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blockchain: always select random outs using triangular distribution

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It was only used by the older blockchain_storage.
We also move the code to the calling blockchain level, to avoid
replicating the code in every DB implementation. This also makes
the get_random_out method obsolete, and we delete it.
This commit is contained in:
moneromooo-monero 2015-08-09 18:07:44 +01:00
parent 9c3715e46a
commit 275894cdef
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GPG Key ID: 686F07454D6CEFC3
6 changed files with 9 additions and 35 deletions
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13
src/blockchain_db/berkeleydb/db_bdb.cpp
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@ -1264,19 +1264,6 @@ uint64_t BlockchainBDB::get_tx_block_height(const crypto::hash& h) const
return (uint64_t)result - 1;
}
//FIXME: make sure the random method used here is appropriate
uint64_t BlockchainBDB::get_random_output(const uint64_t& amount) const
{
LOG_PRINT_L3("BlockchainBDB::" << __func__);
check_open();
uint64_t num_outputs = get_num_outputs(amount);
if (num_outputs == 0)
throw1(OUTPUT_DNE("Attempting to get a random output for an amount, but none exist"));
return crypto::rand<uint64_t>() % num_outputs;
}
uint64_t BlockchainBDB::get_num_outputs(const uint64_t& amount) const
{
LOG_PRINT_L3("BlockchainBDB::" << __func__);

2
src/blockchain_db/berkeleydb/db_bdb.h
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@ -295,8 +295,6 @@ public:
virtual uint64_t get_tx_block_height(const crypto::hash& h) const;
virtual uint64_t get_random_output(const uint64_t& amount) const;
virtual uint64_t get_num_outputs(const uint64_t& amount) const;
virtual output_data_t get_output_key(const uint64_t& amount, const uint64_t& index);

4
src/blockchain_db/blockchain_db.h
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@ -104,7 +104,6 @@
* height get_tx_block_height(hash)
*
* Outputs:
* index get_random_output(amount)
* uint64_t get_num_outputs(amount)
* pub_key get_output_key(amount, index)
* tx_out get_output(tx_hash, index)
@ -463,9 +462,6 @@ public:
// returns height of block that contains transaction with hash <h>
virtual uint64_t get_tx_block_height(const crypto::hash& h) const = 0;
// return global output index of a random output of amount <amount>
virtual uint64_t get_random_output(const uint64_t& amount) const = 0;
// returns the total number of outputs of amount <amount>
virtual uint64_t get_num_outputs(const uint64_t& amount) const = 0;

13
src/blockchain_db/lmdb/db_lmdb.cpp
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@ -1620,19 +1620,6 @@ uint64_t BlockchainLMDB::get_tx_block_height(const crypto::hash& h) const
return *(const uint64_t*)result.mv_data;
}
//FIXME: make sure the random method used here is appropriate
uint64_t BlockchainLMDB::get_random_output(const uint64_t& amount) const
{
LOG_PRINT_L3("BlockchainLMDB::" << __func__);
check_open();
uint64_t num_outputs = get_num_outputs(amount);
if (num_outputs == 0)
throw1(OUTPUT_DNE("Attempting to get a random output for an amount, but none exist"));
return crypto::rand<uint64_t>() % num_outputs;
}
uint64_t BlockchainLMDB::get_num_outputs(const uint64_t& amount) const
{
LOG_PRINT_L3("BlockchainLMDB::" << __func__);

2
src/blockchain_db/lmdb/db_lmdb.h
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@ -157,8 +157,6 @@ public:
virtual uint64_t get_tx_block_height(const crypto::hash& h) const;
virtual uint64_t get_random_output(const uint64_t& amount) const;
virtual uint64_t get_num_outputs(const uint64_t& amount) const;
virtual output_data_t get_output_key(const uint64_t& amount, const uint64_t& index);

10
src/cryptonote_core/blockchain.cpp
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@ -1511,7 +1511,15 @@ bool Blockchain::get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUT
// get a random output index from the DB. If we've already seen it,
// return to the top of the loop and try again, otherwise add it to the
// list of output indices we've seen.
uint64_t i = m_db->get_random_output(amount);
// 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));
uint64_t i = (uint64_t)(frac*num_outs);
// just in case rounding up to 1 occurs after sqrt
if (i == num_outs)
--i;
if (seen_indices.count(i))
{
continue;