HPB Gas Mechanism

Introduction: This document is based on version hpb-1.0.2.3. Since it involves transaction cost when it comes to transfer transaction and smart contract calculation, this article mainly introduces HPB Gas mechanism.

First 1 HPB = 1,000,000,000,000,000,000 Wei i.e. 1^18, 1 Gwei = 1,000,000,000 Wei. Transaction cost = Gas * Gas Price.

HPB measurement unit conversion

Unit	Wei	Kwei	babbage	femtohpb	mwei	lovelace	picohpb
Wei	1	103	103	103	106	106	106
Unit	gwei	shannon	nanohpb	nano	szabo	microhpb	micro
Wei	109	109	109	109	1012	1012	1012
Unit	finney	millihpb	milli	hpb	khpb	grand	mhpb
Wei	1015	1015	1015	1018	1021	1021	1024
Unit	ghpb	thpb	phpb	ehpb	zhpb	yhpb	nhpb
Wei	1027	1030	1033	1036	1039	1042	1045
Unit	dhpb	vhpb	uhpb
Wei	1048	1051	1054

How to collect gas?

Ordinary transaction without smart contract

In HPB main network, transaction cost for ordinary transaction and smart contract transaction is not the same. Generally speaking, in HPB ordinary transaction, the default Gas Units = 10. Gas price varies according to the competition among all HPB nodes and its default value in source code of this version is greater than 1Wei. In reality, the experience value is defined as Gas Price = 18Gwei.

Transaction created by smart contract

Basic cost: Default Gas Units = 53000.

Data cost: The data field in the transaction, 1 per byte

Contract pre-compilation cost: The result is returned based on pre-compiled function. When the pre-compiled function evaluates, different instruction sets collect Gas in different ways. Simple instructions (such as Add, MUL, AND, OR, etc.) collect fixed Gas while complex instructions (such as memory operations MLOAD, SLOAD) collect based on used memory.

Transaction operated by smart contract

Basic cost: Default Gas Units = 10.

Data cost: The data field in the transaction, 1 per byte

Contract pre-compilation cost: The Gas calculation method is different depending on different types of smart contract called. Please refer to HPB source code as follow:

 // Precompiled contract gas prices
        
        EcrecoverGas            uint64 = 3000   // Elliptic curve sender recovery gas price
        Sha256BaseGas           uint64 = 60     // Base price for a SHA256 operation
        Sha256PerWordGas        uint64 = 12     // Per-word price for a SHA256 operation
        Ripemd160BaseGas        uint64 = 600    // Base price for a RIPEMD160 operation
        Ripemd160PerWordGas     uint64 = 120    // Per-word price for a RIPEMD160 operation
        IdentityBaseGas         uint64 = 15     // Base price for a data copy operation
        IdentityPerWordGas      uint64 = 3      // Per-work price for a data copy operation
        ModExpQuadCoeffDiv      uint64 = 20     // Divisor for the quadratic particle of the big int modular exponentiation
        Bn256AddGas             uint64 = 500    // Gas needed for an elliptic curve addition 
        Bn256ScalarMulGas       uint64 = 40000  // Gas needed for an elliptic curve scalar multiplication
        Bn256PairingBaseGas     uint64 = 100000 // Base price for an elliptic curve pairing check
        Bn256PairingPerPointGas uint64 = 80000  // Per-point price for an elliptic curve pairing check


const ( 
        MaximumExtraDataSize  uint64 = 32    // Maximum size extra data may be after Genesis.
        ExpByteGas            uint64 = 10    // Times ceil(log256(exponent)) for the EXP instruction.
        SloadGas              uint64 = 50    // Multiplied by the number of 32-byte words that are copied (round up) for any *COPY operation and added.
        CallValueTransferGas  uint64 = 9000  // Paid for CALL when the value transfer is non-zero.
        CallNewAccountGas     uint64 = 25000 // Paid for CALL when the destination address didn't exist prior.
        TxGas                 uint64 = 10    // Per transaction not creating a contract. NOTE: Not payable on data of calls between transactions. //for testnet
        TxGasContractCreation uint64 = 53000 // Per transaction that creates a contract. NOTE: Not payable on data of calls between transactions.
        TxDataZeroGas         uint64 = 1     // Per byte of data attached to a transaction that equals zero. NOTE: Not payable on data of calls between transactions. //for testnet
        QuadCoeffDiv          uint64 = 512   // Divisor for the quadratic particle of the memory cost equation.
        SstoreSetGas          uint64 = 20000 // Once per SLOAD operation.
        LogDataGas            uint64 = 8     // Per byte in a LOG* operation's data.
        CallStipend           uint64 = 2300  // Free gas given at beginning of call.
        
