blocks|key|1497458|text|我从GNU+C库中拿了一个，源代码可以在线浏览。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1497459|http://qa.coreboot.org/docs/libpayload/rand_8c-source.html|offset|length|1497460|但是，如果您对随机数的质量有任何顾虑，您可能应该查看更仔细编写的数学库。这是一个很大的话题，标准的rand实现并没有得到专家的高度重视。|style|CODE|1497461|这里有另一种可能性：http://www.boost.org/doc/libs/1_39_0/libs/random/index.html|1497462|(如果你发现你有太多的选择，你总是可以随机选择一个。)|1497463|entityMap|0|LINK|mutability|MUTABLE|url|1|http://www.boost.org/doc/libs/1_39_0/libs/random/index.html^0|0|0|1M|0|0|1D|4|0|A|1N|1|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@$D|Y|E|Z|1|10]]|A|$]]|$1|F|3|G|5|6|7|11|8|@$D|12|E|13|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|14|8|@]|9|@$D|15|E|16|1|17]]|A|$]]|$1|L|3|M|5|6|7|18|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|O|$P|$5|Q|R|S|A|$T|C]]|U|$5|Q|R|S|A|$T|V]]]]

I'd take one from the GNU C library, the source is available to browse online.

<a href="http://qa.coreboot.org/docs/libpayload/rand_8c-source.html" rel="nofollow noreferrer">http://qa.coreboot.org/docs/libpayload/rand_8c-source.html</a>

But if you have any concern at all about the quality of the random numbers, you should probably look at more carefully written mathematically libraries. It's a big subject and the standard <code>rand</code> implementations aren't highly thought of by experts.

Here's another possibility: <a href="http://www.boost.org/doc/libs/1_39_0/libs/random/index.html" rel="nofollow noreferrer">http://www.boost.org/doc/libs/1_39_0/libs/random/index.html</a>

(If you find you have too many options, you could always pick one at random.)

blocks|key|1282719|text|这里有一个指向ANSI+implementation+of+a+few+random+number+generators的链接。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1282720|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cs.wm.edu/~va/software/park/park.html^0|C|1C|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Here is a link to a ANSI C <a href="http://www.cs.wm.edu/~va/software/park/park.html" rel="nofollow noreferrer">implementation of a few random number generators</a>.

blocks|key|1282749|text|标准的解决方案是使用linear+feedback+shift+register。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1282750|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Linear_feedback_shift_register^0|A|U|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

The standard solution is to use a <a href="http://en.wikipedia.org/wiki/Linear_feedback_shift_register" rel="nofollow noreferrer">linear feedback shift register</a>.

blocks|key|1497549|text|看看这篇来自George+Marsaglia的collection+of+random+number+generators。他是一位领先的随机数生成专家，所以我对他推荐的任何东西都很有信心。该列表中的生成器很小，一些生成器只需要几个无符号的长整型作为state。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1497550|Marsaglia的发电机绝对是“高质量”的，按照你的标准，周期长，分布均匀。它们通过了严格的统计测试，尽管它们不适用于密码学。|1497551|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cse.yorku.ca/~oz/marsaglia-rng.html^0|N|12|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

Check out this <a href="http://www.cse.yorku.ca/~oz/marsaglia-rng.html" rel="noreferrer">collection of random number generators</a> from George Marsaglia. He's a leading expert in random number generation, so I'd be confident using anything he recommends. The generators in that list are tiny, some requiring only a couple unsigned longs as state.

Marsaglia's generators are definitely "high quality" by your standards of long period and good uniform distribution. They pass stringent statistical tests, though they wouldn't do for cryptography.

blocks|key|1497584|text|我推荐David+Carta的学术论文Two+Fast+Implementations+of+the+Minimal+Standard+Random+Number+Generator。你可以通过谷歌找到免费的PDF。关于最小标准随机数生成器的原始论文也值得一读。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1497585|Carta的代码在32位机器上提供快速、高质量的随机数。有关更全面的评估，请参阅论文。|1497586|entityMap|0|LINK|mutability|MUTABLE|url|http://portal.acm.org/citation.cfm?id=76372.76379^0|J|20|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

I recommend the academic paper <a href="http://portal.acm.org/citation.cfm?id=76372.76379" rel="nofollow noreferrer">Two Fast Implementations of the Minimal Standard Random Number Generator</a> by David Carta. You can find free PDF through Google. The original paper on the Minimal Standard Random Number Generator is also worth reading.

