Fix #492 Have a more personalized difficulty to reach ~5 blocks/member

app/controllers/blockchain.js

@@ -101,7 +101,7 @@ function BlockchainBinding (server) {
     const number = (current && current.number) || 0;
     const issuers = yield server.dal.getUniqueIssuersBetween(number - 1 - conf.blocksRot, number - 1);
     const difficulties = [];
-    const version = current ? current.version : 3;
+    const version = current ? current.version : constants.BLOCK_GENERATED_VERSION;
     for (const issuer of issuers) {
       const member = yield server.dal.getWrittenIdtyByPubkey(issuer);
       const difficulty = yield rules.HELPERS.getTrialLevel(version, member.pubkey, conf, server.dal);

app/lib/dal/fileDAL.js

@@ -215,6 +215,8 @@ function FileDAL(params) {
 
   this.getCountOfPoW = (issuer) => that.blockDAL.getCountOfBlocksIssuedBy(issuer);
 
+  this.getNbIssuedInFrame = (issuer, from) => that.blockDAL.getNbIssuedFrom(issuer, from);
+
   this.getBlocksBetween = (start, end) => Q(this.blockDAL.getBlocks(Math.max(0, start), end));
 
   this.getBlockCurrent = () => co(function*() {

app/lib/dal/sqliteDAL/BlockDAL.js

@@ -108,6 +108,11 @@ function BlockDAL(driver) {
     return res[0].quantity;
   });
 
+  this.getNbIssuedFrom = (issuer, from) => co(function *() {
+    let res = yield that.query('SELECT COUNT(*) as quantity FROM block WHERE issuer = ? and number >= ? and NOT fork', [issuer, from]);
+    return res[0].quantity;
+  });
+
   this.getMoreRecentBlockWithTimeEqualBelow = (maxTime) => co(function *() {
     return (yield that.query('SELECT * FROM block WHERE medianTime <= ? and NOT fork ORDER BY number DESC LIMIT 1', [maxTime]))[0];
   });

app/lib/rules/global_rules.js

@@ -953,7 +953,16 @@ function getTrialLevel (version, issuer, conf, dal) {
         last = { number: current.number };
       }
       const nbBlocksSince = current.number - last.number;
-      let personal_diff = Math.max(powMin, powMin * Math.floor(percentRot * nbPreviousIssuers / (1 + nbBlocksSince)));
+      let personal_diff;
+      if (version == 3) {
+        personal_diff = Math.max(powMin, powMin * Math.floor(percentRot * nbPreviousIssuers / (1 + nbBlocksSince)));
+      } else {
+        const from = current.number - current.issuersFrame + 1;
+        const nbBlocksIssuedInFrame = yield dal.getNbIssuedInFrame(issuer, from);
+        const personal_excess = Math.max(0, (nbBlocksIssuedInFrame / 5) - 1);
+        const personal_handicap = Math.floor(Math.log(1 + personal_excess) / Math.log(1.189));
+        personal_diff = powMin * (1 + Math.floor(percentRot * nbPreviousIssuers / (1 + nbBlocksSince))) + personal_handicap;
+      }
       if (personal_diff + 1 % 16 == 0) {
         personal_diff++;
       }

doc/Protocol.md

@@ -1384,7 +1384,9 @@ This field counts the number of different block issuers between the `IssuersFram
 To be valid, a block fingerprint (whole document + signature) must start with a specific number of zeros + a remaining mark character. Rules is the following, and **relative to a each particular member**:
 
 ```
-PERSONAL_DIFF = MAX [ PoWMin ; PoWMin * FLOOR (percentRot * nbPreviousIssuers / (1 + nbBlocksSince)) ]
+PERSONAL_EXCESS = MAX(0, (nbPersonalBlocksInFrame / 5) - 1)
+PERSONAL_HANDICAP = FLOOR(LN(1 + PERSONAL_EXCESS) / LN(1.189))
+PERSONAL_DIFF = PoWMin * (1 + FLOOR (percentRot * nbPreviousIssuers / (1 + nbBlocksSince))) + PERSONAL_HANDICAP
 
 if (PERSONAL_DIFF + 1) % 16 == 0 then PERSONAL_DIFF = PERSONAL_DIFF + 1
 
@@ -1394,6 +1396,7 @@ NB_ZEROS = (PERSONAL_DIFFICULTY - REMAINDER) / 16
 
 Where:
 
+* `[nbPersonalBlocksInFrame]` is the number of blocks written by the member from block (current `number` - current `issuersFrame` + 1) to current block (included)
 * `[PoWMin]` is the `PoWMin` value of incoming block
 * `[percentRot]` is the protocol parameter
 * `[nbPreviousIssuers] = DifferentIssuersCount(last block of issuer)`