From be21711c939d1e705edd68b6c6b79f9d3e134143 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B8ren=20Fuglede=20J=C3=B8rgensen?= <github@fuglede.dk>
Date: Wed, 19 Apr 2023 11:45:35 +0200
Subject: [PATCH] Add writeBasis interface method to highspy

---
 highspy/highs_bindings.cpp    |  1 +
 highspy/tests/test_highspy.py | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/highspy/highs_bindings.cpp b/highspy/highs_bindings.cpp
index 4f33c46a7e..dd7c8bd509 100644
--- a/highspy/highs_bindings.cpp
+++ b/highspy/highs_bindings.cpp
@@ -735,6 +735,7 @@ PYBIND11_MODULE(highs_bindings, m)
     .def("passRowName", &Highs::passRowName)
     .def("readModel", &Highs::readModel)
     .def("readBasis", &Highs::readBasis)
+    .def("writeBasis", &Highs::writeBasis)
     .def("presolve", &Highs::presolve)
     .def("run", &Highs::run)
     .def("postsolve", &Highs::postsolve)
diff --git a/highspy/tests/test_highspy.py b/highspy/tests/test_highspy.py
index 80a4516dc1..2c46a0c717 100644
--- a/highspy/tests/test_highspy.py
+++ b/highspy/tests/test_highspy.py
@@ -1,3 +1,4 @@
+import tempfile
 import unittest
 import highspy
 import numpy as np
@@ -404,3 +405,37 @@ def test_ranging(self):
         self.assertEqual(ranging.row_bound_up.value_[1], inf);
         self.assertEqual(ranging.row_bound_up.objective_[1], inf);
         
+    def test_write_basis_before_running(self):
+        h = self.get_basic_model()
+        with tempfile.NamedTemporaryFile() as f:
+            h.writeBasis(f.name)
+            contents = f.read()
+            self.assertEqual(contents, b'HiGHS v1\nNone\n')
+        
+    def test_write_basis_after_running(self):
+        h = self.get_basic_model()
+        h.run()
+        with tempfile.NamedTemporaryFile() as f:
+            h.writeBasis(f.name)
+            contents = f.read()
+            self.assertEqual(
+                contents, b'HiGHS v1\nValid\n# Columns 2\n1 1 \n# Rows 2\n0 0 \n'
+            )
+
+    def test_read_basis(self):
+        # Read basis from one run model into an unrun model
+        expected_status_before = highspy.HighsBasisStatus.kLower
+        expected_status_after = highspy.HighsBasisStatus.kBasic
+
+        h1 = self.get_basic_model()
+        self.assertEqual(h1.getBasis().col_status[0], expected_status_before)
+        h1.run()
+        self.assertEqual(h1.getBasis().col_status[0], expected_status_after)
+
+        h2 = self.get_basic_model()
+        self.assertEqual(h2.getBasis().col_status[0], expected_status_before)
+
+        with tempfile.NamedTemporaryFile() as f:
+            h1.writeBasis(f.name)
+            h2.readBasis(f.name)
+            self.assertEqual(h2.getBasis().col_status[0], expected_status_after)