add benchmark against numpy in multithreading

Author: Emma Ai

bench/large_array_vs_numpy.py

@@ -0,0 +1,152 @@
+#################################################################################
+# To mimic the scenario that computation is i/o bound and constrained by memory
+#
+# It's a much simplified version that the chunk is computed in a loop,
+# and expression is evaluated in a sequence, which is not true in reality.
+# Neverthless, numexpr outperforms numpy.
+#################################################################################
+"""
+Benchmarking Expression 1:
+NumPy time (threaded over 32 chunks with 2 threads): 4.612313 seconds
+numexpr time (threaded with re_evaluate over 32 chunks with 2 threads): 0.951172 seconds
+numexpr speedup: 4.85x
+----------------------------------------
+Benchmarking Expression 2:
+NumPy time (threaded over 32 chunks with 2 threads): 23.862752 seconds
+numexpr time (threaded with re_evaluate over 32 chunks with 2 threads): 2.182058 seconds
+numexpr speedup: 10.94x
+----------------------------------------
+Benchmarking Expression 3:
+NumPy time (threaded over 32 chunks with 2 threads): 20.594895 seconds
+numexpr time (threaded with re_evaluate over 32 chunks with 2 threads): 2.927881 seconds
+numexpr speedup: 7.03x
+----------------------------------------
+Benchmarking Expression 4:
+NumPy time (threaded over 32 chunks with 2 threads): 12.834101 seconds
+numexpr time (threaded with re_evaluate over 32 chunks with 2 threads): 5.392480 seconds
+numexpr speedup: 2.38x
+----------------------------------------
+"""
+
+import os
+
+os.environ["NUMEXPR_NUM_THREADS"] = "16"
+import numpy as np
+import numexpr as ne
+import timeit
+import threading
+
+array_size = 10**8
+num_runs = 10
+num_chunks = 32  # Number of chunks
+num_threads = 2  # Number of threads constrained by how many chunks memory can hold
+
+a = np.random.rand(array_size).reshape(10**4, -1)
+b = np.random.rand(array_size).reshape(10**4, -1)
+c = np.random.rand(array_size).reshape(10**4, -1)
+
+chunk_size = array_size // num_chunks
+
+expressions_numpy = [
+    lambda a, b, c: a + b * c,
+    lambda a, b, c: a**2 + b**2 - 2 * a * b * np.cos(c),
+    lambda a, b, c: np.sin(a) + np.log(b) * np.sqrt(c),
+    lambda a, b, c: np.exp(a) + np.tan(b) - np.sinh(c),
+]
+
+expressions_numexpr = [
+    "a + b * c",
+    "a**2 + b**2 - 2 * a * b * cos(c)",
+    "sin(a) + log(b) * sqrt(c)",
+    "exp(a) + tan(b) - sinh(c)",
+]
+
+
+def benchmark_numpy_chunk(func, a, b, c, results, indices):
+    for index in indices:
+        start = index * chunk_size
+        end = (index + 1) * chunk_size
+        time_taken = timeit.timeit(
+            lambda: func(a[start:end], b[start:end], c[start:end]), number=num_runs
+        )
+        results.append(time_taken)
+
+
+def benchmark_numexpr_re_evaluate(expr, a, b, c, results, indices):
+    for index in indices:
+        start = index * chunk_size
+        end = (index + 1) * chunk_size
+        if index == 0:
+            # Evaluate the first chunk with evaluate
+            time_taken = timeit.timeit(
+                lambda: ne.evaluate(
+                    expr,
+                    local_dict={
+                        "a": a[start:end],
+                        "b": b[start:end],
+                        "c": c[start:end],
+                    },
+                ),
+                number=num_runs,
+            )
+        else:
+            # Re-evaluate subsequent chunks with re_evaluate
+            time_taken = timeit.timeit(
+                lambda: ne.re_evaluate(
+                    local_dict={"a": a[start:end], "b": b[start:end], "c": c[start:end]}
+                ),
+                number=num_runs,
+            )
+        results.append(time_taken)
+
+
+def run_benchmark_threaded():
+    chunk_indices = list(range(num_chunks))
+
+    for i in range(len(expressions_numpy)):
+        print(f"Benchmarking Expression {i+1}:")
+
+        results_numpy = []
+        results_numexpr = []
+
+        threads_numpy = []
+        for j in range(num_threads):
+            indices = chunk_indices[j::num_threads]  # Distribute chunks across threads
+            thread = threading.Thread(
+                target=benchmark_numpy_chunk,
+                args=(expressions_numpy[i], a, b, c, results_numpy, indices),
+            )
+            threads_numpy.append(thread)
+            thread.start()
+
+        for thread in threads_numpy:
+            thread.join()
+
+        numpy_time = sum(results_numpy)
+        print(
+            f"NumPy time (threaded over {num_chunks} chunks with {num_threads} threads): {numpy_time:.6f} seconds"
+        )
+
+        threads_numexpr = []
+        for j in range(num_threads):
+            indices = chunk_indices[j::num_threads]  # Distribute chunks across threads
+            thread = threading.Thread(
+                target=benchmark_numexpr_re_evaluate,
+                args=(expressions_numexpr[i], a, b, c, results_numexpr, indices),
+            )
+            threads_numexpr.append(thread)
+            thread.start()
+
+        for thread in threads_numexpr:
+            thread.join()
+
+        numexpr_time = sum(results_numexpr)
+        print(
+            f"numexpr time (threaded with re_evaluate over {num_chunks} chunks with {num_threads} threads): {numexpr_time:.6f} seconds"
+        )
+        print(f"numexpr speedup: {numpy_time / numexpr_time:.2f}x")
+        print("-" * 40)
+
+
+if __name__ == "__main__":
+    run_benchmark_threaded()