From ed093f86f99cd0b158d459328be52585145ff41d Mon Sep 17 00:00:00 2001
From: Rob Walker <rob@solana.com>
Date: Fri, 9 Aug 2019 13:58:46 -0700
Subject: [PATCH] harmonize percentage members (#5459)

* harmonize percentage members

* update tests

* update capitalization when burning fees

* verify capitalization in fee burn

* fixup
---
 core/src/rpc.rs           |  3 ++-
 runtime/src/bank.rs       | 14 ++++++++++++--
 sdk/src/fee_calculator.rs | 19 ++++++++++---------
 3 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/core/src/rpc.rs b/core/src/rpc.rs
index d8e56292e4..914429d1df 100644
--- a/core/src/rpc.rs
+++ b/core/src/rpc.rs
@@ -627,6 +627,7 @@ mod tests {
     use crate::contact_info::ContactInfo;
     use crate::genesis_utils::{create_genesis_block, GenesisBlockInfo};
     use jsonrpc_core::{MetaIoHandler, Output, Response, Value};
+    use solana_sdk::fee_calculator::DEFAULT_BURN_PERCENT;
     use solana_sdk::hash::{hash, Hash};
     use solana_sdk::instruction::InstructionError;
     use solana_sdk::signature::{Keypair, KeypairUtil};
@@ -958,7 +959,7 @@ mod tests {
         let expected = json!({
             "jsonrpc": "2.0",
             "result": [ blockhash.to_string(), {
-                "burnPercent": 50,
+                "burnPercent": DEFAULT_BURN_PERCENT,
                 "lamportsPerSignature": 0,
                 "maxLamportsPerSignature": 0,
                 "minLamportsPerSignature": 0,
diff --git a/runtime/src/bank.rs b/runtime/src/bank.rs
index 0adfdd5ab3..b8879dbdbc 100644
--- a/runtime/src/bank.rs
+++ b/runtime/src/bank.rs
@@ -467,8 +467,11 @@ impl Bank {
         let collector_fees = self.collector_fees.load(Ordering::Relaxed) as u64;
 
         if collector_fees != 0 {
+            let (unburned, burned) = self.fee_calculator.burn(collector_fees);
             // burn a portion of fees
-            self.deposit(&self.collector_id, self.fee_calculator.burn(collector_fees));
+            self.deposit(&self.collector_id, unburned);
+            self.capitalization
+                .fetch_sub(burned as usize, Ordering::Relaxed);
         }
     }
 
@@ -1791,10 +1794,13 @@ mod tests {
         genesis_block.fee_calculator.lamports_per_signature = 4; // something divisible by 2
 
         let expected_fee_paid = genesis_block.fee_calculator.lamports_per_signature;
-        let expected_fee_collected = genesis_block.fee_calculator.burn(expected_fee_paid);
+        let (expected_fee_collected, expected_fee_burned) =
+            genesis_block.fee_calculator.burn(expected_fee_paid);
 
         let mut bank = Bank::new(&genesis_block);
 
+        let capitalization = bank.capitalization();
+
         let key = Keypair::new();
         let tx = system_transaction::transfer(
             &mint_keypair,
@@ -1819,6 +1825,9 @@ mod tests {
             initial_balance + expected_fee_collected
         ); // Leader collects fee after the bank is frozen
 
+        // verify capitalization
+        assert_eq!(capitalization - expected_fee_burned, bank.capitalization());
+
         // Verify that an InstructionError collects fees, too
         let mut bank = Bank::new_from_parent(&Arc::new(bank), &leader, 1);
         let mut tx =
@@ -1929,6 +1938,7 @@ mod tests {
                 + bank
                     .fee_calculator
                     .burn(bank.fee_calculator.lamports_per_signature * 2)
+                    .0
         );
         assert_eq!(results[0], Ok(()));
         assert_eq!(results[1], Ok(()));
diff --git a/sdk/src/fee_calculator.rs b/sdk/src/fee_calculator.rs
index fc0d8635b8..0be45d6277 100644
--- a/sdk/src/fee_calculator.rs
+++ b/sdk/src/fee_calculator.rs
@@ -21,7 +21,7 @@ pub struct FeeCalculator {
     pub min_lamports_per_signature: u64,
     pub max_lamports_per_signature: u64,
 
-    // What portion of collected fees are to be destroyed, percentage-wise
+    // What portion of collected fees are to be destroyed, as a fraction of std::u8::MAX
     pub burn_percent: u8,
 }
 
@@ -29,7 +29,7 @@ pub struct FeeCalculator {
 pub const DEFAULT_TARGET_LAMPORTS_PER_SIGNATURE: u64 = 42;
 pub const DEFAULT_TARGET_SIGNATURES_PER_SLOT: usize =
     710_000 * DEFAULT_TICKS_PER_SLOT as usize / DEFAULT_NUM_TICKS_PER_SECOND as usize;
-pub const DEFAULT_BURN_PERCENT: u8 = 50;
+pub const DEFAULT_BURN_PERCENT: u8 = 127;
 
 impl Default for FeeCalculator {
     fn default() -> Self {
@@ -127,9 +127,10 @@ impl FeeCalculator {
         self.lamports_per_signature * u64::from(message.header.num_required_signatures)
     }
 
-    /// calculate unburned fee from a fee total
-    pub fn burn(&self, fees: u64) -> u64 {
-        fees * u64::from(100 - self.burn_percent) / 100
+    /// calculate unburned fee from a fee total, returns (unburned, burned)
+    pub fn burn(&self, fees: u64) -> (u64, u64) {
+        let unburned = fees * u64::from(std::u8::MAX - self.burn_percent) / u64::from(std::u8::MAX);
+        (unburned, fees - unburned)
     }
 }
 
@@ -143,13 +144,13 @@ mod tests {
     fn test_fee_calculator_burn() {
         let mut fee_calculator = FeeCalculator::default();
 
-        assert_eq!(fee_calculator.burn(2), 1);
+        assert_eq!(fee_calculator.burn(2), (1, 1));
 
         fee_calculator.burn_percent = 0;
 
-        assert_eq!(fee_calculator.burn(2), 2);
-        fee_calculator.burn_percent = 100;
-        assert_eq!(fee_calculator.burn(2), 0);
+        assert_eq!(fee_calculator.burn(2), (2, 0));
+        fee_calculator.burn_percent = std::u8::MAX;
+        assert_eq!(fee_calculator.burn(2), (0, 2));
     }
 
     #[test]