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Merge pull request steemit#2790 from steemit/2785-remove-partial-subs…
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…idization

Remove partial subsidization
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Michael Vandeberg authored Aug 15, 2018
2 parents 1b25c8e + 6d7be50 commit b6c66f4
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65 changes: 12 additions & 53 deletions libraries/chain/steem_evaluator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2351,56 +2351,8 @@ void claim_account_evaluator::do_apply( const claim_account_operation& o )

FC_ASSERT( creator.balance >= o.fee, "Insufficient balance to create account.", ( "creator.balance", creator.balance )( "required", o.fee ) );

FC_TODO( "Remove min() after HF20" );
int64_t creation_fee = std::min( wso.median_props.account_creation_fee.amount.value, STEEM_MAX_ACCOUNT_CREATION_FEE );

FC_ASSERT( o.fee.amount.value <= creation_fee, "Cannot pay more than account creation fee. paid: ${p} fee: ${f}", ("p", o.fee.amount.value)("f", creation_fee) );

int64_t fee_discount = creation_fee - o.fee.amount.value;

if( fee_discount > 0 )
{
// The calculation we want to do is:
//
// current_subsidy = fee_discount / creation_fee
//
// However, this value is between 0 and 1, so we multiply by STEEM_ACCOUNT_SUBSIDY_PRECISION.
// To make sure the numerator doesn't overflow, we want to statically enforce that:
//
// x < numeric_limits<int64_t>::max()
//
// where x, y are the numerator, denominator:
//
// x = fee_discount * STEEM_ACCOUNT_SUBSIDY_PRECISION
// y = creation_fee
//
// In order to round-against-the-user, we actually want the division to round up, i.e.
//
// current_subsidy = ceil(x/y) = floor( (x+y-1)/y )
//
// (The second step is actually an identity which applies to any integers x, y with
// y > 0.) We now need to make sure that the numerator x+y-1 does not overflow.
// We know that:
//
// fee_discount <= STEEM_MAX_ACCOUNT_CREATION_FEE
// y-1 < STEEM_MAX_ACCOUNT_CREATION_FEE
//
// So we know that:
//
// x+y-1 = fee_discount * STEEM_ACCOUNT_SUBSIDY_PRECISION + y-1
// < STEEM_MAX_ACCOUNT_CRAETION_FEE * STEEM_ACCOUNT_SUBSIDY_PRECISION + STEEM_MAX_ACCOUNT_CREATION_FEE
// = STEEM_MAX_ACCOUNT_CREATION_FEE * (STEEM_ACCOUNT_SUBSIDY_PRECISION + 1)
//
// To check that this product does not exceed numeric_limits< int64_t >::max(), we can rearrange
// the inequality, obtaining:
//
// STEEM_MAX_ACCOUNT_CREATION_FEE < numeric_limits<int64_t>::max() / (STEEM_ACCOUNT_SUBSIDY_PRECISION + 1)
//
static_assert( STEEM_MAX_ACCOUNT_CREATION_FEE < (std::numeric_limits< int64_t >::max() / (STEEM_ACCOUNT_SUBSIDY_PRECISION + 1)),
"Following computation will overflow" );

// creation_fee cannot be zero since fee_discount > 0 and validate() enforces fee, fee_discount are non-negative and add to creation_fee
int64_t current_subsidy = ( fee_discount * STEEM_ACCOUNT_SUBSIDY_PRECISION + creation_fee - 1 ) / creation_fee;
if( o.fee.amount == 0 )
{
const auto& gpo = _db.get_dynamic_global_properties();

// This block is a little weird. We want to enforce that only elected witnesses can include the transaction, but
Expand All @@ -2420,7 +2372,7 @@ void claim_account_evaluator::do_apply( const claim_account_operation& o )
/ (STEEM_ACCOUNT_SUBSIDY_BURST_DAYS * 60 * 60 * 24);
uint64_t new_subsidies = current_witness.recent_account_subsidies - std::min( current_witness.recent_account_subsidies, recovered_subsidies );

new_subsidies += current_subsidy;
new_subsidies += STEEM_ACCOUNT_SUBSIDY_PRECISION;

FC_ASSERT( new_subsidies <= wso.single_witness_subsidy_limit, "Witness has claimed too many subsidized accounts recents. Claimed: ${claimed} Limit: ${limit}",
("claimed", new_subsidies)("limit", wso.single_witness_subsidy_limit) );
Expand All @@ -2432,13 +2384,20 @@ void claim_account_evaluator::do_apply( const claim_account_operation& o )
});
}

FC_ASSERT( uint64_t( current_subsidy ) <= gpo.available_account_subsidies, "There are not enough subsidized accounts to claim" );
FC_ASSERT( gpo.available_account_subsidies >= STEEM_ACCOUNT_SUBSIDY_PRECISION, "There are not enough subsidized accounts to claim" );

_db.modify( gpo, [&]( dynamic_global_property_object& gpo )
{
gpo.available_account_subsidies -= current_subsidy;
gpo.available_account_subsidies -= STEEM_ACCOUNT_SUBSIDY_PRECISION;
});
}
else
{
FC_ASSERT( o.fee == wso.median_props.account_creation_fee,
"Cannot pay more than account creation fee. paid: ${p} fee: ${f}",
("p", o.fee.amount.value)
("f", wso.median_props.account_creation_fee) );
}

_db.adjust_balance( _db.get_account( STEEM_NULL_ACCOUNT ), o.fee );

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8 changes: 2 additions & 6 deletions tests/tests/operation_tests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7246,16 +7246,12 @@ BOOST_AUTO_TEST_CASE( claim_account_apply )
BOOST_REQUIRE( db->get_dynamic_global_properties().available_account_subsidies == 1990034 );
BOOST_REQUIRE( db->get< plugins::rc::rc_pool_object >().pool_array[ plugins::rc::resource_new_accounts ] == 1990034 );

BOOST_TEST_MESSAGE( "--- Test success claiming a partial subsidized account" );
BOOST_TEST_MESSAGE( "--- Test failure claiming a partial subsidized account" );
op.fee = ASSET( "2.500 TESTS" );
tx.clear();
tx.operations.push_back( op );
sign( tx, alice_private_key );
db->push_transaction( tx, 0 );
BOOST_REQUIRE( db->get_account( "alice" ).pending_claimed_accounts == 4 );
BOOST_REQUIRE( db->get_account( "alice" ).balance == ASSET( "7.500 TESTS" ) );
BOOST_REQUIRE( db->get_dynamic_global_properties().available_account_subsidies == 1985034 );
BOOST_REQUIRE( db->get< plugins::rc::rc_pool_object >().pool_array[ plugins::rc::resource_new_accounts ] == 1990034 );
BOOST_REQUIRE_THROW( db->push_transaction( tx, 0 ), fc::assert_exception );


BOOST_TEST_MESSAGE( "--- Test failure with no available subsidized accounts" );
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