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22 * @file rps/gnunet-service-rps_sampler.c
23 * @brief sampler implementation
24 * @author Julius Bünger
27 #include "gnunet_util_lib.h"
28 #include "gnunet_statistics_service.h"
31 #include "rps-sampler_common.h"
32 #include "gnunet-service-rps_sampler.h"
33 #include "gnunet-service-rps_sampler_elem.h"
38 #include "rps-test_util.h"
40 #define LOG(kind, ...) GNUNET_log_from(kind,"rps-sampler",__VA_ARGS__)
43 // multiple 'clients'?
45 // TODO check for overflows
47 // TODO align message structs
49 // hist_size_init, hist_size_max
51 /***********************************************************************
52 * WARNING: This section needs to be reviewed regarding the use of
53 * functions providing (pseudo)randomness!
54 ***********************************************************************/
56 // TODO care about invalid input of the caller (size 0 or less...)
59 * @brief Callback called each time a new peer was put into the sampler
61 * @param cls A possibly given closure
64 (*SamplerNotifyUpdateCB) (void *cls);
67 * @brief Context for a callback. Contains callback and closure.
69 * Meant to be an entry in an DLL.
71 struct SamplerNotifyUpdateCTX
74 * @brief The Callback to call on updates
76 SamplerNotifyUpdateCB notify_cb;
79 * @brief The according closure.
84 * @brief Next element in DLL.
86 struct SamplerNotifyUpdateCTX *next;
89 * @brief Previous element in DLL.
91 struct SamplerNotifyUpdateCTX *prev;
96 * Type of function used to differentiate between modified and not modified
100 (*RPS_get_peers_type) (void *cls);
104 * Get one random peer out of the sampled peers.
106 * We might want to reinitialise this sampler after giving the
107 * corrsponding peer to the client.
110 sampler_mod_get_rand_peer (void *cls);
114 * Closure to _get_n_rand_peers_ready_cb()
116 struct RPS_SamplerRequestHandle
121 struct RPS_SamplerRequestHandle *next;
122 struct RPS_SamplerRequestHandle *prev;
125 * Number of peers we are waiting for.
130 * Number of peers we currently have.
132 uint32_t cur_num_peers;
135 * Pointer to the array holding the ids.
137 struct GNUNET_PeerIdentity *ids;
140 * Head and tail for the DLL to store the tasks for single requests
142 struct GetPeerCls *gpc_head;
143 struct GetPeerCls *gpc_tail;
148 struct RPS_Sampler *sampler;
151 * Callback to be called when all ids are available.
153 RPS_sampler_n_rand_peers_ready_cb callback;
156 * Closure given to the callback
162 // * Global sampler variable.
164 //struct RPS_Sampler *sampler;
168 * The minimal size for the extended sampler elements.
170 static size_t min_size;
173 * The maximal size the extended sampler elements should grow to.
175 static size_t max_size;
178 * The size the extended sampler elements currently have.
180 //static size_t extra_size;
183 * Inedex to the sampler element that is the next to be returned
185 static uint32_t client_get_index;
189 * Initialise a modified tuple of sampler elements.
191 * @param init_size the size the sampler is initialised with
192 * @param max_round_interval maximum time a round takes
193 * @return a handle to a sampler that consists of sampler elements.
196 RPS_sampler_mod_init (size_t init_size,
197 struct GNUNET_TIME_Relative max_round_interval)
199 struct RPS_Sampler *sampler;
201 /* Initialise context around extended sampler */
202 min_size = 10; // TODO make input to _samplers_init()
203 max_size = 1000; // TODO make input to _samplers_init()
205 sampler = GNUNET_new (struct RPS_Sampler);
206 sampler->max_round_interval = max_round_interval;
207 sampler->get_peers = sampler_mod_get_rand_peer;
208 //sampler->sampler_elements = GNUNET_new_array(init_size, struct GNUNET_PeerIdentity);
209 //GNUNET_array_grow (sampler->sampler_elements, sampler->sampler_size, min_size);
211 client_get_index = 0;
213 //GNUNET_assert (init_size == sampler->sampler_size);
215 RPS_sampler_resize (sampler, init_size);
222 * @brief Compute the probability that we already observed all peers from a
223 * biased stream of peer ids.
226 * As introduced by Brahms: Factor between the number of unique ids in a
227 * truly random stream and number of unique ids in the gossip stream.