Carta's code gives fast, high-quality random numbers on 32-bit machines. For a more thorough evaluation, see the paper.

blocks|key|1282859|text|为LFSR113+from+L'écuyer使用the+C+code|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1282860|unsigned+int+lfsr113_Bits+(void)
{
+++static+unsigned+int+z1+=+12345,+z2+=+12345,+z3+=+12345,+z4+=+12345;
+++unsigned+int+b;
+++b++=+((z1+<<+6)+%5E+z1)+>>+13;
+++z1+=+((z1+&+4294967294U)+<<+18)+%5E+b;
+++b++=+((z2+<<+2)+%5E+z2)+>>+27;+
+++z2+=+((z2+&+4294967288U)+<<+2)+%5E+b;
+++b++=+((z3+<<+13)+%5E+z3)+>>+21;
+++z3+=+((z3+&+4294967280U)+<<+7)+%5E+b;
+++b++=+((z4+<<+3)+%5E+z4)+>>+12;
+++z4+=+((z4+&+4294967168U)+<<+13)+%5E+b;
+++return+(z1+%5E+z2+%5E+z3+%5E+z4);
}|code-block|syntax|javascript|1282861|非常高的质量和速度。不要使用rand()做任何事情。它比无用更糟糕。|1282862|entityMap|0|LINK|mutability|MUTABLE|url|http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.43.3639|1|http://www.iro.umontreal.ca/~simardr/rng/lfsr113.c^0|1|L|0|O|A|1|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]|$A|Y|B|Z|1|10]]|C|$]]|$1|D|3|E|5|F|7|11|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|12|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|13|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]]]

Use <a href="http://www.iro.umontreal.ca/~simardr/rng/lfsr113.c" rel="noreferrer">the C code</a> for <a href="http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.43.3639" rel="noreferrer">LFSR113 from L'écuyer</a>:

<pre><code>unsigned int lfsr113_Bits (void)
{
 static unsigned int z1 = 12345, z2 = 12345, z3 = 12345, z4 = 12345;
 unsigned int b;
 b = ((z1 &lt;&lt; 6) ^ z1) &gt;&gt; 13;
 z1 = ((z1 &amp; 4294967294U) &lt;&lt; 18) ^ b;
 b = ((z2 &lt;&lt; 2) ^ z2) &gt;&gt; 27; 
 z2 = ((z2 &amp; 4294967288U) &lt;&lt; 2) ^ b;
 b = ((z3 &lt;&lt; 13) ^ z3) &gt;&gt; 21;
 z3 = ((z3 &amp; 4294967280U) &lt;&lt; 7) ^ b;
 b = ((z4 &lt;&lt; 3) ^ z4) &gt;&gt; 12;
 z4 = ((z4 &amp; 4294967168U) &lt;&lt; 13) ^ b;
 return (z1 ^ z2 ^ z3 ^ z4);
}
</code></pre>

Very high quality and fast. Do NOT use rand() for anything.
It is worse than useless.

blocks|key|1497674|text|更好的是，使用多个线性反馈移位寄存器将它们组合在一起。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1497675|假设sizeof(unsigned)+==+4|offset|length|style|CODE|1497676|unsigned+t1+=+0,+t2+=+0;

unsigned+random()
{
++++unsigned+b;

++++b+=+t1+%5E+(t1+>>+2)+%5E+(t1+>>+6)+%5E+(t1+>>+7);
++++t1+=+(t1+>>+1)+%7C+(~b+<<+31);

++++b+=+(t2+<<+1)+%5E+(t2+<<+2)+%5E+(t1+<<+3)+%5E+(t2+<<+4);
++++t2+=+(t2+<<+1)+%7C+(~b+>>+31);

++++return+t1+%5E+t2;
}|code-block|syntax|javascript|1497677|entityMap^0|0|2|L|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@$D|Q|E|R|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|S|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Better yet, use multiple linear feedback shift registers combine them together.

