 3 0 3
9 2 3 1 2 2 3 3 3 3 0 2 3 3 0 0 0
10 3 2 2 2 1 2 1 1 0 3 3 3 2 3 2 2
11 3 1 1 3 2 3 1 2 0 2 2 0 3 0 2 3
12 3 3 3 1 3 1 1 3 0 0 0 2 0 2 2 0
13 2 1 3 3 2 2 2 1 3 2 0 0 3 3 3 2
14 2 3 2 1 3 3 2 2 3 0 3 2 0 0 3 3
15 2 2 1 2 1 1 2 3 3 3 2 3 2 2 3 0
16 1 3 1 1 3 2 3 1 2 0 2 2 0 3 0 2
17 1 2 3 2 1 3 3 2 2 3 0 3 2 0 0 3
18 1 1 2 3 2 1 3 3 2 2 3 0 3 2 0 0
19 2 3 3 3 1 3 1 1 3 0 0 0 2 0 2 2
20 2 2 2 1 2 1 1 2 3 3 3 2 3 2 2 3
21 2 1 1 2 3 2 1 3 3 2 2 3 0 3 2 0
22 1 2 1 1 2 3 2 1 2 3 2 2 3 0 3 2
23 1 1 3 2 3 1 2 2 2 2 0 3 0 2 3 3
24 1 3 2 3 1 2 2 3 2 0 3 0 2 3 3 0
25 3 1 2 2 3 3 3 1 0 2 3 3 0 0 0 2
26 3 3 1 3 1 1 3 2 0 0 2 0 2 2 0 3
27 3 2 3 1 2 2 3 3 0 3 0 2 3 3 0 0

Regards,
Michiel

Thank you for a very kind answer.
If you don't mind, I would like to know about the design and D-error when rows = 18.
Thank you and best regards,

An orthogonal design with 18 rows does not exist, the smallest orthogonal design has 27 rows.

Michiel

Thank you very much for your quick response.