rps-sampler_client.c

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/*
     This file is part of GNUnet.
     Copyright (C)

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     or (at your option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */

#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_statistics_service.h"
#include "rps.h"

#include "rps-sampler_common.h"
#include "gnunet-service-rps_sampler.h"
#include "gnunet-service-rps_sampler_elem.h"

#include <math.h>
#include <inttypes.h>

#include "rps-test_util.h"

#define LOG(kind, ...) GNUNET_log_from(kind, "rps-sampler", __VA_ARGS__)


// multiple 'clients'?

// TODO check for overflows

// TODO align message structs

// hist_size_init, hist_size_max

/***********************************************************************
* WARNING: This section needs to be reviewed regarding the use of
* functions providing (pseudo)randomness!
***********************************************************************/

// TODO care about invalid input of the caller (size 0 or less...)

typedef void
(*SamplerNotifyUpdateCB) (void *cls);

struct SamplerNotifyUpdateCTX {
  SamplerNotifyUpdateCB notify_cb;

  void *cls;

  struct SamplerNotifyUpdateCTX *next;

  struct SamplerNotifyUpdateCTX *prev;
};


typedef void
(*RPS_get_peers_type) (void *cls);


static void
sampler_mod_get_rand_peer(void *cls);


struct RPS_SamplerRequestHandle {
  struct RPS_SamplerRequestHandle *next;
  struct RPS_SamplerRequestHandle *prev;

  uint32_t num_peers;

  uint32_t cur_num_peers;

  struct GNUNET_PeerIdentity *ids;

  struct GetPeerCls *gpc_head;
  struct GetPeerCls *gpc_tail;

  struct RPS_Sampler *sampler;

  RPS_sampler_n_rand_peers_ready_cb callback;

  void *cls;
};


struct RPS_SamplerRequestHandleSingleInfo {
  struct RPS_SamplerRequestHandleSingleInfo *next;
  struct RPS_SamplerRequestHandleSingleInfo *prev;

  struct GNUNET_PeerIdentity *id;

  struct GetPeerCls *gpc_head;
  struct GetPeerCls *gpc_tail;

  struct RPS_Sampler *sampler;

  RPS_sampler_sinlge_info_ready_cb callback;

  void *cls;
};


// * Global sampler variable.
// */
//struct RPS_Sampler *sampler;


static size_t min_size;

static size_t max_size;

//static size_t extra_size;

static uint32_t client_get_index;


struct RPS_Sampler *
RPS_sampler_mod_init(size_t init_size,
                     struct GNUNET_TIME_Relative max_round_interval)
{
  struct RPS_Sampler *sampler;

  /* Initialise context around extended sampler */
  min_size = 10; // TODO make input to _samplers_init()
  max_size = 1000; // TODO make input to _samplers_init()

  sampler = GNUNET_new(struct RPS_Sampler);
  sampler->max_round_interval = max_round_interval;
  sampler->get_peers = sampler_mod_get_rand_peer;
  //sampler->sampler_elements = GNUNET_new_array(init_size, struct GNUNET_PeerIdentity);
  //GNUNET_array_grow (sampler->sampler_elements, sampler->sampler_size, min_size);

  client_get_index = 0;

  //GNUNET_assert (init_size == sampler->sampler_size);

  RPS_sampler_resize(sampler, init_size);

  return sampler;
}


static double
prob_observed_n_peers(uint32_t num_peers_estim,
                      uint32_t num_peers_observed,
                      double deficiency_factor)
{
  uint32_t num_peers = num_peers_estim * (1 / deficiency_factor);
  uint64_t sum = 0;

  for (uint32_t i = 0; i < num_peers; i++)
    {
      uint64_t a = pow(-1, num_peers - i);
      uint64_t b = binom(num_peers, i);
      uint64_t c = pow(i, num_peers_observed);
      sum += a * b * c;
    }

  return sum / (double)pow(num_peers, num_peers_observed);
}


static void
sampler_mod_get_rand_peer(void *cls)
{
  struct GetPeerCls *gpc = cls;
  struct RPS_SamplerElement *s_elem;
  struct GNUNET_TIME_Relative last_request_diff;
  struct RPS_Sampler *sampler;
  double prob_observed_n;
  uint32_t num_observed;

  gpc->get_peer_task = NULL;
  gpc->notify_ctx = NULL;
  GNUNET_assert((NULL != gpc->req_handle) ||
                (NULL != gpc->req_single_info_handle));
  if (NULL != gpc->req_handle)
    sampler = gpc->req_handle->sampler;
  else
    sampler = gpc->req_single_info_handle->sampler;

