Jsun Yui Wong
The computer program listed below seeks to find integer solutions (if any) of the following nonlinear system, which is based on the nonlinear system of Problem 2.8 of Shoup [9, pages 40-41].
5 * X(1) + 3 * X(2) + X(3)+ X(4)=15,
X(1) * X(2) + X(2) * X(3) + X(3) * X(4)=17,
X(1) ^ 2 + X(2) ^ 2 + X(3) ^ 2 - X(4) ^ 2=9,
X(1) * X(3) + X(2) * X(4) + X(1) ^ 3=8.
0 DEFDBL A-Z
3 DEFINT J, K
4 DIM X(342), A(342), L(333), K(333)
12 FOR JJJJ = -32000 TO 32000
14 RANDOMIZE JJJJ
16 M = -1D+317
91 FOR KK = 1 TO 4
94 A(KK) = -500 + FIX(RND * 10001)
95 NEXT KK
128 FOR I = 1 TO 100000
129 FOR K = 1 TO 4
131 X(K) = A(K)
132 NEXT K
155 FOR IPP = 1 TO FIX(1 + RND * 3)
181 B = 1 + FIX(RND * 4)
182 IF RND < -.1 THEN 183 ELSE GOTO 189
183 R = (1 - RND * 2) * A(B)
186 X(B) = A(B) + (RND ^ 3) * R
188 GOTO 191
189 IF RND < .5 THEN X(B) = A(B) - FIX(1 + RND * 1.99) ELSE X(B) = A(B) + FIX(1 + RND * 1.99)
191 NEXT IPP
1001 X(4) = 15 - 5 * X(1) - 3 * X(2) - X(3)
1004 N96 = -17 + X(1) * X(2) + X(2) * X(3) + X(3) * X(4)
1111 N97 = -9 + X(1) ^ 2 + X(2) ^ 2 + X(3) ^ 2 - X(4) ^ 2
1116 N98 = -8 + X(1) * X(3) + X(2) * X(4) + X(1) ^ 3
1335 P = -ABS(N96) - ABS(N97) - ABS(N98)
1499 IF P <= M THEN 1670
1657 FOR KEW = 1 TO 4
1658 A(KEW) = X(KEW)
1659 NEXT KEW
1661 M = P
1670 NEXT I
1888 IF M < -1000 THEN 1999
1917 PRINT A(1), A(2), A(3), A(4), M, JJJJ
1999 NEXT JJJJ
This computer program was run with qb64v1000-win [10]. Copied by hand from the screen, the computer program’s complete output through JJJJ=-31985 is shown below:
1 1 4 3 0
-32000
1 1 4 3 0
-31999
1 1 4 3 0
-31996
3 -6 8 10 -20
-31995
1 1 4 3 0
-31994
1 1 4 3 0
-31992
1 1 4 3 0
-31990
2 -2 5 6 -15
-31988
11 -36 24 44 -272
-31986
1 1 4 3 0
-31985
Above there is no rounding by hand; it is just straight copying by hand from the screen.
On a personal computer with a Pentium Dual-Core CPU E5200 @2.50GHz, 2.50 GHz, 960 MB of RAM and with qb64v1000-win [10], the wall-clock time through
JJJJ=-31985 was 5 seconds, not including "Creating .EXE file..." time.
Acknowledgment
I would like to acknowledge the encouragement of Roberta Clark and Tom Clark.
References
[1] R. Burden, J. Faires, A. Burden, Numerical Analysis, Tenth Edition. Cengage Learning, 2016.
[2] R. Burden, J. Faires, Numerical Analysis, Sixth Edition. Brooks/Cole Publishing Company, 1996.
[3] R. Burden, J. Faires, Numerical Analysis, Third Edition. PWS Publishers, 1985.
[4] D. Greenspan, V. Casulli, Numerical Analysis for Applied Mathematics, Science, and Engineering. Addison-Wesley Publishing Company, 1988
[5] L. W. Johnson, R. D. Riess, Numerical Analysis, Second Edition. Addison-Wesley Publishing Company, 1982
[6] Microsoft Corp. BASIC, second edition (May 1982), Version 1.10. Boca Raton, Florida: IBM Corp., Personal Computer, P. O. Box 1328-C, Boca Raton, Florida 33432, 1981.
[7] William H. Mills, A System of Quadratic Diophantine Equations, Pacific Journal of Mathematics, 3 (1953), pp. 209-220.
[8] Terry E. Shoup, Applied Numerical Methods for the Microcomputer, Prentice-Hall, 1984.
[9] Terry E. Shoup, A Practical Guide to Computer Methods for Engineers, Prentice-Hall, 1979.
[10] Wikipedia, QB64, https://en.wikipedia.org/wiki/QB64.
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