1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 /* $Id: db_utilities_random.h,v 1.1 2010/08/19 18:09:20 bsouthall Exp $ */ 18 19 #ifndef DB_UTILITIES_RANDOM 20 #define DB_UTILITIES_RANDOM 21 22 #include "db_utilities.h" 23 24 25 26 /***************************************************************** 27 * Lean and mean begins here * 28 *****************************************************************/ 29 /*! 30 * \defgroup LMRandom (LM) Random numbers, random sampling 31 */ 32 /*\{*/ 33 /*! 34 Random Number generator. Initialize with non-zero 35 integer value r. A double between zero and one is 36 returned. 37 \param r seed 38 \return random double 39 */ 40 inline double db_QuickRandomDouble(int &r) 41 { 42 int c; 43 c=r/127773; 44 r=16807*(r-c*127773)-2836*c; 45 if(r<0) r+=2147483647; 46 return((1.0/((double)2147483647))*r); 47 //return (((double)rand())/(double)RAND_MAX); 48 } 49 50 /*! 51 Random Number generator. Initialize with non-zero 52 integer value r. An int between and including 0 and max 53 \param r seed 54 \param max upped limit 55 \return random int 56 */ 57 inline int db_RandomInt(int &r,int max) 58 { 59 double dtemp; 60 int itemp; 61 dtemp=db_QuickRandomDouble(r)*(max+1); 62 itemp=(int) dtemp; 63 if(itemp<=0) return(0); 64 if(itemp>=max) return(max); 65 return(itemp); 66 } 67 68 /*! 69 Generate a random sample indexing into [0..pool_size-1]. 70 \param s sample (out) pre-allocated array of size sample_size 71 \param sample_size size of sample 72 \param pool_size upper limit on item index 73 \param r_seed random number generator seed 74 */ 75 inline void db_RandomSample(int *s,int sample_size,int pool_size,int &r_seed) 76 { 77 int temp,temp2,i,j; 78 79 for(i=0;i<sample_size;i++) 80 { 81 temp=db_RandomInt(r_seed,pool_size-1-i); 82 83 for(j=0;j<i;j++) 84 { 85 if(s[j]<=temp) temp++; 86 else 87 { 88 /*swap*/ 89 temp2=temp; 90 temp=s[j]; 91 s[j]=temp2; 92 } 93 } 94 s[i]=temp; 95 } 96 } 97 /*\}*/ 98 #endif /* DB_UTILITIES_RANDOM */ 99
