195 lines
7 KiB
C++
195 lines
7 KiB
C++
/*
|
|
* Copyright (c) 2015, Cryptonomex, Inc.
|
|
* All rights reserved.
|
|
*
|
|
* This source code is provided for evaluation in private test networks only, until September 8, 2015. After this date, this license expires and
|
|
* the code may not be used, modified or distributed for any purpose. Redistribution and use in source and binary forms, with or without modification,
|
|
* are permitted until September 8, 2015, provided that the following conditions are met:
|
|
*
|
|
* 1. The code and/or derivative works are used only for private test networks consisting of no more than 10 P2P nodes.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
|
|
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
|
|
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
|
|
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
|
|
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
|
|
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
*/
|
|
#pragma once
|
|
|
|
#include <graphene/chain/database.hpp>
|
|
#include <graphene/chain/global_property_object.hpp>
|
|
#include <graphene/chain/witness_object.hpp>
|
|
|
|
namespace graphene { namespace chain {
|
|
|
|
using boost::container::flat_set;
|
|
|
|
witness_id_type database::get_scheduled_witness( uint32_t slot_num )const
|
|
{
|
|
//
|
|
// Each witness gets an arbitration key H(time, witness_id).
|
|
// The witness with the smallest key is selected to go first.
|
|
//
|
|
// As opposed to just using H(time) to determine an index into
|
|
// an array of eligible witnesses, this has the following desirable
|
|
// properties:
|
|
//
|
|
// - Avoid dynamic memory allocation
|
|
// - Decreases (but does not eliminate) the probability that a
|
|
// missed block will change the witness assigned to a future slot
|
|
//
|
|
// The hash function is xorshift* as given in
|
|
// [1] https://en.wikipedia.org/wiki/Xorshift#Xorshift.2A
|
|
//
|
|
|
|
if( slot_num == 0 )
|
|
return GRAPHENE_NULL_WITNESS;
|
|
|
|
const flat_set< witness_id_type >& active_witnesses = get_global_properties().active_witnesses;
|
|
uint32_t n = active_witnesses.size();
|
|
uint64_t min_witness_separation;
|
|
if( GRAPHENE_DEFAULT_MIN_WITNESS_COUNT < 5 && BOOST_UNLIKELY( n < 5 ) )
|
|
{
|
|
// special-case 0 and 1.
|
|
// for 2 give a value which results in witnesses alternating slots
|
|
// when there is no missed block
|
|
// for 3-4 give values which don't lock in a single permutation
|
|
switch( n )
|
|
{
|
|
case 0:
|
|
assert(false);
|
|
case 1:
|
|
return *active_witnesses.begin();
|
|
case 2:
|
|
case 3:
|
|
min_witness_separation = 1;
|
|
break;
|
|
case 4:
|
|
min_witness_separation = 2;
|
|
break;
|
|
}
|
|
}
|
|
else
|
|
min_witness_separation = (n/2)+1;
|
|
|
|
uint64_t current_aslot = get_dynamic_global_properties().current_aslot + slot_num;
|
|
|
|
uint64_t start_of_current_round_aslot = current_aslot - (current_aslot % n);
|
|
uint64_t first_ineligible_aslot = std::min( start_of_current_round_aslot, current_aslot - min_witness_separation );
|
|
//
|
|
// overflow analysis of above subtraction:
|
|
//
|
|
// we always have min_witness_separation <= n, so
|
|
// if current_aslot < min_witness_separation it follows that
|
|
// start_of_current_round_aslot == 0
|
|
//
|
|
// therefore result of above min() is 0 when subtraction overflows
|
|
//
|
|
|
|
