[閒聊] 野人獻曝...三個亂數產生器--gamma, no …

看板C_and_CPP (C/C++)作者ccbruce (萬年好人)時間18年前 (2006/03/20 00:02)推噓6(6推 0噓 1→)

留言7則, 5人參與討論串1/1

今天買了支新鍵盤，是羅技的得意手。本來呢，是看上了它的輕薄短小，誰知回來才發現－喵的竟然把方向鍵上的home、printscreen等鍵給我乾坤大挪移啦～這樣以後都沒辦法盲打了。真是Orz...。把用了八年的BTC換掉，還真是有點捨不得呢。不管怎樣，這篇文就是這支新嬌客的產品，希望未來可以好好的工作，不要出鎚就是。以下是三支函數，分別可以產生服從gamma、normal及uniform的亂數。不過呢，這是我從幾百年前的參考書裡面照著algorithm作出來的。所以，如果有問題，也請不要鞭我就是。 #define RANDOMIZE \ srand((unsigned int)_getseed()); \ #define RAND ((double)rand()/(double)RAND_MAX) /* This is my random seed, it doesn't use timer() for seeding but uses QueryPerformanceCounter(). */ unsigned int _getseed(void) { LARGE_INTEGER n; if(!QueryPerformanceCounter(&n)) return 0; return (unsigned int)n.QuadPart; } /* This is a function generates random numbers comply gamma distribution */ double _gamma(double alpha, double beta) { double a=pow(2*alpha-1,-0.5),b=alpha-log(4),q=alpha+1/a,t=4.5,d=1+log(t); double u1,u2; double v,y,z,w; redo: RANDOMIZE u1=RAND; u2=RAND; v=a*log(u1/(1-u1)); y=alpha*exp(v); z=pow(u1,2)*u2; w=b+q*v-y; if(w+d-t*z>=0) return y*beta; if(w>=log(z)) return y*beta; goto redo; } /* This is a function generates random numbers comply normal distribution. It implements the POLOR METHOD */11 double _normal(double mean, double variance) { double u1,u2; double v1,v2; double s,z; double stdev; redo: RANDOMIZE u1=RAND; u2=RAND; v1=2*u1-1; v2=2*u2-1; s=pow(v1,2.0)+pow(v2,2.0); if(s>=1) goto redo; z=sqrt(-2*log(s)/s)*v1; stdev=sqrt(variance); return z*stdev+mean; } /* as you see, it's just a uniform generater */ double _uniform(double a, double b) { double u; RANDOMIZE u=RAND; return a+(b-a)*u; } -- -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 218.166.202.151