diff --git a/Cargo.lock b/Cargo.lock
index 043962e..1ecc6f9 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -163,6 +163,7 @@ dependencies = [
  "bincode",
  "coremem",
  "log",
+ "rayon",
  "serde",
 ]
 
diff --git a/crates/applications/buffer_proto5/Cargo.toml b/crates/applications/buffer_proto5/Cargo.toml
index e47a76e..07431f4 100644
--- a/crates/applications/buffer_proto5/Cargo.toml
+++ b/crates/applications/buffer_proto5/Cargo.toml
@@ -8,4 +8,5 @@ edition = "2021"
 bincode = "1.3"  # MIT
 coremem = { path = "../../coremem" }
 log = "0.4"
+rayon = "1.5"  # MIT or Apache 2.0
 serde = "1.0"
diff --git a/crates/applications/buffer_proto5/src/cache.rs b/crates/applications/buffer_proto5/src/cache.rs
index a5f64e1..06a52a0 100644
--- a/crates/applications/buffer_proto5/src/cache.rs
+++ b/crates/applications/buffer_proto5/src/cache.rs
@@ -1,75 +1,215 @@
-use log::trace;
 use serde::{de::DeserializeOwned, Serialize};
+use std::sync::RwLock;
 
 pub struct NoSupplier;
-pub struct DiskCache<K, V, S=NoSupplier> {
+pub type DiskCache<K, V, S=NoSupplier> = DiskCacheImpl<Entries<K, V>, S>;
+pub type SyncDiskCache<K, V, S=NoSupplier> = DiskCacheImpl<SyncEntries<K, V>, S>;
+
+pub struct DiskCacheImpl<E, S=NoSupplier> {
     path: String,
-    entries: Vec<(K, V)>,
+    entries: E,
     supplier: S,
 }
 
-impl<K: DeserializeOwned, V: DeserializeOwned> DiskCache<K, V, NoSupplier> {
+impl<E: EntriesCap> DiskCacheImpl<E, NoSupplier>
+where
+    E::Key: DeserializeOwned,
+    E::Value: DeserializeOwned,
+{
     #[allow(dead_code)]
     pub fn new(path: &str) -> Self {
         Self::new_with_supplier(path, NoSupplier)
     }
 }
 
-impl<K: DeserializeOwned, V: DeserializeOwned, S> DiskCache<K, V, S> {
+impl<E: EntriesCap, S> DiskCacheImpl<E, S>
+where
+    E::Key: DeserializeOwned,
+    E::Value: DeserializeOwned,
+{
     pub fn new_with_supplier(path: &str, supplier: S) -> Self {
         let entries = Self::load_from_disk(path).unwrap_or_default();
         Self {
             path: path.into(),
-            entries,
+            entries: E::from_vec(entries),
             supplier,
         }
     }
-    fn load_from_disk(path: &str) -> Option<Vec<(K, V)>> {
+    fn load_from_disk(path: &str) -> Option<Vec<(E::Key, E::Value)>> {
         let reader = std::io::BufReader::new(std::fs::File::open(path).ok()?);
         bincode::deserialize_from(reader).ok()
     }
 }
 
-impl<K: PartialEq, V, S> DiskCache<K, V, S> {
-    pub fn get(&self, k: &K) -> Option<&V> {
-        self.entries.iter().find(|(comp_k, _v): &&(K, V)| comp_k == k).map(|(_k, v)| v)
-    }
-}
-
-
-impl<K: Serialize, V: Serialize, S> DiskCache<K, V, S> {
-    pub fn insert(&mut self, k: K, v: V) {
-        self.entries.push((k, v));
-        self.flush();
-    }
+impl<E: EntriesCap, S> DiskCacheImpl<E, S>
+where
+    E::Key: Serialize + Clone,
+    E::Value: Serialize + Clone,
+{
     fn flush(&self) {
         let writer = std::io::BufWriter::new(std::fs::File::create(&self.path).unwrap());
-        bincode::serialize_into(writer, &self.entries).unwrap();
+        bincode::serialize_into(writer, &self.entries.to_vec()).unwrap();
     }
 }
 
