Implement entire Hush block subsidy schedule

We now have our halving schedule implemented until the BR goes to zero.
The data was calculated via two new scripts which are in ./contrib :

$ ./contrib/hush_halvings
1,12500000000,340000
2,312500000,2020000
3,156250000,3700000
4,78125000,5380000
5,39062500,7060000
6,19531250,8740000
7,9765625,10420000
8,4882812,12100000
9,2441406,13780000
10,1220703,15460000
11,610351,17140000
12,305175,18820000
13,152587,20500000
14,76293,22180000
15,38146,23860000
16,19073,25540000
17,9536,27220000
18,4768,28900000
19,2384,30580000
20,1192,32260000
21,596,33940000
22,298,35620000
23,149,37300000
24,74,38980000
25,37,40660000
26,18,42340000
27,9,44020000
28,4,45700000
29,2,47380000
30,1,49060000
31,0,50740000
32,0,52420000
33,0,54100000

$ ./contrib/hush_block_subsidy_per_halving
0,1250000000,1125000000,125000000
1,625000000,562500000,62500000
2,312500000,281250000,31250000
3,156250000,140625000,15625000
4,78125000,70312500,7812500
5,39062500,35156250,3906250
6,19531250,17578125,1953125
7,9765625,8789062,976562
8,4882812,4394531,488281
9,2441406,2197265,244140
10,1220703,1098632,122070
11,610351,549316,61035
12,305175,274658,30517
13,152587,137329,15258
14,76293,68664,7629
15,38146,34332,3814
16,19073,17166,1907
17,9536,8583,953
18,4768,4291,476
19,2384,2145,238
20,1192,1072,119
21,596,536,59
22,298,268,29
23,149,134,14
24,74,67,7
25,37,33,3
26,18,16,1
27,9,8,0
28,4,4,0
29,2,2,0
30,1,1,0
31,0,0,0

These show that the block subsidy for miners goes to 0 at the 31st halving
and that the Founders Reward AKA Dev Tax goes to 0 at the 27th halving. There
is also some current KMD internals code that we inherited that prevents
the FR from being less than 10000, so that code would currently set our FR
to 0 at the 14th halving and lead less HUSH being mined than the planned 21M and
even a bit less than the amount under 21M that normally happens, such as in BTC.
We have some time to deal with the bug, since halving 14 is in about 52 years.

contrib/hush_block_subsidy_per_halving

@@ -0,0 +1,17 @@
+#!/usr/bin/env perl
+# Copyright 2019-2020 The Hush developers
+# Released under the GPLv3
+
+use strict;
+use warnings;
+
+my $x = 12.5 * 100000000;
+my $n = 0;
+while ($n<=31) {
+    #printf "$n,%.16g,%.16g,%.16g\n", $x, $x*0.90, $x*0.1;
+    printf "$n,%d,%d,%d\n", $x, $x*0.90, $x*0.1;
+    $x = $x / 2;
+    $n++;
+    exit if ($x <= 0);
+}
+

contrib/hush_halvings

@@ -0,0 +1,22 @@
+#!/usr/bin/env perl
+# Copyright 2019-2020 The Hush developers
+# Released under the GPLv3
+
+use strict;
+use warnings;
+
+my $x = 340_000;
+my $n = 0;
+my $r = 12_500_000_000;
+while ($n<=32) {
+    printf "%d,%d,%d\n", $n+1, $r, $x + 1680000*$n;
+    # blocktime halving at block 340000
+    if ($n==0) {
+        $r = 3.125 * 100_000_000;
+    } else {
+        $r /= 2;
+    }
+
+    $n++;
+}
+

