enabling batch opening and mock tests (#80)

- add mock circuits
- add vanilla and jellyfish plonk gates
- performance tuning

util/src/lib.rs

@@ -0,0 +1,29 @@
+// Copyright (c) 2022 Espresso Systems (espressosys.com)
+// This file is part of the Jellyfish library.
+// You should have received a copy of the MIT License
+// along with the Jellyfish library. If not, see <https://mit-license.org/>.
+
+//! Utilities for parallel code.
+
+/// this function helps with slice iterator creation that optionally use
+/// `par_iter()` when feature flag `parallel` is on.
+///
+/// # Usage
+/// let v = [1, 2, 3, 4, 5];
+/// let sum = parallelizable_slice_iter(&v).sum();
+///
+/// // the above code is a shorthand for (thus equivalent to)
+/// #[cfg(feature = "parallel")]
+/// let sum = v.par_iter().sum();
+/// #[cfg(not(feature = "parallel"))]
+/// let sum = v.iter().sum();
+#[cfg(feature = "parallel")]
+pub fn parallelizable_slice_iter<T: Sync>(data: &[T]) -> rayon::slice::Iter<T> {
+    use rayon::iter::IntoParallelIterator;
+    data.into_par_iter()
+}
+
+#[cfg(not(feature = "parallel"))]
+pub fn parallelizable_slice_iter<T>(data: &[T]) -> core::slice::Iter<T> {
+    data.iter()
+}