Redis Bloom installation and simple implementation

 

Installing an expansion   https://blog.csdn.net/maoyuanming0806/article/details/102798976

Simple to use in the laravel

Lua scripts up

$sh=<<<LUA
    return redis.call('bf.add',KEYS[1],KEYS[2])
LUA;

$result=Redis::eval($sh,2,"java","php");

 

The principle:

 It depends on the bit map, resolved to rely Hash collision Hash value calculated a plurality of times

In java an int variable occupy 8 bytes ( 64 -bit machines) is a 64 binary code composed so on storage 64 bits of information, storing one hundred million calculated on the information of 100 million / 64 * 8 / 1024 / 1024 ≈ 11 MB

 But it is a certain error rate, reduce the error rate is to increase the space and each additional Hash value calculation

 

JAVA simple implementation

 

Package the BF; 

Import Classes in java.util *. ; 

class BloomFilter {
     Private  static  Final  int of DEFAULT_SIZE << 2 = 29; // open space 
    Private  static  Final  int [] = Seeds new new  int [] {. 5,. 7,. 11, 13 is, 31 is , 37, 61,22,2,77,3}; // calculate eight different Hash value 
    Private BitSet to bits = new new BitSet to (of DEFAULT_SIZE); // Bit implementation class 
    Private SimpleHash [] = FUNC new new SimpleHash [Seeds. length]; 

    public BloomFilter () {   // constructors out prior to simulate individual 8
        for ( int I = 0; I <seeds.length; I ++ ) { 
            FUNC [I] = new new SimpleHash (of DEFAULT_SIZE, Seeds [I]); 
        } 
    } 

    public  void the Add (String value) { // add a string to the cloth Long vessel 
        for (SimpleHash F: FUNC) {   // cycle each calculate a hash value 
            bits.set (f.hash (value), to true ); // the corresponding hash bit is set. 1 
        } 
    } 

    public  Boolean the contains ( value string) { // determines whether the character string adding too 
        iF (value == null ) {
             return to false ; 
        } 
        Boolean RET = to true ;
         for (SimpleHash F: FUNC) { // . 8 personal judgment, there is not seen a person does not exist 
            RET RET = && bits.get (f.hash (value)); 
        } 
        return RET ; 
    } 

    // internal class, simpleHash 
    public  static  class SimpleHash {
         Private  int CAP; // bitmap length 
        Private  int SEED; // the hash value calculated 

        public SimpleHash ( int CAP, int SEED) { // constructor assignment
            the this .cap = CAP;
             the this .seed = SEED; 
        } 

        public  int the hash (String value) { // calculated Hash value 
            int Result = 0 ;
             int len = value.length (); // calculate the length of string 
            for ( int I = 0; I <len; I ++ ) { 
                Result = Result + value.charAt SEED * (I); // Switch to ascii code 
            }
             return (CAP -. 1) & Result; // binary aND operation 
        } 
    } 

    public  static  void main(String[] args) {

        BloomFilter bf = new BloomFilter();


        bf.add("java");
        for (int i=0;i<100000000;i++){
            bf.add(i+"n");
        }
        int count=0;
        boolean isOk=false;
        for (int i=0;i<100000000;i++){
                 isOk=bf.contains(UUID.randomUUID().toString()+"nphp");
            if (isOk){
                System.out.println("OK");
                count++;
            }
        }
        System.out.println(bf.contains("java"));
        System.out.println(count);

    }

}

 

 

 

 

 

 

!!!