src/komodo_bitcoind.h

@@ -1241,7 +1241,8 @@ CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams);
 // You specify the BR, and the FR % gets added so 10% of 12.5 is 1.25
 // but to tell the AC params, I need to say "11% of 11.25" is 1.25
 // 11% ie. 1/9th cannot be exactly represented and so the FR has tiny amounts of error unless done manually
-// Do not change this code unless you really know what you are doing.
+// This must be kept in sync with hush_block_subsidy() in komoto_utils.h!
+// Changing these functions are consensus changes!
 // Here Be Dragons! -- Duke Leto
 uint64_t hush_commission(int height)
 {
@@ -1261,56 +1262,28 @@ uint64_t hush_commission(int height)
         INTERVAL = GetArg("-ac_halving2",1680000);  // ~4 years worth of 75s blocks
         fprintf(stderr,"%s: height=%d increasing interval to %d\n", __func__, height, INTERVAL);
     }
-/*
-0,1250000000,1125000000,125000000
-1,312500000,281250000,31250000
-2,156250000,140625000,15625000
-3,78125000,70312500,7812500
-4,39062500,35156250,3906250
-5,19531250,17578125,1953125
-6,9765625,8789062,976562
-7,4882812,4394531,488281
-8,2441406,2197265,244140
-9,1220703,1098632,122070
-10,610351,549316,61035
-11,305175,274658,30517
-12,152587,137329,15258
-13,76293,68664,7629
-14,38146,34332,3814
-15,19073,17166,1907
-16,9536,8583,953
-17,4768,4291,476
-18,2384,2145,238
-19,1192,1072,119
-20,596,536,59
-21,298,268,29
-22,149,134,14
-23,74,67,7
-24,37,33,3
-25,18,16,1
-*/
-
 
     if (height < TRANSITION) {
         commission = 0;
     } else {
         // Just like BTC, BRs in the far future will be slightly less than
         // they should be because exact values are not integers, causing
-        // slightly less coins to be actually mined
+        // slightly less coins to be actually mined and small deviations
+        // to the ideal FR/devtax
         if (height < HALVING1) { // before 1st Halving @ Block 340000 (Nov 2020)
             commission = starting_commission;
         } else if (height < 2020000 ) {
-            commission = 312500000;
+            commission = 31250000;
         } else if (height < 3700000 ) {
-            commission = 156250000;
+            commission = 15625000;
         } else if (height < 5380000 ) {
-            commission = 78125000;
+            commission = 7812500;
         } else if (height < 7060000 ) {
-            commission = 39062500;
+            commission = 3906250;
         } else if (height < 8740000 ) {
-            commission = 19531250;
+            commission = 1953125;
         } else if (height < 10420000) {
-            commission = 9765625;
+            commission = 976562; // 0.5 puposhi deviation, all further BRs have deviation from ideal
         } else if (height < 12100000) {
             commission = 488281;
         } else if (height < 15460000) {
@@ -1350,25 +1323,24 @@ uint64_t hush_commission(int height)
         } else if (height < 44020000) {
             commission = 1;
         } else if (height < 45700000) {
+            // FR goes to zero at Halving 26
             commission = 0;
         } else if (height < 47380000) {
+            // FR still zero at Halving 27
             commission = 0;
         } else if (height < 49060000) {
+            // FR still zero at Halving 28
             commission = 0;
         } else if (height < 50740000) {
+            // FR still zero at Halving 29
             commission = 0;
         } else {
+            // enforce FR=0 for all other heights
+            // This over-rides the -ac_end param via HUSH3 cli args
             commission = 0;
         }
     }
 
