Simulation Fault: calculated final stake for delegator X greater than current stake

[alexanderbez]

Summary of Bug

Simulation fault

Version

v0.34.0-rc2

Steps to Reproduce

go test ./cmd/gaia/app -run TestFullGaiaSimulation -SimulationEnabled=true -SimulationNumBlocks=1000 -SimulationVerbose=true -SimulationCommit=true -SimulationSeed=2 -v -timeout 24h

Simulating... block 219/1000, operation 350/353. Panic with err
 calculated final stake for delegator cosmos1men4337plw2uxmtevh2d9m8ggxv5h6ece7y35f greater than current stake: 718214285988.826404694247171120, 718214285988.826404694247171119
goroutine 10 [running]:
runtime/debug.Stack(0x1cb84e0, 0xc0000b6000, 0xc0050d3238)
	/usr/local/go/src/runtime/debug/stack.go:24 +0x9d
github.com/cosmos/cosmos-sdk/x/simulation.SimulateFromSeed.func2(0x1cc2640, 0xc00104a7a0, 0xc00000c1e0, 0xc000112140)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/simulation/simulate.go:127 +0xd5
panic(0x18e74c0, 0xc002a16c10)
	/usr/local/go/src/runtime/panic.go:522 +0x1b5
github.com/cosmos/cosmos-sdk/x/distribution/keeper.Keeper.calculateDelegationRewards(0x1cc2580, 0xc00006bcd0, 0xc00011c620, 0xc00011c620, 0x1cc2580, 0xc00006bd20, 0x1cc25c0, 0xc00006bd30, 0xc0000ef8a0, 0x5, ...)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/distribution/keeper/delegation.go:95 +0x746
github.com/cosmos/cosmos-sdk/x/distribution/keeper.Keeper.withdrawDelegationRewards(0x1cc2580, 0xc00006bcd0, 0xc00011c620, 0xc00011c620, 0x1cc2580, 0xc00006bd20, 0x1cc25c0, 0xc00006bd30, 0xc0000ef8a0, 0x5, ...)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/distribution/keeper/delegation.go:114 +0x301
github.com/cosmos/cosmos-sdk/x/distribution/keeper.Keeper.WithdrawDelegationRewards(0x1cc2580, 0xc00006bcd0, 0xc00011c620, 0xc00011c620, 0x1cc2580, 0xc00006bd20, 0x1cc25c0, 0xc00006bd30, 0xc0000ef8a0, 0x5, ...)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/distribution/keeper/keeper.go:62 +0x20c
github.com/cosmos/cosmos-sdk/x/distribution/keeper.CanWithdrawInvariant.func1.1(0x1c, 0x1cdf400, 0xc0025620e0, 0xc0025620e0)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/distribution/keeper/invariants.go:84 +0x62b
github.com/cosmos/cosmos-sdk/x/staking/keeper.Keeper.IterateValidators(0x1cc2580, 0xc00006bca0, 0x1cc25c0, 0xc00006bcb0, 0xc00011c620, 0x5222280, 0xc00000c3c0, 0x1cdaec0, 0xc0000e7b00, 0xc00011c620, ...)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/staking/keeper/alias_functions.go:21 +0x1fa
github.com/cosmos/cosmos-sdk/x/distribution/keeper.CanWithdrawInvariant.func1(0x1ccec40, 0xc0041b9aa0, 0xc000ff39c0, 0xc, 0x1cc2580, 0xc00006bd20)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/distribution/keeper/invariants.go:78 +0x372
github.com/cosmos/cosmos-sdk/x/distribution/keeper.AllInvariants.func1(0x1ccec40, 0xc0041b9aa0, 0xc000ff39c0, 0xc, 0x18e5440, 0x1ca06f8)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/distribution/keeper/invariants.go:23 +0xe5
github.com/cosmos/cosmos-sdk/x/simulation.PeriodicInvariant.func1(0x1ccec40, 0xc0041b9aa0, 0xc000ff39c0, 0xc, 0x0, 0x0)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/simulation/util.go:72 +0xff
github.com/cosmos/cosmos-sdk/x/simulation.assertAllInvariants(0xc0000b4600, 0xc0001d3000, 0xc0001a64c0, 0x3, 0x3, 0x1a366da, 0x12, 0x1cc2640, 0xc00104a7a0)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/simulation/util.go:20 +0x166
github.com/cosmos/cosmos-sdk/x/simulation.SimulateFromSeed(0x1cdf360, 0xc0000b4600, 0xc0001d3000, 0x1b8d4a0, 0x2, 0xc000104380, 0xe, 0xe, 0xc0001a64c0, 0x3, ...)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/x/simulation/simulate.go:171 +0x1b90
github.com/cosmos/cosmos-sdk/cmd/gaia/app.TestFullGaiaSimulation(0xc0000b4600)
	/Users/aleksbez/go/src/github.com/cosmos/cosmos-sdk/cmd/gaia/app/sim_test.go:361 +0x317
testing.tRunner(0xc0000b4600, 0x1b8d430)
	/usr/local/go/src/testing/testing.go:865 +0xc0
created by testing.(*T).Run
	/usr/local/go/src/testing/testing.go:916 +0x35a

/cc @rigelrozanski @cwgoes

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[alexanderbez]

718214285988.826404694247171120 - 718214285988.826404694247171119 = 1e18
Seems like a rounding error...again :-/

[alexanderbez]

Debugging ref: #3788