  LOG(GNUNET_ERROR_TYPE_DEBUG, "Single peer was requested\n");

  /* Cycle the #client_get_index one step further */
  client_get_index = (client_get_index + 1) % sampler->sampler_size;

  s_elem = sampler->sampler_elements[client_get_index];
  *gpc->id = s_elem->peer_id;
  GNUNET_assert(NULL != s_elem);

  if (EMPTY == s_elem->is_empty)
    {
      LOG(GNUNET_ERROR_TYPE_DEBUG,
          "Sampler_mod element empty, rescheduling.\n");
      GNUNET_assert(NULL == gpc->notify_ctx);
      gpc->notify_ctx =
        sampler_notify_on_update(sampler,
                                 &sampler_mod_get_rand_peer,
                                 gpc);
      return;
    }

  /* Check whether we may use this sampler to give it back to the client */
  if (GNUNET_TIME_UNIT_FOREVER_ABS.abs_value_us != s_elem->last_client_request.abs_value_us)
    {
      // TODO remove this condition at least for the client sampler
      last_request_diff =
        GNUNET_TIME_absolute_get_difference(s_elem->last_client_request,
                                            GNUNET_TIME_absolute_get());
      /* We're not going to give it back now if it was
       * already requested by a client this round */
      if (last_request_diff.rel_value_us < sampler->max_round_interval.rel_value_us)
        {
          LOG(GNUNET_ERROR_TYPE_DEBUG,
              "Last client request on this sampler was less than max round interval ago -- scheduling for later\n");
          //inv_last_request_diff =
          //  GNUNET_TIME_absolute_get_difference (last_request_diff,
          //                                       sampler->max_round_interval);
          // add a little delay
          /* Schedule it one round later */
          GNUNET_assert(NULL == gpc->notify_ctx);
          gpc->notify_ctx =
            sampler_notify_on_update(sampler,
                                     &sampler_mod_get_rand_peer,
                                     gpc);
          return;
        }
    }
  if (2 > s_elem->num_peers)
    {
      LOG(GNUNET_ERROR_TYPE_DEBUG,
          "This s_elem saw less than two peers -- scheduling for later\n");
      GNUNET_assert(NULL == gpc->notify_ctx);
      gpc->notify_ctx =
        sampler_notify_on_update(sampler,
                                 &sampler_mod_get_rand_peer,
                                 gpc);
      return;
    }
  /* compute probability */
  /* Currently disabled due to numerical limitations */
  //prob_observed_n = prob_observed_n_peers (sampler->num_peers_estim,
  //                                         s_elem->num_peers,
  //                                         sampler->deficiency_factor);
  //LOG (GNUNET_ERROR_TYPE_DEBUG,
  //    "Computed sample - prob %f, %" PRIu32 " peers, n: %" PRIu32 ", roh: %f\n",
  //    prob_observed_n,
  //    s_elem->num_peers,
  //    sampler->num_peers_estim,
  //    sampler->deficiency_factor);
  //if (prob_observed_n < sampler->desired_probability)
  //{
  //  LOG (GNUNET_ERROR_TYPE_DEBUG,
  //      "Probability of having observed all peers (%f) too small ( < %f).\n",
  //      prob_observed_n,
  //      sampler->desired_probability);
  //  GNUNET_assert (NULL == gpc->notify_ctx);
  //  gpc->notify_ctx =
  //    sampler_notify_on_update (sampler,
  //                              &sampler_mod_get_rand_peer,
  //                              gpc);
  //  return;
  //}
  /* More reasons to wait could be added here */

//  GNUNET_STATISTICS_set (stats,
//                         "# client sampler element input",
//                         s_elem->num_peers,
//                         GNUNET_NO);
//  GNUNET_STATISTICS_set (stats,
//                         "# client sampler element change",
//                         s_elem->num_change,
//                         GNUNET_NO);

  num_observed = s_elem->num_peers;
  RPS_sampler_elem_reinit(s_elem);
  s_elem->last_client_request = GNUNET_TIME_absolute_get();

  if (NULL != gpc->req_handle)
    {
      GNUNET_CONTAINER_DLL_remove(gpc->req_handle->gpc_head,
                                  gpc->req_handle->gpc_tail,
                                  gpc);
    }
  else
    {
      GNUNET_CONTAINER_DLL_remove(gpc->req_single_info_handle->gpc_head,
                                  gpc->req_single_info_handle->gpc_tail,
                                  gpc);
    }
  gpc->cont(gpc->cont_cls, gpc->id, prob_observed_n, num_observed);
  GNUNET_free(gpc);
}


/* end of gnunet-service-rps.c */