blob: 445229062ab77276f2e17a424f74b72c8d716f58 [file] [log] [blame]
 #include "Stats.h" //----------------------------------------------------------------------------- double chooseK ( int n, int k ) { if(k > (n - k)) k = n - k; double c = 1; for(int i = 0; i < k; i++) { double t = double(n-i) / double(i+1); c *= t; } return c; } double chooseUpToK ( int n, int k ) { double c = 0; for(int i = 1; i <= k; i++) { c += chooseK(n,i); } return c; } //----------------------------------------------------------------------------- // Distribution "score" // TODO - big writeup of what this score means // Basically, we're computing a constant that says "The test distribution is as // uniform, RMS-wise, as a random distribution restricted to (1-X)*100 percent of // the bins. This makes for a nice uniform way to rate a distribution that isn't // dependent on the number of bins or the number of keys // (as long as # keys > # bins * 3 or so, otherwise random fluctuations show up // as distribution weaknesses) double calcScore ( const int * bins, const int bincount, const int keycount ) { double n = bincount; double k = keycount; // compute rms value double r = 0; for(int i = 0; i < bincount; i++) { double b = bins[i]; r += b*b; } r = sqrt(r / n); // compute fill factor double f = (k*k - 1) / (n*r*r - k); // rescale to (0,1) with 0 = good, 1 = bad return 1 - (f / n); } //---------------------------------------------------------------------------- void plot ( double n ) { double n2 = n * 1; if(n2 < 0) n2 = 0; n2 *= 100; if(n2 > 64) n2 = 64; int n3 = (int)n2; if(n3 == 0) printf("."); else { char x = '0' + char(n3); if(x > '9') x = 'X'; printf("%c",x); } } //-----------------------------------------------------------------------------