Experimental subsampling API

From NetLogger

Contents 1 Overview 1.1 Defines 1.2 Functions 2 Detailed Description 3 Define Documentation 4 Function Documentation

Overview

Defines

#define 	NL_MAX_SMPL   16
#define 	NL_write_begin(I, L, V, E, F, args...)
#define 	NL_write_end(I, L, V, E, F, args...)

Functions

void 	NL_set_smpl_rate (NL_log_T, double prob_true)
NL_smpl_t 	NL_get_smpl (NL_log_T self)

Detailed Description

This only works with pairs of events in the same static scope (function).

Define Documentation

#define NL_MAX_SMPL   16

Maximum number of things to sample

#define NL_write_begin (I,L,V,E,F,args ...)  	

• Value:

do {                  
  NL_smpl_t smpl = NL_get_smpl(L);                     
  if ((unsigned long)random() <= smpl->rate &&         
  smpl->id_len < NL_MAX_SMPL) {                       
  smpl->id_list[smpl->id_len++] = (I);           
  NL_write((L),(V),(E),(F), ##args);             
  }                                              
} while(0)

• Begin of a sampled begin/end event pair.

#define NL_write_end (I,l,V,E,F,args...)  	

• Value:

do {                    
   int i;                                                  
   NL_smpl_t smpl = NL_get_smpl(L);                        
   for (i=0; i < smpl->id_len; i++ ) {                     
   if ( smpl->id_list[i] == (I) ) {                    
      int j;                                          
      NL_write((L),(V),(E),(F),##args);              
      for (j=i+1; j < smpl->id_len; j++)             
      smpl->id_list[j-1] = smpl->id_list[j];      
      smpl->id_len--;                             
      break;                                      
     }                                             
    }                                              
   } while(0)

End of sampled begin/end event pair.

Function Documentation

NL_smpl_t NL_get_smpl (NL_log_T self)  	

• Get current sampling obj.
• Parameters: self Log object to sample

void NL_set_smpl_rate (NL_log_T, double prob_true) 			

• Set sampling rate for (experimental) sub-sampling API
• Parameters: prob_true Probability 0..1 of a given event being sampled