-impl<K: PartialEq + Serialize, V: Serialize + Clone, S> DiskCache<K, V, S> {
+impl<E: EntriesCap, S> DiskCacheImpl<E, S> 
+where
+    E::Key: PartialEq,
+    E::Value: Clone,
+{
+    #[allow(dead_code)]
+    pub fn get(&self, k: &E::Key) -> Option<E::Value> {
+        self.entries.get(k)
+    }
+}
+
+
+// non-sync insert is mut, while sync is immute
+impl<K: Serialize + Clone + PartialEq, V: Serialize + Clone, S> DiskCache<K, V, S> {
+    #[allow(dead_code)]
+    /// insert this k/v ONLY IF NOT PRESENT
+    pub fn insert(&mut self, k: K, v: V) {
+        self.entries.insert(k, v);
+        self.flush();
+    }
+}
+impl<K: Serialize + Clone + PartialEq, V: Serialize + Clone, S> SyncDiskCache<K, V, S> {
+    #[allow(dead_code)]
+    /// insert this k/v ONLY IF NOT PRESENT
+    pub fn insert(&self, k: K, v: V) {
+        self.entries.insert(k, v);
+        self.flush();
+    }
+}
+
+// non-sync insert is mut, while sync is immute
+impl<K: Serialize + Clone + PartialEq, V: Serialize + Clone, S> DiskCache<K, V, S> {
     #[allow(dead_code)]
     pub fn get_or_insert_with<F: FnOnce() -> V>(&mut self, k: K, f: F) -> V {
-        if let Some(v) = self.get(&k) {
-            return v.clone();
-        }
-
-        let v = f();
-        self.insert(k, v.clone());
-        v
+        self.entries.get_or_insert_with(k, |_| f())
+    }
+}
+impl<K: Serialize + Clone + PartialEq, V: Serialize + Clone, S> SyncDiskCache<K, V, S> {
+    #[allow(dead_code)]
+    pub fn get_or_insert_with<F: FnOnce() -> V>(&self, k: K, f: F) -> V {
+        self.entries.get_or_insert_with(k, |_| f())
     }
 }
 
-impl<K: PartialEq + Serialize, V: Serialize + Clone, S: FnMut(&K) -> V> DiskCache<K, V, S> {
+// non-sync insert is mut, while sync is immute
+impl<K: Serialize + Clone + PartialEq, V: Serialize + Clone, S: FnMut(&K) -> V> DiskCache<K, V, S> {
+    #[allow(dead_code)]
     pub fn get_or_insert_from_supplier(&mut self, k: K) -> V {
+        self.entries.get_or_insert_with(k, |k| (self.supplier)(k))
+    }
+}
+impl<K: Serialize + Clone + PartialEq, V: Serialize + Clone, S: Fn(&K) -> V> SyncDiskCache<K, V, S> {
+    #[allow(dead_code)]
+    pub fn get_or_insert_from_supplier(&self, k: K) -> V {
+        self.entries.get_or_insert_with(k, |k| (self.supplier)(k))
+    }
+}
+
+//---------- disk cache entries ----------
+// we have the non-sync and the sync K/V collections,
+// which the DiskCacheImpl wraps.
+
+pub struct Entries<K, V>(Vec<(K, V)>);
+pub struct SyncEntries<K, V>(RwLock<Entries<K, V>>);
+
+pub trait EntriesCap {
+    type Key;
+    type Value;
+
+    fn from_vec(v: Vec<(Self::Key, Self::Value)>) -> Self;
+    fn to_vec(&self) -> Vec<(Self::Key, Self::Value)>
+    where
+        Self::Key: Clone,
+        Self::Value: Clone;
+    fn get(&self, k: &Self::Key) -> Option<Self::Value>
+    where
+        Self::Key: PartialEq,
+        Self::Value: Clone;
+}
+
+impl<K, V> EntriesCap for Entries<K, V> {
+    type Key = K;
+    type Value = V;
+    fn from_vec(v: Vec<(K, V)>) -> Self {
+        Self(v)
+    }
+    fn to_vec(&self) -> Vec<(K, V)>
+    where
+        K: Clone,
+        V: Clone,
+    {
+        self.0.clone()
+    }
+    fn get(&self, k: &K) -> Option<V>
+    where
+        K: PartialEq,
+        V: Clone,
+    {
+        self.0.iter().find(|(comp_k, _v): &&(K, V)| comp_k == k).map(|(_k, v)| v.clone())
+    }
+}
+
+impl<K, V> EntriesCap for SyncEntries<K, V> {
+    type Key = K;
+    type Value = V;
+    fn from_vec(v: Vec<(K, V)>) -> Self {
+        Self(RwLock::new(Entries::from_vec(v)))
+    }
+    fn to_vec(&self) -> Vec<(K, V)>
+    where
+        K: Clone,
+        V: Clone,
+    {
+        self.0.read().unwrap().to_vec()
+    }
+    fn get(&self, k: &K) -> Option<V>
+    where
+        K: PartialEq,
+        V: Clone,
+    {
+        self.0.read().unwrap().get(k)
+    }
+}
+
+impl<K: PartialEq, V> Entries<K, V> {
+    fn insert(&mut self, k: K, v: V) {
+
+        if !self.0.iter().any(|(comp_k, _v): &(K, V)| comp_k == &k) {
+            self.0.push((k, v))
+        }
+    }
+}
+impl<K: Clone + PartialEq, V: Clone> Entries<K, V> {
+    #[allow(dead_code)]
+    pub fn get_or_insert_with<F: FnOnce(&K) -> V>(&mut self, k: K, f: F) -> V {
         if let Some(v) = self.get(&k) {
-            trace!("get_or_insert_from_supplier hit");
             return v.clone();
         }
 
