diff --git a/PORTING.md b/PORTING.md
index 8d7045bf..0db8cb25 100644
--- a/PORTING.md
+++ b/PORTING.md
@@ -59,8 +59,8 @@ Some porting tasks will require other tasks as dependencies, the GitHub issues p
   - [ ] Updates
   - [x] Functors
 - [ ] `gmultiset.v` 
-  - [ ] CMRA
-  - [ ] Updates
+  - [x] CMRA
+  - [x] Updates
 - [ ] `gset.v` 
   - [ ] CMRA
   - [ ] Updates
@@ -430,5 +430,3 @@ Some porting tasks will require other tasks as dependencies, the GitHub issues p
   - [ ] `language.v`
   - [ ] `ectx_language.v`
   - [ ] `ectxi_language.v`
-
-
diff --git a/src/Iris/Algebra.lean b/src/Iris/Algebra.lean
index 30043dc5..e54c4665 100644
--- a/src/Iris/Algebra.lean
+++ b/src/Iris/Algebra.lean
@@ -5,6 +5,7 @@ import Iris.Algebra.DFrac
 import Iris.Algebra.Excl
 import Iris.Algebra.Frac
 import Iris.Algebra.GenMap
+import Iris.Algebra.GMultiset
 import Iris.Algebra.LocalUpdates
 import Iris.Algebra.IProp
 import Iris.Algebra.OFE
diff --git a/src/Iris/Algebra/GMultiset.lean b/src/Iris/Algebra/GMultiset.lean
new file mode 100644
index 00000000..47e0cb6f
--- /dev/null
+++ b/src/Iris/Algebra/GMultiset.lean
@@ -0,0 +1,297 @@
+import Iris.Algebra.CMRA
+import Iris.Algebra.LocalUpdates
+import Iris.Algebra.Updates
+import Iris.Std.HeapInstances
+
+namespace Iris
+
+open OFE CMRA
+open Iris.Std PartialMap LawfulPartialMap
+
+abbrev PosNat := { n : Nat // 0 < n }
+
+structure GMultiset (K : Type _) [Ord K] [Std.TransOrd K] [Std.LawfulEqOrd K] where
+  car : Std.TreeMap K PosNat compare
+
+namespace GMultiset
+
+variable {K : Type _} [Ord K] [Std.TransOrd K] [Std.LawfulEqOrd K]
+
+def equiv (X Y : GMultiset K) : Prop :=
+  ∀ k : K, X.car[k]? = Y.car[k]?
+
+abbrev empty : GMultiset K :=
+  { car := (∅ : Std.TreeMap K PosNat compare) }
+
+instance : OFE (GMultiset K) :=
+  OFE.ofDiscrete equiv (by
+    constructor
+    · intro X k
+      rfl
+    · intro X Y h k
+      exact (h k).symm
+    · intro X Y Z h1 h2 k
+      exact (h1 k).trans (h2 k))
+
+@[simp] theorem equiv_def {X Y : GMultiset K} : X ≡ Y ↔ ∀ k : K, X.car[k]? = Y.car[k]? :=
+  Iff.rfl
+
+instance : OFE.Discrete (GMultiset K) where
+  discrete_0 h := h
+
+private def addCounts (_ : K) (n m : PosNat) : PosNat :=
+  ⟨n.1 + m.1, Nat.add_pos_left n.2 _⟩
+
+private def optCount : Option PosNat → Nat
+  | none => 0
+  | some n => n.1
+
+private theorem optCount_inj {a b : Option PosNat} : optCount a = optCount b → a = b := by
+  intro h
+  cases a with
+  | none =>
+      cases b with
+      | none => rfl
+      | some b => exact False.elim <| Nat.ne_of_gt b.property h.symm
+  | some a =>
+      cases b with
+      | none => exact False.elim <| Nat.ne_of_gt a.property h
+      | some b =>
+          apply congrArg some
+          exact Subtype.ext h
+
+omit [Ord K] [Std.TransOrd K] [Std.LawfulEqOrd K] in
+private theorem optCount_merge {K : Type _} (k : K) (a b : Option PosNat) :
+    optCount (Option.merge (addCounts k) a b) = optCount a + optCount b := by
+  cases a <;> cases b <;> simp [optCount, Option.merge, addCounts]
+
+omit [Ord K] [Std.TransOrd K] [Std.LawfulEqOrd K] in
+private theorem optMerge_assoc {K : Type _} (k : K) (a b c : Option PosNat) :
+    Option.merge (addCounts k) a (Option.merge (addCounts k) b c) =
+      Option.merge (addCounts k) (Option.merge (addCounts k) a b) c := by
