Add performance test

.github/workflows/python-package.yml

@@ -39,6 +39,14 @@ jobs:
         flags: ${{ matrix.os }}-${{ matrix.python-version }}
       env:
         CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+    - name: Benchmarking upload to Codspeed
+      if: matrix.python-version == '3.12' && matrix.os == 'ubuntu-latest'
+      uses: CodSpeedHQ/action@v3
+      with:
+        run: |
+          cd tests
+          python -m pytest --codspeed
+        token: ${{ secrets.CODSPEED_TOKEN }}
   test_without_numpy:
     name: Test without numpy
     runs-on: ubuntu-latest

CHANGES.rst

@@ -13,6 +13,15 @@ Changes
    execute it, a `NotImplementedError` is raised indicating that the
    function can't be used because `numpy` couldn't be imported.
 
+Adds:
+
+- Added a small benchmarking suite to CI to guard against absolute performance
+   regressions and accidental breakage of the lazy expansion algorithm whichs ensures
+   O(N), rather than O(N^2), scaling complexity for operations involving many numbers
+   with uncertainty. Established connectivity with `codspeed.io<codspeed.io>`_ to track
+   benchmarking results. (#274)
+
+
 Fixes:
 
 - fix `readthedocs` configuration so that the build passes (#254)

pyproject.toml

@@ -62,7 +62,7 @@ Changelog = "https://github.com/lmfit/uncertainties/blob/master/CHANGES.rst"
 
 [project.optional-dependencies]
 arrays = ["numpy"]
-test = ["pytest", "pytest_cov"]
+test = ["pytest", "pytest_codspeed", "pytest_cov"]
 doc = ["sphinx", "sphinx-copybutton", "python-docs-theme"]
 all = ["uncertainties[doc,test,arrays]"]
 

tests/test_performance.py

@@ -0,0 +1,57 @@
+from math import log10
+import time
+import timeit
+
+import pytest
+
+from uncertainties import ufloat
+
+
+def repeated_summation(num):
+    """
+    generate and sum many floats together, then calculate the standard deviation of the
+    output. Under the lazy expansion algorithm, the uncertainty remains non-expanded
+    until a request is made to calculate the standard deviation.
+    """
+    result = sum(ufloat(1, 0.1) for _ in range(num)).std_dev
+    return result
+
+
+def test_repeated_summation_complexity():
+    """
+    Test that the execution time is linear in summation length
+    """
+    approx_execution_time_per_n = 10e-6  # 10 us
+    target_test_duration = 1  # 1 s
+
+    n_list = [10, 100, 1000, 10000, 100000]
+    t_list = []
+    for n in n_list:
+        """
+        Choose the number of repetitions so that the test takes target_test_duration
+        assuming the timing of a single run is approximately
+        N * approx_execution_time_per_n
+        """
+        # Choose the number of repetitions so that the test
+        single_rep_duration = n * approx_execution_time_per_n
+        num_reps = int(target_test_duration / single_rep_duration)
+
+        t_tot = timeit.timeit(
+            lambda: repeated_summation(n),
+            number=num_reps,
+            timer=time.process_time,
+        )
+        t_single = t_tot / num_reps
+        t_list.append(t_single)
+    n0 = n_list[0]
+    t0 = t_list[0]
+    for n, t in zip(n_list[1:], t_list[1:]):
+        # Check that the plot of t vs n is linear on a log scale to within 10%
+        # See PR 275
+        assert 0.9 * log10(n / n0) < log10(t / t0) < 1.1 * log10(n / n0)
+
+
+@pytest.mark.parametrize("num", (10, 100, 1000, 10000, 100000))
+@pytest.mark.benchmark
+def test_repeated_summation_speed(num):
+    repeated_summation(num)