first_ineligible_aslot = std::max( first_ineligible_aslot, uint64_t( 1 ) );
|
|
|
|
uint64_t best_k = 0;
|
|
witness_id_type best_wit = GRAPHENE_NULL_WITNESS;
|
|
bool success = false;
|
|
|
|
uint64_t now_hi = get_slot_time( slot_num ).sec_since_epoch();
|
|
now_hi <<= 32;
|
|
|
|
for( const witness_id_type& wit_id : active_witnesses )
|
|
{
|
|
const witness_object& wit = wit_id(*this);
|
|
if( wit.last_aslot >= first_ineligible_aslot )
|
|
continue;
|
|
|
|
/// High performance random generator
|
|
/// http://xorshift.di.unimi.it/
|
|
uint64_t k = now_hi + uint64_t(wit_id)*2685821657736338717ULL;
|
|
k ^= (k >> 12);
|
|
k ^= (k << 25);
|
|
k ^= (k >> 27);
|
|
k *= 2685821657736338717ULL;
|
|
if( k >= best_k )
|
|
{
|
|
best_k = k;
|
|
best_wit = wit_id;
|
|
success = true;
|
|
}
|
|
}
|
|
|
|
// the above loop should choose at least 1 because
|
|
// at most K elements are susceptible to the filter,
|
|
// otherwise we have an inconsistent database (such as
|
|
// wit.last_aslot values that are non-unique or in the future)
|
|
if( !success ) {
|
|
edump((best_k)(slot_num)(first_ineligible_aslot)(current_aslot)(start_of_current_round_aslot)(min_witness_separation)(active_witnesses.size()));
|
|
|
|
for( const witness_id_type& wit_id : active_witnesses )
|
|
{
|
|
const witness_object& wit = wit_id(*this);
|
|
if( wit.last_aslot >= first_ineligible_aslot )
|
|
idump((wit_id)(wit.last_aslot));
|
|
}
|
|
|
|
//
|
|
// TODO: Comment out assert( success ) for production network.
|
|
// This code should never be reached, but it has been observed
|
|
// to rarely happen under conditions we have been unable to
|
|
// reproduce. If this point is reached, we want deterministic,
|
|
// non-crashing behavior. See #274.
|
|
//
|
|
assert( success );
|
|
}
|
|
|
|
return best_wit;
|
|
}
|
|
|
|
fc::time_point_sec database::get_slot_time(uint32_t slot_num)const
|
|
{
|
|
if( slot_num == 0 )
|
|
return fc::time_point_sec();
|
|
|
|
auto interval = block_interval();
|
|
const dynamic_global_property_object& dpo = get_dynamic_global_properties();
|
|
|
|
if( head_block_num() == 0 )
|
|
{
|
|
// n.b. first block is at genesis_time plus one block interval
|
|
fc::time_point_sec genesis_time = dpo.time;
|
|
return genesis_time + slot_num * interval;
|
|
}
|
|
|
|
auto head_block_abs_slot = head_block_time().sec_since_epoch() / interval;
|
|
fc::time_point_sec head_slot_time(head_block_abs_slot * interval);
|
|
|
|
const global_property_object& gpo = get_global_properties();
|
|
|
|
// "slot 0" is head_slot_time
|
|
// "slot 1" is head_slot_time,
|
|
// plus maint interval if head block is a maint block
|
|
// plus block interval if head block is not a maint block
|
|
return head_slot_time
|
|
+ (slot_num +
|
|
(
|
|
(dpo.dynamic_flags & dynamic_global_property_object::maintenance_flag)
|
|
? gpo.parameters.maintenance_skip_slots : 0
|
|
)
|
|
) * interval
|
|
;
|
|
}
|
|
|
|
uint32_t database::get_slot_at_time(fc::time_point_sec when)const
|
|
{
|
|
fc::time_point_sec first_slot_time = get_slot_time( 1 );
|
|
if( when < first_slot_time )
|
|
return 0;
|
|
return (when - first_slot_time).to_seconds() / block_interval() + 1;
|
|
}
|
|
|
|
uint32_t database::witness_participation_rate()const
|
|
{
|
|
const dynamic_global_property_object& dpo = get_dynamic_global_properties();
|
|
return uint64_t(GRAPHENE_100_PERCENT) * dpo.recent_slots_filled.popcount() / 128;
|
|
}
|
|
|
|
} }
|