-    // Explicitly set the last block reward
-    // BR_END is the block with first zero block reward, which overrides
-    // the -ac_end param on HUSH3
-    if(height >= BR_END) {
-        fprintf(stderr,"%s: HUSH block reward has gone to zero at height %d!!! It was a good run folks\n", __func__, height);
-        commission = 0;
-    }
     if(fDebug)
         fprintf(stderr,"%s: commission=%lu,interval=%d at height %d\n", __func__, commission, INTERVAL, height);
     return commission;

src/komodo_utils.h

@@ -1542,20 +1542,92 @@ uint64_t komodo_max_money()
 }
 
 
-// This implements the Hush Emission Curve
+// This implements the Hush Emission Curve, the miner subsidy part,
+// and must be kept in sync with hush_commision() in komoto_bitcoind.h!
+// Changing these functions are consensus changes!
+// Here Be Dragons! -- Duke Leto
 uint64_t hush_block_subsidy(int height)
 {
-    uint64_t subsidy=0;
+    uint64_t subsidy = 0;
-    //TODO: Cover all halvings until BR=0
+    int32_t HALVING1 = GetArg("-z2zheight",340000),
-    if (nHeight >= 3700000) {
+
-        subsidy = -1;
+    if (height < TRANSITION) {
-    } else if (height >= 2020000) {
+        if(fDebug)
-        subsidy = 140625000;
+            fprintf(stderr,"%s: setting subsidy=0 during transition at height=%d\n",__func__, height);
-    } else if (height >= GetArg("-z2zheight",340000)) {
+        subsidy = 0;
-        subsidy = 281250000;
+    } else {
-    } else if (height >= 128) {
+        // Just like BTC, BRs in the far future will be slightly less than
-        subsidy = 1125000000;
+        // they should be because exact values are not integers, causing
+        // slightly less coins to be actually mined and small deviations
+        // to the ideal FR/devtax
+        if (height < HALVING1) { // before 1st Halving @ Block 340000 (Nov 2020)
+            subsidy = 1125000000;
+        } else if (height < 2020000 ) {
+            subsidy = 281250000;
+        } else if (height < 3700000 ) {
+            subsidy = 140625000;
+        } else if (height < 5380000 ) {
+            subsidy = 70312500;
+        } else if (height < 7060000 ) {
+            subsidy = 35156250;
+        } else if (height < 8740000 ) {
+            subsidy = 17578125;
+        } else if (height < 10420000) {
+            subsidy = 8789062;
+        } else if (height < 12100000) {
+            subsidy = 4394531;
+        } else if (height < 15460000) {
+            subsidy = 2197265;
+        } else if (height < 17140000) {
+            subsidy = 1098632;
+        } else if (height < 18820000) {
+            subsidy = 549316;
+        } else if (height < 23860000) {
+            subsidy = 274658;
+        } else if (height < 23860000) {
+            subsidy = 137329;
+        } else if (height < 25540000) {
+            subsidy = 68664;
+        } else if (height < 27220000) {
+            subsidy = 34332;
+        } else if (height < 27220000) {
+            subsidy = 17166;
+        } else if (height < 28900000) {
+            subsidy = 8583;
+        } else if (height < 30580000) {
+            subsidy = 4291;
+        } else if (height < 32260000) {
+            subsidy = 2145;
+        } else if (height < 33940000) {
+            subsidy = 1072;
+        } else if (height < 35620000) {
+            subsidy = 536;
+        } else if (height < 37300000) {
+            subsidy = 268;
+        } else if (height < 38980000) {
+            subsidy = 134;
+        } else if (height < 40660000) {
+            subsidy = 67;
+        } else if (height < 42340000) {
+            subsidy = 33;
+        } else if (height < 44020000) {
+            subsidy = 16;
+        } else if (height < 45700000) {
+            subsidy = 8;
+        } else if (height < 47380000) {
+            subsidy = 4;
+        } else if (height < 49060000) {
+            subsidy = 2;
+        } else if (height < 50740000) {
+            subsidy = 1;
+        } else {
+            // HUSH Block Reward rounds down to 0 at Block 50740000 which is the 31st halving
+            // because Bitcoin/Zcash/Hush internals don't support 0.5 sat block reward yet ;)
+            subsidy = 0;
+        }
     }
+    if(fDebug)
+        fprintf(stderr,"%s: subsidy=%ul at height=%d\n",__func__,subsidy,height);
     return subsidy;
 }