+  apply optCount_inj
+  simp [optCount_merge, Nat.add_assoc]
+
+omit [Ord K] [Std.TransOrd K] [Std.LawfulEqOrd K] in
+private theorem optMerge_comm {K : Type _} (k : K) (a b : Option PosNat) :
+    Option.merge (addCounts k) a b = Option.merge (addCounts k) b a := by
+  apply optCount_inj
+  simp [optCount_merge, Nat.add_comm]
+
+omit [Ord K] [Std.TransOrd K] [Std.LawfulEqOrd K] in
+private theorem optMerge_right_cancel {K : Type _} (k : K) {a b c : Option PosNat} :
+    Option.merge (addCounts k) a c = Option.merge (addCounts k) b c → a = b := by
+  intro h
+  have hc := congrArg optCount h
+  rw [optCount_merge, optCount_merge] at hc
+  exact optCount_inj (Nat.add_right_cancel hc)
+
+omit [Ord K] [Std.TransOrd K] [Std.LawfulEqOrd K] in
+private theorem optMerge_left_cancel {K : Type _} (k : K) {a b c : Option PosNat} :
+    Option.merge (addCounts k) c a = Option.merge (addCounts k) c b → a = b := by
+  intro h
+  apply optMerge_right_cancel (k := k) (c := c)
+  calc
+    Option.merge (addCounts k) a c = Option.merge (addCounts k) c a := optMerge_comm k _ _
+    _ = Option.merge (addCounts k) c b := h
+    _ = Option.merge (addCounts k) b c := optMerge_comm k _ _
+
+private abbrev opG (X Y : GMultiset K) : GMultiset K :=
+  { car := Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts X.car Y.car }
+
+private theorem get?_opG (X Y : GMultiset K) (k : K) :
+    Iris.Std.get? (M := fun V => Std.TreeMap K V compare) (opG X Y).car k =
+      Option.merge (addCounts k)
+        (Iris.Std.get? (M := fun V => Std.TreeMap K V compare) X.car k)
+        (Iris.Std.get? (M := fun V => Std.TreeMap K V compare) Y.car k) := by
+  change Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+      (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts X.car Y.car) k =
+    Option.merge (addCounts k)
+      (Iris.Std.get? (M := fun V => Std.TreeMap K V compare) X.car k)
+      (Iris.Std.get? (M := fun V => Std.TreeMap K V compare) Y.car k)
+  rw [LawfulPartialMap.get?_merge]
+
+private theorem empty_op_empty_eqv :
+    (empty (K := K)) ≡ opG (empty (K := K)) (empty (K := K)) := by
+  intro k
+  change none = Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+    (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts
+      ((∅ : Std.TreeMap K PosNat compare)) ((∅ : Std.TreeMap K PosNat compare))) k
+  have h0 : Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+      ((∅ : Std.TreeMap K PosNat compare)) k = none :=
+    LawfulPartialMap.get?_empty (M := fun V => Std.TreeMap K V compare) (K := K) k
+  rw [LawfulPartialMap.get?_merge]
+  simp [h0, Option.merge]
+
+private theorem op_assoc_eqv (X Y Z : GMultiset K) :
+    opG X (opG Y Z) ≡ opG (opG X Y) Z := by
+  intro k
+  change (Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+      (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts X.car
+        (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts Y.car Z.car)) k =
+    Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+      (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts
+        (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts X.car Y.car) Z.car) k)
+  repeat rw [LawfulPartialMap.get?_merge]
+  exact optMerge_assoc k _ _ _
+
