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Contents​

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Concepts​

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The Minting Mechanism​

The minting mechanism was designed to:
  • allow for a flexible inflation rate determined by market demand targeting a particular bonded-stake ratio
  • effect a balance between market liquidity and staked supply
In order to best determine the appropriate market rate for inflation rewards, a moving change rate is used. The moving change rate mechanism ensures that if the % bonded is either over or under the goal %-bonded, the inflation rate will adjust to further incentivize or disincentivize being bonded, respectively. Setting the goal %-bonded at less than 100% encourages the network to maintain some non-staked tokens which should help provide some liquidity. It can be broken down in the following way:
  • If the actual percentage of bonded tokens is below the goal %-bonded the inflation rate will increase until a maximum value is reached
  • If the goal % bonded (67% in Cosmos-Hub) is maintained, then the inflation rate will stay constant
  • If the actual percentage of bonded tokens is above the goal %-bonded the inflation rate will decrease until a minimum value is reached

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State​

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Minter​

The minter is a space for holding current inflation information.
  • Minter: 0x00 -> ProtocolBuffer(minter)
proto/cosmos/mint/v1beta1/mint.proto 
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See full example on GitHub

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Params​

The mint module stores its params in state with the prefix of 0x01, it can be updated with governance or the address with authority.
  • Params: mint/params -> legacy_amino(params)
proto/cosmos/mint/v1beta1/mint.proto 
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See full example on GitHub

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Begin-Block​

Minting parameters are recalculated and inflation paid at the beginning of each block.

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Inflation rate calculation​

Inflation rate is calculated using an “inflation calculation function” that’s passed to the NewAppModule function. If no function is passed, then the SDK’s default inflation function will be used (NextInflationRate). In case a custom inflation calculation logic is needed, this can be achieved by defining and passing a function that matches InflationCalculationFn’s signature. 
type InflationCalculationFn func(ctx sdk.Context, minter Minter, params Params, bondedRatio math.LegacyDec) math.LegacyDec

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NextInflationRate​

The target annual inflation rate is recalculated each block. The inflation is also subject to a rate change (positive or negative) depending on the distance from the desired ratio (67%). The maximum rate change possible is defined to be 13% per year, however, the annual inflation is capped as between 7% and 20%. 
NextInflationRate(params Params, bondedRatio math.LegacyDec) (inflation math.LegacyDec) {    inflationRateChangePerYear = (1 - bondedRatio/params.GoalBonded) * params.InflationRateChange    inflationRateChange = inflationRateChangePerYear/blocksPerYr    // increase the new annual inflation for this next block    inflation += inflationRateChange    if inflation > params.InflationMax {        inflation = params.InflationMax    }    if inflation < params.InflationMin {        inflation = params.InflationMin    }    return inflation}

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NextAnnualProvisions​

Calculate the annual provisions based on current total supply and inflation rate. This parameter is calculated once per block. 
NextAnnualProvisions(params Params, totalSupply math.LegacyDec) (provisions math.LegacyDec) {    return Inflation * totalSupply

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BlockProvision​

Calculate the provisions generated for each block based on current annual provisions. The provisions are then minted by the mint module’s ModuleMinterAccount and then transferred to the auth’s FeeCollector ModuleAccount. 
BlockProvision(params Params) sdk.Coin {    provisionAmt = AnnualProvisions/ params.BlocksPerYear    return sdk.NewCoin(params.MintDenom, provisionAmt.Truncate())

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Parameters​

The minting module contains the following parameters:
KeyTypeExample
MintDenomstring”uatom”
InflationRateChangestring (dec)“0.130000000000000000”
InflationMaxstring (dec)“0.200000000000000000”
InflationMinstring (dec)“0.070000000000000000”
GoalBondedstring (dec)“0.670000000000000000”
BlocksPerYearstring (uint64)“6311520”

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Events​

The minting module emits the following events:

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BeginBlocker​

TypeAttribute KeyAttribute Value
mintbonded_ratio{bondedRatio}
mintinflation{inflation}
mintannual_provisions{annualProvisions}
mintamount{amount}

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Client​

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CLI​

A user can query and interact with the mint module using the CLI.

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Query​

The query commands allows users to query mint state. 
simd query mint --help
annual-provisions​
The annual-provisions command allows users to query the current minting annual provisions value 
simd query mint annual-provisions [flags]
Example: 
simd query mint annual-provisions
Example Output: 
22268504368893.612100895088410693
inflation​
The inflation command allows users to query the current minting inflation value 
simd query mint inflation [flags]
Example: 
simd query mint inflation
Example Output: 
0.199200302563256955
params​
The params command allows users to query the current minting parameters 
simd query mint params [flags]
Example: 
blocks_per_year: "4360000"goal_bonded: "0.670000000000000000"inflation_max: "0.200000000000000000"inflation_min: "0.070000000000000000"inflation_rate_change: "0.130000000000000000"mint_denom: stake

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gRPC​

A user can query the mint module using gRPC endpoints.

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AnnualProvisions​

The AnnualProvisions endpoint allows users to query the current minting annual provisions value 
/cosmos.mint.v1beta1.Query/AnnualProvisions
Example: 
grpcurl -plaintext localhost:9090 cosmos.mint.v1beta1.Query/AnnualProvisions
Example Output: 
{  "annualProvisions": "1432452520532626265712995618"}

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Inflation​

The Inflation endpoint allows users to query the current minting inflation value 
/cosmos.mint.v1beta1.Query/Inflation
Example: 
grpcurl -plaintext localhost:9090 cosmos.mint.v1beta1.Query/Inflation
Example Output: 
{  "inflation": "130197115720711261"}

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Params​

The Params endpoint allows users to query the current minting parameters 
/cosmos.mint.v1beta1.Query/Params
Example: 
grpcurl -plaintext localhost:9090 cosmos.mint.v1beta1.Query/Params
Example Output: 
{  "params": {    "mintDenom": "stake",    "inflationRateChange": "130000000000000000",    "inflationMax": "200000000000000000",    "inflationMin": "70000000000000000",    "goalBonded": "670000000000000000",    "blocksPerYear": "6311520"  }}

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REST​

A user can query the mint module using REST endpoints.

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annual-provisions​

/cosmos/mint/v1beta1/annual_provisions
Example: 
curl "localhost:1317/cosmos/mint/v1beta1/annual_provisions"
Example Output: 
{  "annualProvisions": "1432452520532626265712995618"}

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inflation​

/cosmos/mint/v1beta1/inflation
Example: 
curl "localhost:1317/cosmos/mint/v1beta1/inflation"
Example Output: 
{  "inflation": "130197115720711261"}

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params​

/cosmos/mint/v1beta1/params
Example: 
curl "localhost:1317/cosmos/mint/v1beta1/params"
Example Output: 
{  "params": {    "mintDenom": "stake",    "inflationRateChange": "130000000000000000",    "inflationMax": "200000000000000000",    "inflationMin": "70000000000000000",    "goalBonded": "670000000000000000",    "blocksPerYear": "6311520"  }}