From c4e3578087ae89f899ff25f94df4b075a552eb00 Mon Sep 17 00:00:00 2001
From: Federico Kunze <31522760+fedekunze@users.noreply.github.com>
Date: Fri, 2 Aug 2019 17:28:50 +0200
Subject: [PATCH] Merge PR #4791: resume simulations at a given height

---
 .../improvements/simulation/_4490-add-init-heigh     |  1 +
 simapp/sim_test.go                                   | 12 +++++++-----
 simapp/utils.go                                      |  2 ++
 x/simulation/simulate.go                             |  8 +++++---
 4 files changed, 15 insertions(+), 8 deletions(-)
 create mode 100644 .pending/improvements/simulation/_4490-add-init-heigh

diff --git a/.pending/improvements/simulation/_4490-add-init-heigh b/.pending/improvements/simulation/_4490-add-init-heigh
new file mode 100644
index 000000000..df6b069c5
--- /dev/null
+++ b/.pending/improvements/simulation/_4490-add-init-heigh
@@ -0,0 +1 @@
+# 4490 add `InitialBlockHeight` flag to resume a simulation from a given block
\ No newline at end of file
diff --git a/simapp/sim_test.go b/simapp/sim_test.go
index a8b7b4965..fd4c98334 100644
--- a/simapp/sim_test.go
+++ b/simapp/sim_test.go
@@ -45,7 +45,8 @@ func init() {
 	flag.StringVar(&exportStatePath, "ExportStatePath", "", "custom file path to save the exported app state JSON")
 	flag.StringVar(&exportStatsPath, "ExportStatsPath", "", "custom file path to save the exported simulation statistics JSON")
 	flag.Int64Var(&seed, "Seed", 42, "simulation random seed")
-	flag.IntVar(&numBlocks, "NumBlocks", 500, "number of blocks")
+	flag.IntVar(&initialBlockHeight, "InitialBlockHeight", 1, "initial block to start the simulation")
+	flag.IntVar(&numBlocks, "NumBlocks", 500, "number of new blocks to simulate from the initial block height")
 	flag.IntVar(&blockSize, "BlockSize", 200, "operations per block")
 	flag.BoolVar(&enabled, "Enabled", false, "enable the simulation")
 	flag.BoolVar(&verbose, "Verbose", false, "verbose log output")
@@ -58,16 +59,17 @@ func init() {
 }
 
 // helper function for populating input for SimulateFromSeed
+// TODO: clean up this function along with the simulation refactor
 func getSimulateFromSeedInput(tb testing.TB, w io.Writer, app *SimApp) (
 	testing.TB, io.Writer, *baseapp.BaseApp, simulation.AppStateFn, int64,
-	simulation.WeightedOperations, sdk.Invariants, int, int, int, string,
+	simulation.WeightedOperations, sdk.Invariants, int, int, int, int, string,
 	bool, bool, bool, bool, bool, map[string]bool) {
 
 	exportParams := exportParamsPath != ""
 
 	return tb, w, app.BaseApp, appStateFn, seed,
 		testAndRunTxs(app), invariants(app),
-		numBlocks, exportParamsHeight, blockSize,
+		initialBlockHeight, numBlocks, exportParamsHeight, blockSize,
 		exportStatsPath, exportParams, commit, lean, onOperation, allInvariants, app.ModuleAccountAddrs()
 }
 
@@ -715,7 +717,7 @@ func TestAppStateDeterminism(t *testing.T) {
 			simulation.SimulateFromSeed(
 				t, os.Stdout, app.BaseApp, appStateFn, seed,
 				testAndRunTxs(app), []sdk.Invariant{},
-				50, 100, 0, "",
+				1, 50, 100, 0, "",
 				false, true, false, false, false, app.ModuleAccountAddrs(),
 			)
 			appHash := app.LastCommitID().Hash
@@ -743,7 +745,7 @@ func BenchmarkInvariants(b *testing.B) {
 	// 2. Run parameterized simulation (w/o invariants)
 	_, params, simErr := simulation.SimulateFromSeed(
 		b, ioutil.Discard, app.BaseApp, appStateFn, seed, testAndRunTxs(app),
-		[]sdk.Invariant{}, numBlocks, exportParamsHeight, blockSize,
+		[]sdk.Invariant{}, initialBlockHeight, numBlocks, exportParamsHeight, blockSize,
 		exportStatsPath, exportParams, commit, lean, onOperation, false, app.ModuleAccountAddrs(),
 	)
 
diff --git a/simapp/utils.go b/simapp/utils.go
index a867615d3..b4f14db26 100644
--- a/simapp/utils.go
+++ b/simapp/utils.go
@@ -33,6 +33,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/x/supply"
 )
 
+// List of available flags for the simulator
 var (
 	genesisFile        string
 	paramsFile         string
@@ -41,6 +42,7 @@ var (
 	exportStatePath    string
 	exportStatsPath    string
 	seed               int64
+	initialBlockHeight int
 	numBlocks          int
 	blockSize          int
 	enabled            bool
diff --git a/x/simulation/simulate.go b/x/simulation/simulate.go
index 59c24a395..ca2b507c1 100644
--- a/x/simulation/simulate.go
+++ b/x/simulation/simulate.go
@@ -47,7 +47,7 @@ func SimulateFromSeed(
 	tb testing.TB, w io.Writer, app *baseapp.BaseApp,
 	appStateFn AppStateFn, seed int64,
 	ops WeightedOperations, invariants sdk.Invariants,
-	numBlocks, exportParamsHeight, blockSize int,
+	initialHeight, numBlocks, exportParamsHeight, blockSize int,
 	exportStatsPath string,
 	exportParams, commit, lean, onOperation, allInvariants bool,
 	blackListedAccs map[string]bool,
@@ -139,10 +139,12 @@ func SimulateFromSeed(
 	}
 
 	// set exported params to the initial state
-	exportedParams = params
+	if exportParams && exportParamsHeight == 0 {
+		exportedParams = params
+	}
 
 	// TODO: split up the contents of this for loop into new functions
-	for height := 1; height <= numBlocks && !stopEarly; height++ {
+	for height := initialHeight; height < numBlocks+initialHeight && !stopEarly; height++ {
 
 		// Log the header time for future lookup
 		pastTimes = append(pastTimes, header.Time)