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triangular distribution to choose recent outputs more often for mixins

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Javier Smooth 2015-04-05 04:01:00 -07:00
parent 7172bdab60
commit f2e8348be0
1 changed files with 5 additions and 1 deletions
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6
src/cryptonote_core/blockchain_storage.cpp
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@ -30,6 +30,7 @@
#include <algorithm> #include <algorithm>
#include <cstdio> #include <cstdio>
#include <cmath>
#include <boost/archive/binary_oarchive.hpp> #include <boost/archive/binary_oarchive.hpp>
#include <boost/archive/binary_iarchive.hpp> #include <boost/archive/binary_iarchive.hpp>
@ -1081,7 +1082,10 @@ bool blockchain_storage::get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDO
size_t try_count = 0; size_t try_count = 0;
for(uint64_t j = 0; j != req.outs_count && try_count < up_index_limit;) for(uint64_t j = 0; j != req.outs_count && try_count < up_index_limit;)
{ {
size_t i = crypto::rand<size_t>()%up_index_limit; // triangular distribution over [a,b) with a=0, mode c=b=up_index_limit
uint64_t r = crypto::rand<uint64_t>() % ((uint64_t)1 << 53);
double frac = std::sqrt((double)r / ((uint64_t)1 << 53));
size_t i = (size_t)(frac*up_index_limit);
if(used.count(i)) if(used.count(i))
continue; continue;
bool added = add_out_to_get_random_outs(amount_outs, result_outs, amount, i); bool added = add_out_to_get_random_outs(amount_outs, result_outs, amount, i);