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Merge pull request #1090 from csoler/v0.6-DHT

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tried to improve DHT size estimation code
This commit is contained in:
csoler 2017-11-01 20:33:54 +01:00 committed by GitHub
commit 2d8e9d5bc8
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2 changed files with 45 additions and 50 deletions
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84
libbitdht/src/bitdht/bdpeer.cc
View File

@ -1024,6 +1024,11 @@ int bdSpace::getDhtBucket(const int idx, bdBucket &bucket)
}
uint32_t bdSpace::calcNetworkSize()
{
return calcNetworkSizeWithFlag(~0u) ;
}
uint32_t bdSpace::calcNetworkSizeWithFlag(uint32_t withFlag)
{
std::vector<bdBucket>::iterator it;
@ -1031,76 +1036,66 @@ uint32_t bdSpace::calcNetworkSize()
unsigned long long sum = 0;
unsigned long long no_peers = 0;
uint32_t count = 0;
bool doPrint = false;
bool doAvg = false;
#ifdef BITDHT_DEBUG
std::cerr << "Estimating DHT network size. Flags=" << std::hex << withFlag << std::dec << std::endl;
#endif
int i = 0;
for(it = buckets.begin(); it != buckets.end(); it++, i++)
{
int size = it->entries.size();
int size = 0;
std::list<bdPeer>::iterator lit;
for(lit = it->entries.begin(); lit != it->entries.end(); lit++)
if (withFlag & lit->mPeerFlags)
size++;
int shift = BITDHT_KEY_BITLEN - i;
bool toBig = false;
if (shift > BITDHT_ULLONG_BITS - mFns->bdBucketBitSize() - 1)
{
toBig = true;
shift = BITDHT_ULLONG_BITS - mFns->bdBucketBitSize() - 1;
}
continue ;
unsigned long long no_nets = ((unsigned long long) 1 << shift);
/* use doPrint so it acts as a single switch */
if (size && !doAvg && !doPrint)
{
doAvg = true;
}
if (size && !doPrint)
{
doPrint = true;
}
if (size == 0)
{
/* reset counters - if empty slot - to discount outliers in average */
sum = 0;
no_peers = 0;
count = 0;
}
if (!toBig)
{
no_peers = no_nets * size;
}
if (doPrint && doAvg && !toBig)
{
if (size == mFns->bdNodesPerBucket())
{
/* last average */
doAvg = false;
}
if (no_peers != 0)
if(size < mFns->bdNodesPerBucket() && size > 0)
{
sum += no_peers;
count++;
}
}
#ifdef BITDHT_DEBUG
if(size > 0)
std::cerr << " Bucket " << shift << ": " << size << " / " << mFns->bdNodesPerBucket() << " peers. no_nets=" << no_nets << ". no_peers=" << no_peers << "." << std::endl;
#endif
}
uint32_t NetSize = 0;
if (count != 0)
{
NetSize = sum / count;
}
//std::cerr << "bdSpace::calcNetworkSize() : " << NetSize;
//std::cerr << std::endl;
#ifdef BITDHT_DEBUG
std::cerr << "Estimated net size: " << NetSize << ". Old style estimate: " << calcNetworkSizeWithFlag_old(withFlag) << std::endl;
#endif
return NetSize;
}
uint32_t bdSpace::calcNetworkSizeWithFlag(uint32_t withFlag)
/* (csoler) This is the old method for computing the DHT size estimate. The method is based on averaging the
* estimate given by each bucket: n 2^b where n is the bucket size and b is the number of similar bits
* in this bucket. The idea is that buckets that are not empty nor full give a estimate of the network
* size.
*
* The existing implementation of this method was not using all non empty/full buckets, in order to avoid
* outliers, but this method is also biased, and tends to give a lower value (because it skips the largest buckets)
* especially when the network is very sparse.
*
* The new implementation respects the original estimate without bias, but it still notoriously wrong. Only averaging
* the estimate over a large period of time would produce a reliable value.
*/
uint32_t bdSpace::calcNetworkSizeWithFlag_old(uint32_t withFlag)
{
std::vector<bdBucket>::iterator it;
@ -1190,7 +1185,6 @@ uint32_t bdSpace::calcNetworkSizeWithFlag(uint32_t withFlag)
return NetSize;
}
uint32_t bdSpace::calcSpaceSize()
{
std::vector<bdBucket>::iterator it;

1
libbitdht/src/bitdht/bdpeer.h
View File

@ -184,6 +184,7 @@ int getDhtBucket(const int idx, bdBucket &bucket);
uint32_t calcNetworkSize();
uint32_t calcNetworkSizeWithFlag(uint32_t withFlag);
uint32_t calcNetworkSizeWithFlag_old(uint32_t withFlag);
uint32_t calcSpaceSize();
uint32_t calcSpaceSizeWithFlag(uint32_t withFlag);