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FAQ.md

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Frequently Asked Questions

How to optimize buy / sell CU limit?

Each buy / sell instruction used CUs depend on all the inputs of the instruction:

  • user pubkey, through the associated_user PDA bump seed derivation.
  • mint pubkey, through the bonding_curve, associated_bonding_curve, associated_user PDA bump seed derivation.
  • creator pubkey, through the creator_vault PDA bump seed derivation.
  • for buy, the amount and max_sol_cost inputs are logged as part of instruction execution, so bigger values consume more CUs to log than smaller values.
  • for sell inputs, it's similar.

As an example, for the tx https://solscan.io/tx/5frph8gBFyX7ayBmqntvwpTPwzZ8aF4kdfJAvC52Li2iDnnaRwtmcZP839Cm4YQUFx7GzsUUStCfAy3hAG69ir4u:

    let mint = Pubkey::from_str("Coyj3LtKn1BNSgWc9HsGK5SKoGfEoDaymig4wrN6pump").unwrap();

assert_eq!(
    Pubkey::find_program_address(&[b"bonding-curve", mint.as_ref()], &pump::ID).1,
    255
);

The bonding_curve bump seed for mint Coyj3LtKn1BNSgWc9HsGK5SKoGfEoDaymig4wrN6pump is 255.

While for the tx https://solscan.io/tx/5xozUcJFvRj4ySpE2epSSs95ySxs6cLjs1rV2uaFNkFgsEMBZW53VUa2uc3CVQLVJRYxfQ5JoSzZLiUvAgM4GEJM:

    let mint = Pubkey::from_str("3cLSxG6eXcCD9NSMawkhUcrvVCUC8KHKHMCxx6bhpump").unwrap();

assert_eq!(
    Pubkey::find_program_address(&[b"bonding-curve", mint.as_ref()], &pump::ID).1,
    251
);

The bonding_curve bump seed for mint 3cLSxG6eXcCD9NSMawkhUcrvVCUC8KHKHMCxx6bhpump is 251.

So it is not possible to compute the used CUs without first simulating the buy / sell tx before submission and adding a buffer of 1% to the simulated CUs, because buy instruction executes a bit more code when the bonding curve completes on that buy.

But since tx simulation before buy / sell slows down tx submission and can increase the chances for slippage errors, it is recommended to use a static big enough CU limit like 100_000.