Reassigning array values in for loop

2022 4 28
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更新时间：2022 4 28
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I want to make a random number generator. It uses 3 formulas so I have 3 arrays which will store the values that are generated.
I currently have a for loop that generates the numbers but for some reason it is not updating the arrays. I tested the formulas by writing specific values for n and it does work so the problem seems to be in the loop.
Can anyone see why it is not working?
a1 = 0; a2 = 63308; a3 = -183326;
b1 = 86098; b2 = 0; b3 = -539608;
m1 = 2147483647; m2 = 2145483479;
%create an array with 10000 spaces
Z = zeros(1,10000);
X = zeros(1,10000);
Y = zeros(1,10000);
%To compute the random numbers, I need a seed for x and y
X(1) = 1; X(2) = 4; X(3) = 11;
Y(1) = 2; Y(2) = 9; Y(3) = 17;
x_n = @(n) mod((a1*X(n-1) + a2*X(n-2) + a3*X(n-3)),m1);
y_n = @(n) mod((b1*Y(n-1) + b2*Y(n-2) + b3*Y(n-3)),m2);
z_n = @(n) mod((x_n(n) - y_n(n)),m1);
for i=4:10000
X(i) = x_n(i);
Y(i) = y_n(i);
Z(i) = z_n(i);
end
disp(Z)

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dpb
dpb 2022-4-28
>> [X(1:10);Y(1:10);Z(1:10)]
ans =
1 4 11 69906 2.1474e+09 2.1455e+09 0 0 0 0
2 9 17 3.8445e+05 2.1406e+09 2.1363e+09 0 0 0 0
0 0 0 2.1472e+09 6.8197e+06 9.1569e+06 0 0 0 0
>>
Seems to do something for the variables you've calculated -- your loop only iterates over 4:6 so nothing other than those values can change.
Michelle Lear
Michelle Lear 2022-4-28
Oh, I had changed it to see if it would change a few but even when it's i=4:10000, it doesnt update for me. But I see it updates on yours, so maybe it's an error on my laptop

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David Hill
David Hill 2022-4-28

0 个投票

You are overflowing floating point numbers.
import java.math.*
a1 = BigInteger('0'); a2 = BigInteger('63308'); a3 = BigInteger('-183326');
b1 = BigInteger('86098'); b2 = BigInteger('0'); b3 = BigInteger('-539608');
m1 = BigInteger('2147483647'); m2 = BigInteger('2145483479');
%To compute the random numbers, I need a seed for x and y
X(1:3)=[BigInteger('1'),BigInteger('4'),BigInteger('11')];
Y(1:3) =[BigInteger('2'),BigInteger('9'),BigInteger('17')];
x_n = @(n) a1.multiply(X(n-1)).add(a2.multiply(X(n-2))).add(a3.multiply(X(n-3))).mod(m1);
y_n = @(n) b1.multiply(Y(n-1)).add(b2.multiply(Y(n-2))).add(b3.multiply(Y(n-3))).mod(m2);
z_n = @(n) x_n(n).subtract(y_n(n)).mod(m1);
for i=4:10000
X(i) = x_n(i);
Y(i) = y_n(i);
Z(i) = z_n(i);
end

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