        Sha3Gas          uint64 = 30    // Once per SHA3 operation.
        Sha3WordGas      uint64 = 6     // Once per word of the SHA3 operation's data.
        SstoreResetGas   uint64 = 5000  // Once per SSTORE operation if the zeroness changes from zero.
        SstoreClearGas   uint64 = 5000  // Once per SSTORE operation if the zeroness doesn't change.
        SstoreRefundGas  uint64 = 15000 // Once per SSTORE operation if the zeroness changes to zero.
        JumpdestGas      uint64 = 1     // Refunded gas, once per SSTORE operation if the zeroness changes to zero.
        EpochDuration    uint64 = 30000 // Duration between proof-of-work epochs. 
        CallGas          uint64 = 40    // Once per CALL operation & message call transaction.
        CreateDataGas    uint64 = 200   // 
        CallCreateDepth  uint64 = 1024  // Maximum depth of call/create stack.
        ExpGas           uint64 = 10    // Once per EXP instruction
        LogGas           uint64 = 375   // Per LOG* operation.
        CopyGas          uint64 = 3     // 
        StackLimit       uint64 = 1024  // Maximum size of VM stack allowed.
        TierStepGas      uint64 = 0     // Once per operation, for a selection of them.
        LogTopicGas      uint64 = 375   // Multiplied by the * of the LOG*, per LOG transaction. e.g. LOG0 incurs 0 * c_txLogTopicGas, LOG4 incurs 4 * c_txLogTopicGas.
        CreateGas        uint64 = 32000 // Once per CREATE operation & contract-creation transaction.
        SuicideRefundGas uint64 = 24000 // Refunded following a suicide operation.
        MemoryGas        uint64 = 3     // Times the address of the (highest referenced byte in memory + 1). NOTE: referencing happens on read, write and in instructions such as RETURN and CALL.
        TxDataNonZeroGas uint64 = 1     // Per byte of data attached to a transaction that is not equal to zero. NOTE: Not payable on data of calls between transactions. //for testnet
        
        MaxCodeSize = 24576 // Maximum bytecode to permit for a contract

Gas price description

In our common ETH wallet, Gas Price will be adjusted at different stages. Generally speaking, the wallet is set for users according to the network conditions. HPB Wallet also helps users set Gas Price by default. The default value of source code in this version is greater than 1Wei and the current experience value is 18Gwei. The same applies to Gas Price of HPB smart contract and the current Gas Price operating in smart contract is 18Gwei.

FAQ

Q1: How to calculate Gas?

A1: Please refer to the calculation method in the above form.

Q2: How much does one transaction cost?

A2: First, it is necessary to determine which kind of transaction it belongs to: ordinary or smart contract. Then calculate according to the Gas in the above form, transaction cost = Gas * Gas Price. For example, Gas in ordinary transaction is a fixed value of 10 without the maximum or minimum one. Please also refer to the table above for smart contract transactions. Each transaction has a minimum Gas requirement. In addition, transaction costs can be set manually. If users wants to make faster transactions, the parameter Gas Price value can be adjusted.

Q3: How much Gas does ordinary transaction cost?

A3: Gas for ordinary transaction is a fixed value of 10.

Q4: How much Gas does smart contract transaction cost? A4: There is no upper limit for Gas in smart contracts.

Q5: Is it necessary to purchase HPB token so as to build on HPB main network when making Dapp?

A5: Yes

Q6: Does Dapp need to lock HPB Token?

A6: The current version does not need to lock, but it requires certain transaction fees in deployment process and in operation.

Q7: Can Dapp be built on the test platform?

A7: Yes, the test chain platform has smart contract functions. Now the latest test chain has not been completely released to the community for use. It will be provided to the community users when it is available and the test chain token will also provided.

Q8: How is the transaction fee allocated?

A8: The transaction fee will be awarded to the outbound nodes that maintains HPB main network.

Q9: How much does smart contract cost at minimum?

A9: For the transaction cost in smart contracts, please refer to the figures in the above form, transaction cost = Gas * Gas Price.

Besides, regarding to the transaction fee, please calculate according to the formula, for example: Take the current Gas Price = 18Gwei as an example, the ordinary contract operation transaction fee = 10 * 18Gwei, the minimum transaction cost for creating smart contract = 53000 * 18Gwei and the minimum transaction cost for executing smart contract = 10 * 18Gwei.