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Bugfix for special case in substitute_node #404

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Merged
merged 2 commits into from
Nov 30, 2020
Merged

Bugfix for special case in substitute_node #404

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fbea600
special case of substitute (with restrashing).
hriener Nov 30, 2020
a14ea6d
bugfix: avoid recreating the old_node that will be deleted by substit…
hriener Nov 30, 2020
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2 changes: 1 addition & 1 deletion include/mockturtle/networks/aig.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -481,7 +481,7 @@ class aig_network
storage::element_type::node_type _hash_obj;
_hash_obj.children[0] = child0;
_hash_obj.children[1] = child1;
if ( const auto it = _storage->hash.find( _hash_obj ); it != _storage->hash.end() )
if ( const auto it = _storage->hash.find( _hash_obj ); it != _storage->hash.end() && it->second != old_node )
{
return std::make_pair( n, signal( it->second, 0 ) );
}
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33 changes: 33 additions & 0 deletions test/networks/aig.cpp
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Expand Up @@ -811,3 +811,36 @@ TEST_CASE( "invoke take_out_node two times on the same node", "[aig]" )
CHECK( aig.fanout_size( aig.get_node( x1 ) ) == 1u );
CHECK( aig.fanout_size( aig.get_node( x2 ) ) == 1u );
}

TEST_CASE( "substitute node and restrash", "[aig]" )
{
aig_network aig;
auto const x1 = aig.create_pi();
auto const x2 = aig.create_pi();

auto const f1 = aig.create_and( x1, x2 );
auto const f2 = aig.create_and( f1, x2 );
aig.create_po( f2 );

CHECK( aig.fanout_size( aig.get_node( x1 ) ) == 1 );
CHECK( aig.fanout_size( aig.get_node( x2 ) ) == 2 );
CHECK( aig.fanout_size( aig.get_node( f1 ) ) == 1 );
CHECK( aig.fanout_size( aig.get_node( f2 ) ) == 1 );

CHECK( simulate<kitty::static_truth_table<2u>>( aig )[0]._bits == 0x8 );

/* substitute f1 with x1
*
* this is a very interesting test case because replacing f1 with x1
* in f2 makes f2 and f1 equal. a correct implementation will
* create a new entry in the hash, although (x1, x2) is already
* there, because (x1, x2) will be deleted in the next step.
*/
aig.substitute_node( aig.get_node( f1 ), x1 );
CHECK( simulate<kitty::static_truth_table<2u>>( aig )[0]._bits == 0x8 );

CHECK( aig.fanout_size( aig.get_node( x1 ) ) == 1 );
CHECK( aig.fanout_size( aig.get_node( x2 ) ) == 1 );
CHECK( aig.fanout_size( aig.get_node( f1 ) ) == 0 );
CHECK( aig.fanout_size( aig.get_node( f2 ) ) == 1 );
}