+private theorem op_comm_eqv (X Y : GMultiset K) :
+    opG X Y ≡ opG Y X := by
+  intro k
+  change (Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+      (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts X.car Y.car) k =
+    Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+      (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts Y.car X.car) k)
+  repeat rw [LawfulPartialMap.get?_merge]
+  exact optMerge_comm k _ _
+
+instance opG_ne (x : GMultiset K) : NonExpansive (opG x) where
+  ne := by
+    intro n Y1 Y2 h k
+    change Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+      (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts x.car Y1.car) k =
+      Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+        (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts x.car Y2.car) k
+    repeat rw [LawfulPartialMap.get?_merge]
+    simpa [addCounts] using
+      congrArg (Option.merge (addCounts k)
+        (Iris.Std.get? (M := fun V => Std.TreeMap K V compare) x.car k)) (h k)
+
+instance : CMRA (GMultiset K) where
+  pcore _ := some (empty (K := K))
+  op := opG
+  ValidN _ _ := True
+  Valid _ := True
+
+  op_ne := inferInstance
+  pcore_ne := by
+    intro n X Y h cx hcx
+    cases hcx
+    exact ⟨empty (K := K), rfl, Dist.rfl⟩
+  validN_ne {n x y} := by
+    intro _ _
+    trivial
+
+  valid_iff_validN {x} := ⟨fun _ _ => trivial, fun _ => trivial⟩
+  validN_succ {n x} := by intro _; trivial
+  validN_op_left {n x y} := by intro _; trivial
+
+  assoc := op_assoc_eqv _ _ _
+  comm := op_comm_eqv _ _
+
+  pcore_op_left {x cx} := by
+    intro hcx i
+    cases hcx
+    change (Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+      (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts
+        ((∅ : Std.TreeMap K PosNat compare)) x.car) i =
+      Iris.Std.get? (M := fun V => Std.TreeMap K V compare) x.car i)
+    have h0 : Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+        ((∅ : Std.TreeMap K PosNat compare)) i = none :=
+      LawfulPartialMap.get?_empty (M := fun V => Std.TreeMap K V compare) (K := K) i
+    rw [LawfulPartialMap.get?_merge, h0]
+    cases hx : Iris.Std.get? (M := fun V => Std.TreeMap K V compare) x.car i <;>
+      simp [Option.merge]
+  pcore_idem {x cx} := by
+    intro hcx
+    have : cx = empty (K := K) := Option.some.inj hcx.symm
+    subst this
+    exact Equiv.rfl
+  pcore_op_mono {x cx} := by
+    intro hcx y
+    cases hcx
+    refine ⟨empty (K := K), ?_⟩
+    exact OFE.some_eqv_some.mpr empty_op_empty_eqv
+  extend {n x y1 y2} := by
+    intro _ h
+    exact ⟨y1, ⟨y2, h, Dist.rfl, Dist.rfl⟩⟩
+
+instance : CMRA.Discrete (GMultiset K) where
+  discrete_valid {x} := by
+    intro _; trivial
+
+instance : UCMRA (GMultiset K) where
+  unit := empty (K := K)
+  unit_valid := trivial
+  unit_left_id {x} := by
+    intro i
+    change (Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+      (Iris.Std.merge (M := fun V => Std.TreeMap K V compare) (K := K) addCounts
+        ((∅ : Std.TreeMap K PosNat compare)) x.car) i =
+      Iris.Std.get? (M := fun V => Std.TreeMap K V compare) x.car i)
+    have h0 : Iris.Std.get? (M := fun V => Std.TreeMap K V compare)
+        ((∅ : Std.TreeMap K PosNat compare)) i = none :=
