6-03 2,532PVs
Power Law分布随机数生成算法：
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#include <stdio.h> #include <time.h> #include <math.h> #include <stdlib.h> #define alpha 1.2 #define min 1 #define max 100 double uniform(double a,double b,long long int *seed) { // printf("seed start:%lldn", *seed); double t; // double seed = (double)s; *seed=2045*(*seed)+1; *seed=*seed-(*seed/1048576)*1048576; // printf("seed:%lldn", *seed); t=(*seed)/1048576.0; t=a+(b-a)*t; return t; } void main() { double x,y; int i,j; float n=(-alpha); long long int s; unsigned int ss; double uniform(double,double,long long int *); //printf("ÇëÊäÈëÁœžö¶ËµãµÄÖµ£šÏÈСºóŽó£©£ºn"); //scanf("%lf,%lf",&min,&max); ss = time(NULL); //printf("ss:%un", ss); srand(ss); s=(long long int)rand(); FILE *fp=fopen("powelaw.txt","w"); for (i=0;i<10;i++) { for (j=0;j<5;j++) { y= uniform(0,1,&s); //printf("%fn",y); x = pow(((pow(max,n+1) - pow(min,n+1))*y + pow(min,n+1)),(1/(n+1))); printf("x=%fn",x); fprintf(fp, "%f n", x); } } fclose(fp); } |
zipf分布随机数生成算法：
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//==================================================== file = genzipf.c ===== //= Program to generate Zipf (power law) distributed random variables = //=========================================================================== //= Notes: 1) Writes to a user specified output file = //= 2) Generates user specified number of values = //= 3) Run times is same as an empirical distribution generator = //= 4) Implements p(i) = C/i^alpha for i = 1 to N where C is the = //= normalization constant (i.e., sum of p(i) = 1). = //=-------------------------------------------------------------------------= //= Example user input: = //= = //= ---------------------------------------- genzipf.c ----- = //= - Program to generate Zipf random variables - = //= -------------------------------------------------------- = //= Output file name ===================================> output.dat = //= Random number seed =================================> 1 = //= Alpha vlaue ========================================> 1.0 = //= N value ============================================> 1000 = //= Number of values to generate =======================> 5 = //= -------------------------------------------------------- = //= - Generating samples to file - = //= -------------------------------------------------------- = //= -------------------------------------------------------- = //= - Done! = //= -------------------------------------------------------- = //=-------------------------------------------------------------------------= //= Example output file ("output.dat" for above): = //= = //= 1 = //= 1 = //= 161 = //= 17 = //= 30 = //=-------------------------------------------------------------------------= //= Build: bcc32 genzipf.c = //=-------------------------------------------------------------------------= //= Execute: genzipf = //=-------------------------------------------------------------------------= //= Author: Kenneth J. Christensen = //= University of South Florida = //= WWW: http://www.csee.usf.edu/~christen = //= Email: christen@csee.usf.edu = //=-------------------------------------------------------------------------= //= History: KJC (11/16/03) - Genesis (from genexp.c) = //=========================================================================== //----- Include files ------------------------------------------------------- #include <assert.h> // Needed for assert() macro #include <stdio.h> // Needed for printf() #include <stdlib.h> // Needed for exit() and ato*() #include <math.h> // Needed for pow() //----- Constants ----------------------------------------------------------- #define FALSE 0 // Boolean false #define TRUE 1 // Boolean true //----- Function prototypes ------------------------------------------------- int zipf(double alpha, int n); // Returns a Zipf random variable double rand_val(int seed); // Jain's RNG //===== Main program ======================================================== void main(void) { FILE *fp; // File pointer to output file char file_name[256]; // Output file name string char temp_string[256]; // Temporary string variable double alpha; // Alpha parameter double n; // N parameter int num_values; // Number of values int zipf_rv; // Zipf random variable int i; // Loop counter // Output banner printf("---------------------------------------- genzipf.c ----- n"); printf("- Program to generate Zipf random variables - n"); printf("-------------------------------------------------------- n"); // Prompt for output filename and then create/open the file printf("Output file name ===================================> "); scanf("%s", file_name); fp = fopen(file_name, "w"); if (fp == NULL) { printf("ERROR in creating output file (%s) n", file_name); exit(1); } // Prompt for random number seed and then use it printf("Random number seed (greater than 0) ================> "); scanf("%s", temp_string); rand_val((int) atoi(temp_string)); // Prompt for alpha value printf("Alpha value ========================================> "); scanf("%s", temp_string); alpha = atof(temp_string); // Prompt for N value printf("N value ============================================> "); scanf("%s", temp_string); n = atoi(temp_string); // Prompt for number of values to generate printf("Number of values to generate =======================> "); scanf("%s", temp_string); num_values = atoi(temp_string); // Output "generating" message printf("-------------------------------------------------------- n"); printf("- Generating samples to file - n"); printf("-------------------------------------------------------- n"); // Generate and output zipf random variables for (i=0; i<num_values; i++) { zipf_rv = zipf(alpha, n); fprintf(fp, "%d n", zipf_rv); } // Output "done" message and close the output file printf("-------------------------------------------------------- n"); printf("- Done! n"); printf("-------------------------------------------------------- n"); fclose(fp); } //=========================================================================== //= Function to generate Zipf (power law) distributed random variables = //= - Input: alpha and N = //= - Output: Returns with Zipf distributed random variable = //=========================================================================== int zipf(double alpha, int n) { static int first = TRUE; // Static first time flag static double c = 0; // Normalization constant double z; // Uniform random number (0 < z < 1) double sum_prob; // Sum of probabilities double zipf_value; // Computed exponential value to be returned int i; // Loop counter // Compute normalization constant on first call only if (first == TRUE) { for (i=1; i<=n; i++) c = c + (1.0 / pow((double) i, alpha)); c = 1.0 / c; first = FALSE; } // Pull a uniform random number (0 < z < 1) do { z = rand_val(0); } while ((z == 0) || (z == 1)); // Map z to the value sum_prob = 0; for (i=1; i<=n; i++) { sum_prob = sum_prob + c / pow((double) i, alpha); if (sum_prob >= z) { zipf_value = i; break; } } // Assert that zipf_value is between 1 and N assert((zipf_value >=1) && (zipf_value <= n)); return(zipf_value); } //========================================================================= //= Multiplicative LCG for generating uniform(0.0, 1.0) random numbers = //= - x_n = 7^5*x_(n-1)mod(2^31 - 1) = //= - With x seeded to 1 the 10000th x value should be 1043618065 = //= - From R. Jain, "The Art of Computer Systems Performance Analysis," = //= John Wiley & Sons, 1991. (Page 443, Figure 26.2) = //========================================================================= double rand_val(int seed) { const long a = 16807; // Multiplier const long m = 2147483647; // Modulus const long q = 127773; // m div a const long r = 2836; // m mod a static long x; // Random int value long x_div_q; // x divided by q long x_mod_q; // x modulo q long x_new; // New x value // Set the seed if argument is non-zero and then return zero if (seed > 0) { x = seed; return(0.0); } // RNG using integer arithmetic x_div_q = x / q; x_mod_q = x % q; x_new = (a * x_mod_q) - (r * x_div_q); if (x_new > 0) x = x_new; else x = x_new + m; // Return a random value between 0.0 and 1.0 return((double) x / m); } |
这两个随机数你用来干什么？？
用来在网络里产生流量用的。
每次来都觉得好洋气呀，哈哈·····
不洋气了，程序员的博客都这样的。嘻嘻