斐波那契移位寄存器伪随机数发生器

Question

我正在尝试让下面的代码在斐波那契移位寄存器上工作，以生成伪随机数。似乎不能让它工作，那么()有什么明显的问题(？)

Shared Function Main() As Integer
    Dim start_state As UShort = &HACE1UI ' Any nonzero start state will work.
    Dim lfsr As UShort = start_state
    Dim bit As UInteger
    Dim period As UInteger = 0

    Do While lfsr <> start_state
        ' taps: 16 14 13 11; feedback polynomial: x^16 + x^14 + x^13 + x^11 + 1 
        bit = ((lfsr >> 0) Xor (lfsr >> 2) Xor (lfsr >> 3) Xor (lfsr >> 5)) And 1
        lfsr = (lfsr >> 1) Or (bit << 15)
        period += 1
    Loop 

    Return 0
End Function

最后，"period“是否需要除以一个大整数才能得到U(0，1)？

以下是原始的C++代码：

# include <stdint.h>
int main(void)
{
    uint16_t start_state = 0xACE1u;  /* Any nonzero start state will work. */
    uint16_t lfsr = start_state;
    uint16_t bit;                    /* Must be 16bit to allow bit<<15 later in the code */
    unsigned period = 0;

    do
    {
        /* taps: 16 14 13 11; feedback polynomial: x^16 + x^14 + x^13 + x^11 + 1 */
        bit  = ((lfsr >> 0) ^ (lfsr >> 2) ^ (lfsr >> 3) ^ (lfsr >> 5) ) & 1;
        lfsr =  (lfsr >> 1) | (bit << 15);
        ++period;
    } while (lfsr != start_state);

    return 0;
}

Answer 1

就像@dummy的评论一样，

Do While lfsr <> start_state
...
Loop

不会运行，因为一开始就是lfsr = start_state。

相当于C++的代码

do {
...
} while (lfsr != start_state);

在VB.NET中是

Do
...
Loop While lfsr <> start_state