+      LawfulPartialMap.get?_empty (M := fun V => Std.TreeMap K V compare) (K := K) i
+    rw [LawfulPartialMap.get?_merge, h0]
+    cases hx : Iris.Std.get? (M := fun V => Std.TreeMap K V compare) x.car i <;>
+      simp [Option.merge]
+  pcore_unit := by
+    rfl
+
+theorem gMultiset_update (X Y : GMultiset K) : X ~~> Y := by
+  intro _ _ _
+  trivial
+
+@[simp] theorem get?_op (X Y : GMultiset K) (k : K) :
+    Iris.Std.get? (M := fun V => Std.TreeMap K V compare) (X • Y).car k =
+      Option.merge (addCounts k)
+        (Iris.Std.get? (M := fun V => Std.TreeMap K V compare) X.car k)
+        (Iris.Std.get? (M := fun V => Std.TreeMap K V compare) Y.car k) := by
+  show Iris.Std.get? (M := fun V => Std.TreeMap K V compare) (opG X Y).car k =
+      Option.merge (addCounts k)
+        (Iris.Std.get? (M := fun V => Std.TreeMap K V compare) X.car k)
+        (Iris.Std.get? (M := fun V => Std.TreeMap K V compare) Y.car k)
+  exact get?_opG X Y k
+
+theorem gMultiset_localUpdate {X Y X' Y' : GMultiset K}
+    (hxy : X • Y' ≡ X' • Y) :
+    (X, Y) ~l~> (X', Y') := by
+  refine (local_update_unital_discrete X Y X' Y').mpr ?_
+  intro Z _ hXZ
+  refine ⟨trivial, ?_⟩
+  intro k
+  let f : Option PosNat → Option PosNat → Option PosNat := Option.merge (addCounts k)
+  have hxyk0 :
+      Iris.Std.get? (M := fun V => Std.TreeMap K V compare) (X' • Y).car k =
+        Iris.Std.get? (M := fun V => Std.TreeMap K V compare) (X • Y').car k := by
+    exact (hxy k).symm
+  have hxyk : f X'.car[k]? Y.car[k]? = f X.car[k]? Y'.car[k]? := by
+    simpa [f] using hxyk0
+  have hXZk0 :
+      Iris.Std.get? (M := fun V => Std.TreeMap K V compare) X.car k =
+        Iris.Std.get? (M := fun V => Std.TreeMap K V compare) (Y • Z).car k := by
+    exact hXZ k
+  have hXZk : X.car[k]? = f Y.car[k]? Z.car[k]? := by
+    simpa [f] using hXZk0
+  have hstep : f X'.car[k]? Y.car[k]? = f (f Y'.car[k]? Z.car[k]?) Y.car[k]? := by
+    calc
+      f X'.car[k]? Y.car[k]? = f X.car[k]? Y'.car[k]? := hxyk
+      _ = f (f Y.car[k]? Z.car[k]?) Y'.car[k]? := by rw [hXZk]
+      _ = f Y.car[k]? (f Z.car[k]? Y'.car[k]?) := (optMerge_assoc k _ _ _).symm
+      _ = f Y.car[k]? (f Y'.car[k]? Z.car[k]?) := by
+            simpa [f] using congrArg (f Y.car[k]?) (optMerge_comm k Z.car[k]? Y'.car[k]?)
+      _ = f (f Y'.car[k]? Z.car[k]?) Y.car[k]? := optMerge_comm k _ _
+  have hfinal :=
+    optMerge_right_cancel (k := k) (a := X'.car[k]?) (b := f Y'.car[k]? Z.car[k]?) (c := Y.car[k]?) hstep
+  change Iris.Std.get? (M := fun V => Std.TreeMap K V compare) X'.car k =
+    Iris.Std.get? (M := fun V => Std.TreeMap K V compare) (Y' • Z).car k
+  simpa [f] using hfinal
+
+instance (X : GMultiset K) : Cancelable X where
+  cancelableN {n y z} _ h := by
+    intro k
+    have hk : Iris.Std.get? (M := fun V => Std.TreeMap K V compare) (X • y).car k =
+        Iris.Std.get? (M := fun V => Std.TreeMap K V compare) (X • z).car k := h k
+    rw [get?_op, get?_op] at hk
+    exact optMerge_left_cancel (k := k) hk
+
+theorem gMultiset_localUpdate_alloc (X Y X' : GMultiset K) :
+    (X, Y) ~l~> (X • X', Y • X') := by
+  apply gMultiset_localUpdate
+  calc
+    X • (Y • X') ≡ X • (X' • Y) := by exact (comm (x := Y) (y := X')).op_r
+    _ ≡ (X • X') • Y := assoc
+
+end GMultiset
+
+end Iris