From 3c713bab5046d212e6f6924e794effb15f35a1f3 Mon Sep 17 00:00:00 2001
From: Chenyang Yuan <yuanchenyang@gmail.com>
Date: Sat, 5 Oct 2024 18:41:19 -0400
Subject: [PATCH] Performance improvement in creating Basis objects

---
 .gitignore                |  2 +-
 src/SumOfSquares/SoS.py   |  2 +-
 src/SumOfSquares/basis.py | 18 ++++++++++++------
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/.gitignore b/.gitignore
index c48336c..fa5eb2c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,7 +14,7 @@ __pycache__
 *.out
 
 # Project specific
-/Untitled.ipynb
+/examples
 /.ipynb_checkpoints/
 /build/
 /dist/
diff --git a/src/SumOfSquares/SoS.py b/src/SumOfSquares/SoS.py
index 7a53dcc..8e8d256 100644
--- a/src/SumOfSquares/SoS.py
+++ b/src/SumOfSquares/SoS.py
@@ -162,7 +162,7 @@ def poly_opt_prob(vars       : List[sp.Symbol],
                   deg        : Optional[int] = None,
                   sparse     : bool = False) -> SOSProblem:
     '''Formulates and returns a degree DEG Sum-of-Squares relaxation of a polynomial
-    optimization problem in variables VARS that mininizes OBJ subject to
+    optimization problem in variables VARS that minimizes OBJ subject to
     equality constraints EQS (g(x) = 0) and inequality constraints INEQS (h(x)
     >= 0). INEQ_PRODS determines if products of inequalities are used. SPARSE
     uses Newton polytope reduction to do computations in a reduced-size
diff --git a/src/SumOfSquares/basis.py b/src/SumOfSquares/basis.py
index 9e2072b..322f044 100644
--- a/src/SumOfSquares/basis.py
+++ b/src/SumOfSquares/basis.py
@@ -3,6 +3,7 @@
 import sympy as sp
 import numpy as np
 import math
+from functools import lru_cache
 from collections import defaultdict
 from typing import Iterable, Tuple, List, Union
 
@@ -39,12 +40,6 @@ def __init__(self, monoms: List[Tuple[int]]):
         self.nvars = len(monoms[0])
         self.is_hom = sum(sum(m) != self.deg for m in self.monoms) == 0
 
-        # A map from a monomial m (represented as tuple) to list of pairs (i, j)
-        # for all such pairs where m = basis[i]*basis[j].
-        self.sos_sym_entries = defaultdict(list)
-        for i, bi in enumerate(self):
-            for j, bj in enumerate(self):
-                 self.sos_sym_entries[sum_tuple(bi, bj)].append((i, j))
 
     def __len__(self) -> int:
         return len(self.monoms)
@@ -52,6 +47,17 @@ def __len__(self) -> int:
     def __iter__(self) -> Iterable[Tuple[int]]:
         return iter(self.monoms)
 
+    @property
+    @lru_cache()
+    def sos_sym_entries(self):
+        # A map from a monomial m (represented as tuple) to list of pairs (i, j)
+        # for all such pairs where m = basis[i]*basis[j].
+        sos_sym_entries = defaultdict(list)
+        for i, bi in enumerate(self):
+            for j, bj in enumerate(self):
+                 sos_sym_entries[sum_tuple(bi, bj)].append((i, j))
+        return sos_sym_entries
+
     def from_degree(nvars: int, deg: int, hom: bool=False) -> Basis:
         '''Constructs a basis by specifying the number of variables and degree'''
         return Basis(list((basis_hom if hom else basis_inhom)(nvars, deg)))