229 * @param num_peers_estim The estimated number of peers in the network
230 * @param num_peers_observed The number of peers the given element has observed
231 * @param deficiency_factor A factor that catches the 'bias' of a random stream
234 * @return The estimated probability
237 prob_observed_n_peers (uint32_t num_peers_estim,
238 uint32_t num_peers_observed,
239 double deficiency_factor)
241 uint32_t num_peers = num_peers_estim * (1/deficiency_factor);
244 for (uint32_t i = 0; i < num_peers; i++)
246 uint64_t a = pow (-1, num_peers-i);
247 uint64_t b = binom (num_peers, i);
248 uint64_t c = pow (i, num_peers_observed);
252 return sum / (double) pow (num_peers, num_peers_observed);
257 * Get one random peer out of the sampled peers.
259 * This reinitialises the queried sampler element.
262 sampler_mod_get_rand_peer (void *cls)
264 struct GetPeerCls *gpc = cls;
265 struct RPS_SamplerElement *s_elem;
266 struct GNUNET_TIME_Relative last_request_diff;
267 struct RPS_Sampler *sampler;
268 double prob_observed_n;
270 gpc->get_peer_task = NULL;
271 gpc->notify_ctx = NULL;
272 sampler = gpc->req_handle->sampler;
274 LOG (GNUNET_ERROR_TYPE_DEBUG, "Single peer was requested\n");
276 /* Cycle the #client_get_index one step further */
277 client_get_index = (client_get_index + 1) % sampler->sampler_size;
279 s_elem = sampler->sampler_elements[client_get_index];
280 *gpc->id = s_elem->peer_id;
281 GNUNET_assert (NULL != s_elem);
283 if (EMPTY == s_elem->is_empty)
285 LOG (GNUNET_ERROR_TYPE_DEBUG,
286 "Sampler_mod element empty, rescheduling.\n");
287 GNUNET_assert (NULL == gpc->notify_ctx);
289 sampler_notify_on_update (sampler,
290 &sampler_mod_get_rand_peer,
295 /* Check whether we may use this sampler to give it back to the client */
296 if (GNUNET_TIME_UNIT_FOREVER_ABS.abs_value_us != s_elem->last_client_request.abs_value_us)
298 // TODO remove this condition at least for the client sampler
300 GNUNET_TIME_absolute_get_difference (s_elem->last_client_request,
301 GNUNET_TIME_absolute_get ());
302 /* We're not going to give it back now if it was
303 * already requested by a client this round */
304 if (last_request_diff.rel_value_us < sampler->max_round_interval.rel_value_us)
306 LOG (GNUNET_ERROR_TYPE_DEBUG,
307 "Last client request on this sampler was less than max round interval ago -- scheduling for later\n");
308 ///* How many time remains untile the next round has started? */
309 //inv_last_request_diff =
310 // GNUNET_TIME_absolute_get_difference (last_request_diff,
311 // sampler->max_round_interval);
312 // add a little delay
313 /* Schedule it one round later */
314 GNUNET_assert (NULL == gpc->notify_ctx);
316 sampler_notify_on_update (sampler,
317 &sampler_mod_get_rand_peer,
322 if (2 > s_elem->num_peers)
324 LOG (GNUNET_ERROR_TYPE_DEBUG,
325 "This s_elem saw less than two peers -- scheduling for later\n");
326 GNUNET_assert (NULL == gpc->notify_ctx);
328 sampler_notify_on_update (sampler,
329 &sampler_mod_get_rand_peer,
333 /* compute probability */
334 prob_observed_n = prob_observed_n_peers (sampler->num_peers_estim,
336 sampler->deficiency_factor);
337 /* check if probability is above desired */
338 if (prob_observed_n >= sampler->desired_probability)
340 LOG (GNUNET_ERROR_TYPE_DEBUG,
341 "Probability of having observed all peers (%d) too small ( < %d).\n",
343 sampler->desired_probability);
344 GNUNET_assert (NULL == gpc->notify_ctx);
346 sampler_notify_on_update (sampler,
347 &sampler_mod_get_rand_peer,
351 /* More reasons to wait could be added here */
353 // GNUNET_STATISTICS_set (stats,
354 // "# client sampler element input",
355 // s_elem->num_peers,
357 // GNUNET_STATISTICS_set (stats,
358 // "# client sampler element change",
359 // s_elem->num_change,
362 RPS_sampler_elem_reinit (s_elem);
363 s_elem->last_client_request = GNUNET_TIME_absolute_get ();
365 GNUNET_CONTAINER_DLL_remove (gpc->req_handle->gpc_head,
366 gpc->req_handle->gpc_tail,
368 gpc->cont (gpc->cont_cls, gpc->id);
373 /* end of gnunet-service-rps.c */