Gas
Gas: Gas is a representation of cost incurred by computational resources per transaction. ParallelChain F assigns a cost to every transaction through gas metering.
Gas costs are divided into two components:
- The compute costs in terms of latency or number of CPU cycles expended by the WASM opcodes required to execute the transaction.
- The storage costs in bytes required to store/update data in the world state.
- The compute costs for precompile functions used by developers to deploy smart contracts on ParallelChain F.
WASM supports a total of 513 opcodes which aid sequential, vectorized, memory, logical operations and exception handling. ParallelChain F ecosystem categorizes these opcodes on basis of their operations. Some opcode families induce non-determinism when executed. These are identified and disallowed in the ParallelChain F ecosystem with the help of a custom middleware.
WASM Opcode Categories
ParallelChain F divides WASM opcodes into three major categories:
-
Opcodes that support mathematical operations on integer and floating point data types, logical operations, exception handling, memory and constants [For example get_local, i32.add, f32.add, i32.load, i32.store etc.].
-
Opcodes that support atomic operations through WASM threads [For example i64.atomic.rmw8.add_u, atomic.notify, etc.].For more information, see here.
-
Opcodes that support Fixed-Width SIMD operations [For example i32x4.add, i16x8.ne, f32x4.add etc.]. For more information, see here.
A subset of these opcodes are known to induce non-determinism when executed.These include floating point operations, fixed width SIMD and atomic operations with WASM threads. For more information about non-determinism in WebAssembly, see here.All non-deterministic opcodes are currently disabled in the ParallelChain F ecosystem. Therefore, transactions consisting of non-deterministic opcodes in their WebAssembly, will generate a Receipt Status Code "Disallowed Opcode", when executed.
Opcode Gas costs
Gas fees for each WASM opcode family are defined in terms of the total latency of the corresponding x86-64 Assembly Instructions, each opcode is translated into. For defining latency of each x86-64 Assembly Instruction, we refer to one specific CPU model from Coffee Lake Refresh, Intel's 9th Generation microprocessor family (family: 06, model: 9E). These costs have been tabulated below.
Constants
| Opcode | Gas Cost |
|---|---|
| I32Const | 0 |
| I64Const | 0 |
Type parameteric operators
| Opcode | Gas Cost |
|---|---|
| Drop | 2 |
| Select | 3 |
Flow control
| Opcode | Gas Cost |
|---|---|
| Nop | 0 |
| Unreachable | 0 |
| Else | 0 |
| Loop | 0 |
| If | 0 |
| Br | 2 |
| BrTable | 2 |
| Call | 2 |
| CallIndirect | 2 |
| Return | 2 |
| BrIf | 3 |
Registers
| Opcode | Gas Cost |
|---|---|
| GlobalGet | 3 |
| GlobalSet | 3 |
| LocalGet | 3 |
| LocalSet | 3 |
Reference Types
| Opcode | Gas Cost |
|---|---|
| RefIsNull | 2 |
| RefFunc | 2 |
| RefNull | 2 |
| ReturnCall | 2 |
| ReturnCallIndirect | 2 |
Exception Handling
| Opcode | Gas Cost |
|---|---|
| CatchAll | 2 |
| Throw | 2 |
| Rethrow | 2 |
| Delegate | 2 |
Bulk Memory Operations
| Opcode | Gas Cost |
|---|---|
| ElemDrop | 1 |
| DataDrop | 1 |
| TableInit | 2 |
| MemoryCopy | 3 |
| MemoryFill | 3 |
| TableCopy | 3 |
| TableFill | 3 |
Memory Operations
| Opcode | Gas Cost |
|---|---|
| I32Load | 3 |
| I64Load | 3 |
| I32Store | 3 |
| I64Store | 3 |
| I32Store8 | 3 |
| I32Store16 | 3 |
| I32Load8S | 3 |
| I32Load8U | 3 |
| I32Load16S | 3 |
| I32Load16U | 3 |
| I64Load8S | 3 |
| I64Load8U | 3 |
| I64Load16S | 3 |
| I64Load16U | 3 |
| I64Load32S | 3 |
| I64Load32U | 3 |
| I64Store8 | 3 |
| I64Store16 | 3 |
| I64Store32 | 3 |
32 and 64-bit Integer Arithmetic Operations
| Opcode | Gas Cost |
|---|---|
| I32Add | 1 |
| I32Sub | 1 |
| I64Add | 1 |
| I64Sub | 1 |
| I64LtS | 1 |
| I64LtU | 1 |
| I64GtS | 1 |
| I64GtU | 1 |
| I64LeS | 1 |
| I64LeU | 1 |
| I64GeS | 1 |
| I64GeU | 1 |
| I32Eqz | 1 |
| I32Eq | 1 |
| I32Ne | 1 |
| I32LtS | 1 |
| I32LtU | 1 |
| I32GtS | 1 |
| I32GtU | 1 |
| I32LeS | 1 |
| I32LeU | 1 |
| I32GeS | 1 |
| I32GeU | 1 |
| I64Eqz | 1 |
| I64Eq | 1 |
| I64Ne | 1 |
| I32And | 1 |
| I32Or | 1 |
| I32Xor | 1 |
| I64And | 1 |
| I64Or | 1 |
| I64Xor | 1 |
| I32Shl | 2 |
| I32ShrU | 2 |
| I32ShrS | 2 |
| I32Rotl | 2 |
| I32Rotr | 2 |
| I64Shl | 2 |
| I64ShrU | 2 |
| I64ShrS | 2 |
| I64Rotl | 2 |
| I64Rotr | 2 |
| I32Mul | 3 |
| I64Mul | 3 |
| I32DivS | 80 |
| I32DivU | 80 |
| I32RemS | 80 |
| I32RemU | 80 |
| I64DivS | 80 |
| I64DivU | 80 |
| I64RemS | 80 |
| I64RemU | 80 |
| I32Clz | 105 |
| I64Clz | 105 |
Type Casting & Truncation Operations
| Opcode | Gas Cost |
|---|---|
| I32WrapI64 | 3 |
| I32Extend8S | 3 |
| I32Extend16S | 3 |
| I64ExtendI32S | 3 |
| I64ExtendI32U | 3 |
| I64Extend8S | 3 |
| I64Extend16S | 3 |
| I64Extend32S | 3 |
Storage Gas Costs
The storage costs defined in ParallelChain F:
| Definition | Operation | Cost |
|---|---|---|
| TX_BASE_GAS | Paid by every transaction. Offsets the cost of reading and then writing 4 specified world state keys (from_account/NTxsFromAccount, from_account/Balance, validator_account/Balance, to_account/Balance). | 44200 |
| BLOCKCHAIN_DATA_BASE | Base cost of writes to blockchain transaction data. | 100 |
| BLOCKCHAIN_DATA_BYTE | Cost of writes to the blockchain transaction data per byte. | 100 |
| WORLD_STATE_READ_WRITE_BASE | Base cost of reads and writes on the World State. | 100 |
| WORLD_STATE_READ_KEY_BYTE | Cost of reading from the World State per key byte. | 150 |
| WORLD_STATE_READ_VALUE_BYTE | Cost of reading from the World State per value byte. | 1 |
| WORLD_STATE_WRITE_KEY_BYTE | Cost of writing into the World State per key byte. | 150 |
| WORLD_STATE_WRITE_VALUE_BYTE | Cost of writing into the World State per value byte. | 150 |
Gas Costs for Precompiles
Gas fees for precompile functions are defined according in terms of the total latency of the emitted x86-64 Assembly Instructions when these functions are executed. For more information on the gas costs for precompiles. Please see "Precompiles Gas Costs"