-        trace!("get_or_insert_from_supplier miss");
-        let v = (self.supplier)(&k);
+        let v = f(&k);
+        self.insert(k, v.clone());
+        v
+    }
+}
+
+impl<K: PartialEq, V> SyncEntries<K, V> {
+    fn insert(&self, k: K, v: V) {
+        self.0.write().unwrap().insert(k, v)
+    }
+}
+impl<K: Clone + PartialEq, V: Clone> SyncEntries<K, V> {
+    #[allow(dead_code)]
+    pub fn get_or_insert_with<F: FnOnce(&K) -> V>(&self, k: K, f: F) -> V {
+        if let Some(v) = self.get(&k) {
+            return v.clone();
+        }
+
+        let v = f(&k);
         self.insert(k, v.clone());
         v
     }
diff --git a/crates/applications/buffer_proto5/src/main.rs b/crates/applications/buffer_proto5/src/main.rs
index 36ba08c..9ffe251 100644
--- a/crates/applications/buffer_proto5/src/main.rs
+++ b/crates/applications/buffer_proto5/src/main.rs
@@ -24,10 +24,11 @@ use coremem::sim::spirv::{SpirvSim, WgpuBackend};
 use coremem::sim::units::{Seconds, Time as _};
 use coremem::stim::{CurlVectorField, Exp, ModulatedVectorField, Sinusoid, TimeVaryingExt as _};
 use log::{error, info, warn};
+use rayon::prelude::*;
 use serde::{Deserialize, Serialize};
 
 mod cache;
-use cache::DiskCache;
+use cache::SyncDiskCache;
 
 type Mat = IsoConductorOr<f32, Ferroxcube3R1MH>;
 
@@ -673,7 +674,7 @@ fn main() {
         variants.len() / post_times.len(),
     );
 
-    let mut geom_cache = DiskCache::new_with_supplier(
+    let mut geom_cache = SyncDiskCache::new_with_supplier(
         &format!("{}/.geom_cache", ensure_out_dir(i)),
         |geom: &GeomParams| derive_geometries(geom.clone())
     );
@@ -719,7 +720,7 @@ fn main() {
         };
 
         let wraps1_choices: Vec<_> = (-120..120)
-            .into_iter()
+            .into_par_iter()
             .filter_map(|wraps1| {
                 let params = GeomParams {
                     wraps1: (wraps1 * 4) as f32,