ArticMine's new block weight algorithm

This curbs runaway growth while still allowing substantial
spikes in block weight

Original specification from ArticMine:

here is the scaling proposal
Define: LongTermBlockWeight
Before fork:
LongTermBlockWeight = BlockWeight
At or after fork:
LongTermBlockWeight = min(BlockWeight, 1.4*LongTermEffectiveMedianBlockWeight)
Note: To avoid possible consensus issues over rounding the LongTermBlockWeight for a given block should be calculated to the nearest byte, and stored as a integer in the block itself. The stored LongTermBlockWeight is then used for future calculations of the LongTermEffectiveMedianBlockWeight and not recalculated each time.
Define:   LongTermEffectiveMedianBlockWeight
LongTermEffectiveMedianBlockWeight = max(300000, MedianOverPrevious100000Blocks(LongTermBlockWeight))
Change Definition of EffectiveMedianBlockWeight
From (current definition)
EffectiveMedianBlockWeight  = max(300000, MedianOverPrevious100Blocks(BlockWeight))
To (proposed definition)
EffectiveMedianBlockWeight  = min(max(300000, MedianOverPrevious100Blocks(BlockWeight)), 50*LongTermEffectiveMedianBlockWeight)
Notes:
1) There are no other changes to the existing penalty formula, median calculation, fees etc.
2) There is the requirement to store the LongTermBlockWeight of a block unencrypted in the block itself. This  is to avoid possible consensus issues over rounding and also to prevent the calculations from becoming unwieldy as we move away from the fork.
3) When the  EffectiveMedianBlockWeight cap is reached it is still possible to mine blocks up to 2x the EffectiveMedianBlockWeight by paying the corresponding penalty.

1 files changed, 16 insertions, 1 deletions

diff --git a/src/blockchain_db/blockchain_db.h b/src/blockchain_db/blockchain_db.h
index 396ae7544..6cd4cf346 100644
--- a/src/blockchain_db/blockchain_db.h
+++ b/src/blockchain_db/blockchain_db.h
@@ -359,12 +359,14 @@ private:
    *
    * @param blk the block to be added
    * @param block_weight the weight of the block (transactions and all)
+   * @param long_term_block_weight the long term block weight of the block (transactions and all)
    * @param cumulative_difficulty the accumulated difficulty after this block
    * @param coins_generated the number of coins generated total after this block
    * @param blk_hash the hash of the block
    */
   virtual void add_block( const block& blk
                 , size_t block_weight
+                , uint64_t long_term_block_weight
                 , const difficulty_type& cumulative_difficulty
                 , const uint64_t& coins_generated
                 , uint64_t num_rct_outs
@@ -376,7 +378,7 @@ private:
    *
    * The subclass implementing this will remove the block data from the top
    * block in the chain.  The data to be removed is that which was added in
-   * BlockchainDB::add_block(const block& blk, size_t block_weight, const difficulty_type& cumulative_difficulty, const uint64_t& coins_generated, const crypto::hash& blk_hash)
+   * BlockchainDB::add_block(const block& blk, size_t block_weight, uint64_t long_term_block_weight, const difficulty_type& cumulative_difficulty, const uint64_t& coins_generated, const crypto::hash& blk_hash)
    *
    * If any of this cannot be done, the subclass should throw the corresponding
    * subclass of DB_EXCEPTION
@@ -790,6 +792,7 @@ public:
    *
    * @param blk the block to be added
    * @param block_weight the size of the block (transactions and all)
+   * @param long_term_block_weight the long term weight of the block (transactions and all)
    * @param cumulative_difficulty the accumulated difficulty after this block
    * @param coins_generated the number of coins generated total after this block
    * @param txs the transactions in the block
@@ -798,6 +801,7 @@ public:
    */
   virtual uint64_t add_block( const block& blk
                             , size_t block_weight
+                            , uint64_t long_term_block_weight
                             , const difficulty_type& cumulative_difficulty
                             , const uint64_t& coins_generated
                             , const std::vector<transaction>& txs
@@ -986,6 +990,17 @@ public:
   virtual uint64_t get_block_already_generated_coins(const uint64_t& height) const = 0;
 
   /**
+   * @brief fetch a block's long term weight
+   *
+   * If the block does not exist, the subclass should throw BLOCK_DNE
+   *
+   * @param height the height requested
+   *
+   * @return the long term weight
+   */
+  virtual uint64_t get_block_long_term_weight(const uint64_t& height) const = 0;
+
+  /**
    * @brief fetch a block's hash
    *
    * The subclass should return hash of the block with the