Which expression is more gas efficient of the following: "n != 0" or "n > 0"?

Question

What is the more gas-efficient expression to check for non-equality? Is it n != 0, or n > 0?

Answer 1

According to the Ethereum Yellow Paper (Appendix G - Fee Schedule), the gas costs for the relevant opcodes are as follows:

• EQ: 3 gas
• ISZERO: 3 gas
• GT: 3 gas

The first expression (n != 0) utilizes both the EQ and the ISZERO opcodes as follows: iszero(eq(x, 0)). While the second expression (n > 0) only utilizes the GT opcode as follows: gt(x, 0).

Therefore, the expression n > 0 is more gas-efficient than n != 0 by 3 gas units.