# Rand is slow?

**URL:** <https://www.ruby-forum.com/t/rand-is-slow/130169>\
**Category:** IT\
**Created:** [February 26, 2008, 1:34am UTC](https://www.ruby-forum.com/t/rand-is-slow/130169 "2008-02-26T01:34:07Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![qwerty73](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/q/9d8465/32.png) [@qwerty73](https://www.ruby-forum.com/u/qwerty73)\
**Post date:** [February 26, 2008, 1:34am UTC](https://www.ruby-forum.com/t/rand-is-slow/130169/1 "2008-02-26T01:34:07Z")

</div>

hi , some people could tell me where is the problem:

i’m a newbe of ruby , i will test some alghortim , quicksort and random  
quick sort:

* * *

def quick(a,p,r)  
if p\<r  
q=partition(a,p,r)  
quick(a,p,q-1)  
quick(a,q+1,r)  
end  
end

def partition(a,p,r)  
x=a[r]  
i=p-1  
for j in (p…r-1)

```
if a[j]<=x
  i=i+1
  tmp=a[i]
  a[i]=a[j]
  a[j]=tmp
end

```

end  
t=a[i+1]  
a[i+1]=a[r]  
a[r]=t  
return i+1  
end

def randpart(a,p,r)  
i=rand(a.length)  
tmp=a[r]  
a[r]=a[i]  
a[i]=tmp  
return partition(a,p,r)  
end

def randquick (a,p,r)  
if p\< r  
q=randpart(a,p,r)  
randquick(a,p,q-1)  
randquick(a,q+1,r)  
end  
end

ranvet=[]  
for i in (0…100000)  
ranvet[i]=rand(10000)  
end

start\_time = Time.now  
randquick(ranvet,0,ranvet.length-1)  
total\_time = Time.now - start\_time  
puts “tempo randomquick”  
puts total\_time

ranvet1=[]  
for i in (0…100000)  
ranvet1[i]=rand(10000)  
end

start\_time = Time.now  
quick(ranvet1,0,ranvet.length-1)  
total\_time = Time.now - start\_time  
puts “tempo quick”  
puts total\_time

* * *

for a random chose of partition quicksort will be faster (look at  
introduction to algorithms), why it is not?  
i have make some mistake ?  
or theare are some problem whit rand?  
something in the interpreter?

sorry for my english!  
tanks  
Andrea