Assuming that <code>sizeof(unsigned) == 4</code>:

<pre><code>unsigned t1 = 0, t2 = 0;

unsigned random()
{
 unsigned b;

 b = t1 ^ (t1 &gt;&gt; 2) ^ (t1 &gt;&gt; 6) ^ (t1 &gt;&gt; 7);
 t1 = (t1 &gt;&gt; 1) | (~b &lt;&lt; 31);

 b = (t2 &lt;&lt; 1) ^ (t2 &lt;&lt; 2) ^ (t1 &lt;&lt; 3) ^ (t2 &lt;&lt; 4);
 t2 = (t2 &lt;&lt; 1) | (~b &gt;&gt; 31);

 return t1 ^ t2;
}
</code></pre>

blocks|key|1282945|text|有一个名为KISS的简单RNG，它是一个由三个数字组成的随机数生成器。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1282946|/*+Implementation+of+a+32-bit+KISS+generator+which+uses+no+multiply+instructions+*/+

static+unsigned+int+x=123456789,y=234567891,z=345678912,w=456789123,c=0;+

unsigned+int+JKISS32()+{+
++++int+t;+

++++y+%5E=+(y<<5);+y+%5E=+(y>>7);+y+%5E=+(y<<22);+

++++t+=+z%2Bw%2Bc;+z+=+w;+c+=+t+<+0;+w+=+t&2147483647;+

++++x+%2B=+1411392427;+

++++return+x+%2B+y+%2B+w;+
}|code-block|syntax|javascript|1282947|还有一个网站用来测试RNG+http://www.phy.duke.edu/~rgb/General/dieharder.php。|1282948|entityMap|0|LINK|mutability|MUTABLE|url|http://eprint.iacr.org/2011/007.pdf|1|http://www.phy.duke.edu/~rgb/General/dieharder.php^0|5|4|0|0|0|E|1E|1|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@$A|10|B|11|1|12]]|C|$]]|$1|K|3|-4|5|6|7|13|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]]]

There is one simple RNG named <a href="http://eprint.iacr.org/2011/007.pdf" rel="nofollow">KISS</a>, it is one random number generator according to three numbers.

<pre><code>/* Implementation of a 32-bit KISS generator which uses no multiply instructions */ 

static unsigned int x=123456789,y=234567891,z=345678912,w=456789123,c=0; 

unsigned int JKISS32() { 
 int t; 

 y ^= (y&lt;&lt;5); y ^= (y&gt;&gt;7); y ^= (y&lt;&lt;22); 

 t = z+w+c; z = w; c = t &lt; 0; w = t&amp;2147483647; 

 x += 1411392427; 

 return x + y + w; 
}
</code></pre>

Also there is one web site to test RNG <a href="http://www.phy.duke.edu/~rgb/General/dieharder.php" rel="nofollow">http://www.phy.duke.edu/~rgb/General/dieharder.php</a>

I am writing some embedded code in C and need to use the rand() function. Unfortunately, rand() is not supported in the library for the controller. I need a simple implementation that is fast, but more importantly has little space overhead, that produces relatively high-quality random numbers. Does anyone know which algorithm to use or sample code?

EDIT: It's for image processing, so "relatively high quality" means decent cycle length and good uniform properties.

implementation of rand()

图像处理

我正在用C编写一些嵌入式代码，需要使用rand()函数。不幸的是，控制器的库中不支持rand()。我需要一个简单的实现，这是快速的，但更重要的是有很小的空间开销，产生相对高质量的随机数。有人知道要使用哪种算法或示例代码吗？编辑:它是用于图像处理的，所以“相对高质量”意味着良好的周期长度和良好的均匀属性。

问rand()的实现
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