Compare array access pattern performance

Author: rafmudaf

array_access_patterns.py

@@ -0,0 +1,85 @@
+
+import gc
+import numpy as np
+import time
+
+# contiguous_array[i-1]
+# contiguous_array[i]
+# contiguous_array[i+1]
+# new_array1 = np.ones(np.shape(contiguous_array))
+
+print("Configuration")
+# Python float is 64 bit / 8 byte
+ARRAY_SIZE = 1000 * 1000 * 1
+print("- Size of data array: {} MB".format(ARRAY_SIZE * 8 / (1000 * 1000)))
+
+N = 10
+print("- Number of iterations to average: {}".format(N))
+
+def SETUP():
+    array1 = np.ones(ARRAY_SIZE)
+    array2 = np.ones(ARRAY_SIZE)
+    buffer_array = np.empty(ARRAY_SIZE)
+    return array1, array2, buffer_array
+
+
+if __name__=="__main__":
+    # gc.disable()
+
+    print("{:45}{:<15}{:<15}".format("Case description", "Total time", "Per-iteration time"))
+    
+    array1, array2, buffer_array = SETUP()
+    index_map = np.random.randint(0, ARRAY_SIZE - 1, size=ARRAY_SIZE)
+    elapsed_time = 0.0
+    for _ in range(N):
+        start = time.time()
+
+        for i in index_map:
+            buffer_array[i] = array1[i] + array2[i]
+
+        end = time.time()
+        elapsed_time += end - start
+    average = elapsed_time / N
+    print("{:45}{:<15.6f}{:<15.6f}".format("Non-contiguous access, no vectorization", elapsed_time, average))
+
+
+    array1, array2, buffer_array = SETUP()
+    elapsed_time = 0.0
+    for _ in range(N):
+        start = time.time()
+
+        for i in range(ARRAY_SIZE):
+            buffer_array[i] = array1[i] + array2[i]
+
+        end = time.time()
+        elapsed_time += end - start
+    average = elapsed_time / N
+    print("{:45}{:<15.6f}{:<15.6f}".format("Contiguous access, no vectorization", elapsed_time, average))
+
+
+    array1, array2, buffer_array = SETUP()
+    index_map = np.random.randint(0, ARRAY_SIZE - 1, size=ARRAY_SIZE)
+    elapsed_time = 0.0
+    for _ in range(N):
+        start = time.time()
+
+        buffer_array = array1[index_map] + array2[index_map]
+
+        end = time.time()
+        elapsed_time += end - start
+    average = elapsed_time / N
+    print("{:45}{:<15.6f}{:<15.6f}".format("Non-contiguous access, vectorization", elapsed_time, average))
+
+
+    array1, array2, buffer_array = SETUP()
+    index_map = np.arange(0, ARRAY_SIZE)
+    elapsed_time = 0.0
+    for _ in range(N):
+        start = time.time()
+
+        buffer_array = array1[index_map] + array2[index_map]
+
+        end = time.time()
+        elapsed_time += end - start
+    average = elapsed_time / N
+    print("{:45}{:<15.6f}{:<15.6f}".format("Contiguous access, vectorization", elapsed_time, average))