Warm up IndexReader

[Jason.H]

I found my first search on new created IndexReader is slow , but after i made a 
search , it will be much faster 
i'd like to do such "warn up" in the back end of my application rather then 
wait for the user to warm this up because it's a little bit unfriendly design .
    I  know a warmer would do the intial warm up , but i don't know the exact 
way to implement this . i googled this , but i can't find any solution . 
    can anybody do some help here ~ tks advance ! :D