Cairo 1/2 support from Programs without Gas related functions and builtins

maurotoscano · August 26, 2023, 2:02am

Hello, I’m doing a proof of concept program to support running cairo 1/2 programs without the gas cost related built ins. The starting point is the cairo lang runner.

So far I have removed the call in the cairo lang runner to the create_entry_code() as it’s used here:

github.com

starkware-libs/cairo/blob/98af2f86dfd19a75a8ebe7870e4f69b57fdeb756/crates/cairo-lang-runner/src/lib.rs#L194


      
          
          /// Runs the vm starting from a function in the context of a given starknet state.
          pub fn run_function_with_starknet_context(
              &self,
              func: &Function,
              args: &[Arg],
              available_gas: Option<usize>,
              starknet_state: StarknetState,
          ) -> Result<RunResultStarknet, RunnerError> {
              let initial_gas = self.get_initial_available_gas(func, available_gas)?;
              let (entry_code, builtins) = self.create_entry_code(func, args, initial_gas)?;
              let footer = self.create_code_footer();
              let instructions =
                  chain!(entry_code.iter(), self.casm_program.instructions.iter(), footer.iter());
              let (hints_dict, string_to_hint) = build_hints_dict(instructions.clone());
              let mut hint_processor = CairoHintProcessor {
                  runner: Some(self),
                  starknet_state,
                  string_to_hint,
                  run_resources: RunResources::default(),
              };

And I’m replacing it with one that works like the cairo 0 proof mode (Call rel 4, jmp rel 0 ). This is missing the update of the allocation pointer but in the case of programs without args and builtins it should behave just like the Cairo 0 version.

Since builtins shouldn’t be necessary for simpler programs, I’m also running the virtual machine with a plain layout, but I’m not sure in which cases Cairo 1/2 uses built ins.

Right now this approach seems to be working for programs without recursion, we are trying to find what’s the issue with these programs.

To summarize some specific questions:

How can I know if a program is using a built in ?
Is there something important that I should add from the entry code, when I don’t care about the gas costs?

If someone sees any issue with this approach, do tell.

For reference, these programs seem to be running fine:

Add
Add with function

These are having problems:
https://github.com/lambdaclass/cairo-vm/blob/cairo1_for_prover/cairo1-run/factorial.cairo

ilyalesokhin · October 24, 2023, 8:33am

You can look at create_entry_code() to figure out what builtins are used by a specific function.

github.com

starkware-libs/cairo/blob/98af2f86dfd19a75a8ebe7870e4f69b57fdeb756/crates/cairo-lang-runner/src/lib.rs#L427


      
                  %{ memory[ap + 1] = segments.add() %}
                  ap += 2;
                  [ap + 0] = 0, ap++;
                  // Write Infos segment, n_constructed (0), and n_destructed (0) to the segment.
                  [ap - 2] = [[ap - 3]];
                  [ap - 1] = [[ap - 3] + 1];
                  [ap - 1] = [[ap - 3] + 2];
              }
              ap_offset += 3;
          }
          for ty in func.signature.param_types.iter() {
              let info = self.get_info(ty);
              let ty_size = self.type_sizes[ty];
              let generic_ty = &info.long_id.generic_id;
              if let Some(offset) = builtin_offset.get(generic_ty) {
                  casm_extend! {ctx,
                      [ap + 0] = [fp - offset], ap++;
                  }
              } else if generic_ty == &SystemType::ID {
                  casm_extend! {ctx,
                      %{ memory[ap + 0] = segments.add() %}

The issue with recursive programs is that they need the GasBuiltin.

maurotoscano · October 25, 2023, 1:40am

Thank you Ilya! I’ll check if that solves the problem! This is great news

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Cairo 1/2 support from Programs without Gas related functions and builtins

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