need to run proof.synthesize in parallel

[fishjar]

Is it possible for the for loops here to run in parallel?

rust-fil-proofs/storage-proofs-porep/src/stacked/circuit/proof.rs

Lines 168 to 177 in ccfea67

	for (i, proof) in proofs.into_iter().enumerate() {
	proof.synthesize(
	&mut cs.namespace(|| format!("challenge_{}", i)),
	public_params.layer_challenges.layers(),
	&comm_d_num,
	&comm_c_num,
	&comm_r_last_num,
	&replica_id_bits,
	)?;
	}

like this:

use rayon::prelude::*;
// ...
        for (i, proof) in proofs.into_par_iter().enumerate() {
            proof.synthesize(
                &mut cs.namespace(|| format!("challenge_{}", i)),
                public_params.layer_challenges.layers(),
                &comm_d_num,
                &comm_c_num,
                &comm_r_last_num,
                &replica_id_bits,
            )?;
        }

or:

use rayon::prelude::*;
// ...
        if CS::is_extensible() {
            let css = proofs
                .into_par_iter()
                .enumerate()
                .map(|(i, proof)| {
                    let mut cs = CS::new();
                    cs.alloc_input(|| "temp synthesize ONE", || Ok(Fr::one())).unwrap();
                    proof.synthesize(
                        &mut cs.namespace(|| format!("challenge_{}", i)),
                        public_params.layer_challenges.layers(),
                        &comm_d_num,
                        &comm_c_num,
                        &comm_r_last_num,
                        &replica_id_bits,
                    ).unwrap();
                    Ok(cs)
                }).collect::<Result<Vec<_>, SynthesisError>>()?;
            for (i, c) in css.into_iter().enumerate() {
                cs.extend(c);
            }
            return Ok(());
        }

        for (i, proof) in proofs.into_iter().enumerate() {
            proof.synthesize(
                &mut cs.namespace(|| format!("challenge_{}", i)),
                public_params.layer_challenges.layers(),
                &comm_d_num,
                &comm_c_num,
                &comm_r_last_num,
                &replica_id_bits,
            )?;
        }