Exact search perf with OpenBLAS.

gistfile1.txt

In [1]: import numpy as np

In [2]: import faiss
Failed to load GPU Faiss: No module named swigfaiss_gpu
Faiss falling back to CPU-only.

In [3]: import time

In [4]:

In [4]: # d = 160

In [5]: d = 128

In [6]: X = np.random.random((1000000, d)).astype('float32')

In [7]:

In [7]: index = faiss.IndexFlatL2(d)

In [8]:

In [8]: index.add(X)

In [9]:

In [9]: t0 = time.time(); index.search(X[:19], 20); print time.time() - t0
0.0915608406067

In [10]:

In [10]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.513067960739

In [11]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
2.2951130867

In [12]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.477697849274

In [13]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
5.21513700485

In [14]: faiss.omp_set_num_threads(1)

In [15]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.331252098083

In [16]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.32853102684

In [17]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.333997964859

In [18]: faiss.omp_set_num_threads(20)

In [19]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.46444106102

In [20]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.452957868576

In [21]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.461181879044

In [22]: faiss.omp_set_num_threads(40)

In [23]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
5.00787210464

In [24]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
4.98109602928

In [25]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
4.99316191673

In [26]: faiss.omp_set_num_threads(20)

In [27]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.458247900009

In [28]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.453998088837

In [29]: faiss.omp_set_num_threads(1)

In [30]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.315454006195

In [31]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.342401027679

In [32]: t0 = time.time(); index.search(X[:20], 20); print time.time() - t0
0.32044506073