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- /*
- This file is part of GNUnet
- Copyright (C) 2008--2013 GNUnet e.V.
- 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
- */
- /**
- * @file testbed/testbed_api_sd.c
- * @brief functions to calculate standard deviation
- * @author Sree Harsha Totakura <sreeharsha@totakura.in>
- */
- #include "platform.h"
- #include "gnunet_util_lib.h"
- #include "testbed_api_sd.h"
- /**
- * An entry to hold data which will be used to calculate SD
- */
- struct SDEntry
- {
- /**
- * DLL next pointer
- */
- struct SDEntry *next;
- /**
- * DLL prev pointer
- */
- struct SDEntry *prev;
- /**
- * The value to store
- */
- unsigned int amount;
- };
- /**
- * Opaque handle for calculating SD
- */
- struct SDHandle
- {
- /**
- * DLL head for storing entries
- */
- struct SDEntry *head;
- /**
- * DLL tail for storing entries
- */
- struct SDEntry *tail;
- /**
- * Squared sum of data values
- */
- unsigned long long sqsum;
- /**
- * Sum of the data values
- */
- unsigned long sum;
- /**
- * The average of data amounts
- */
- float avg;
- /**
- * The variance
- */
- double vr;
- /**
- * Number of data values; also the length of DLL containing SDEntries
- */
- unsigned int cnt;
- /**
- * max number of entries we can have in the DLL
- */
- unsigned int max_cnt;
- };
- /**
- * Initialize standard deviation calculation handle
- *
- * @param max_cnt the maximum number of readings to keep
- * @return the initialized handle
- */
- struct SDHandle *
- GNUNET_TESTBED_SD_init_ (unsigned int max_cnt)
- {
- struct SDHandle *h;
- GNUNET_assert (1 < max_cnt);
- h = GNUNET_new (struct SDHandle);
- h->max_cnt = max_cnt;
- return h;
- }
- /**
- * Frees the memory allocated to the SD handle
- *
- * @param h the SD handle
- */
- void
- GNUNET_TESTBED_SD_destroy_ (struct SDHandle *h)
- {
- struct SDEntry *entry;
- while (NULL != (entry = h->head))
- {
- GNUNET_CONTAINER_DLL_remove (h->head, h->tail, entry);
- GNUNET_free (entry);
- }
- GNUNET_free (h);
- }
- /**
- * Add a reading to SD
- *
- * @param h the SD handle
- * @param amount the reading value
- */
- void
- GNUNET_TESTBED_SD_add_data_ (struct SDHandle *h, unsigned int amount)
- {
- struct SDEntry *entry;
- double sqavg;
- double sqsum_avg;
- entry = NULL;
- if (h->cnt == h->max_cnt)
- {
- entry = h->head;
- GNUNET_CONTAINER_DLL_remove (h->head, h->tail, entry);
- h->sum -= entry->amount;
- h->sqsum -=
- ((unsigned long) entry->amount) * ((unsigned long) entry->amount);
- h->cnt--;
- }
- GNUNET_assert (h->cnt < h->max_cnt);
- if (NULL == entry)
- entry = GNUNET_new (struct SDEntry);
- entry->amount = amount;
- GNUNET_CONTAINER_DLL_insert_tail (h->head, h->tail, entry);
- h->sum += amount;
- h->cnt++;
- h->avg = ((float) h->sum) / ((float) h->cnt);
- h->sqsum += ((unsigned long) amount) * ((unsigned long) amount);
- sqsum_avg = ((double) h->sqsum) / ((double) h->cnt);
- sqavg = ((double) h->avg) * ((double) h->avg);
- h->vr = sqsum_avg - sqavg;
- }
- /**
- * Calculates the factor by which the given amount differs
- *
- * @param h the SDhandle
- * @param amount the value for which the deviation is returned
- * @param factor the factor by which the given amont differs
- * @return GNUNET_SYSERR if the deviation cannot
- * be calculated; GNUNET_OK if the deviation is returned through factor
- */
- int
- GNUNET_TESTBED_SD_deviation_factor_ (struct SDHandle *h, unsigned int amount,
- int *factor)
- {
- double diff;
- int f;
- int n;
- if (h->cnt < 2)
- return GNUNET_SYSERR;
- if (((float) amount) > h->avg)
- {
- diff = ((float) amount) - h->avg;
- f = 1;
- }
- else
- {
- diff = h->avg - ((float) amount);
- f = -1;
- }
- diff *= diff;
- for (n = 1; n < 4; n++)
- if (diff < (((double) (n * n)) * h->vr))
- break;
- *factor = f * n;
- return GNUNET_OK;
- }
- /* end of testbed_api_sd.c */
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