随机生成的64位整数。 [英] generate random 64 bit integer

问题描述

我需要你的帮助，请给我一些advice.from编程珍珠我已经云集了生成随机30位整数的，我们应该这样写

i need your help and please give me some advice.from programming pearls i have studded that to generate random 30 bit integer we should write like this

RAND_MAX*rand()+rand()

但我能做的产生不是30，而是64位的随机整数？我认为非常低效的方法是，如果我将两个30位整数，然后乘以4再次整数位，所以我应该使用什么样的方法？ 我现在使用popcount_1不同的方法，64位，并想在随机整数测试它（我也是测量时间，这每一个需要完成的任务）

but what could i do for generate not 30,but 64 bit random integer?i think that very inefficient method will be if i multiply two 30 bit integer and then multiply again 4 bit integer,so what kind of method should i use? i am using now popcount_1 different method for 64 bit and would like to test it on random integers(i am also measuring time which each one takes to accomplish task)

推荐答案

这可能是一个解决方案，不用乘法：

This could be a solution, without multiplication:

r30 = RAND_MAX*rand()+rand()
s30 = RAND_MAX*rand()+rand()
t4  = rand() & 0xf

res = (r30 << 34) + (s30 << 4) + t4

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