sync with FB version 2017-11-22

various bugfixes from github issues
kmean with some frozen centroids
GPU better tiling for large flat datasets
default AVX for vector ops

gpu/GpuFaissAssert.h

+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD+Patents license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#ifndef GPU_FAISS_ASSERT_INCLUDED
+#define GPU_FAISS_ASSERT_INCLUDED
+
+#include "../FaissAssert.h"
+#include <cuda.h>
+
+///
+/// Assertions
+///
+
+#ifdef __CUDA_ARCH__
+#define GPU_FAISS_ASSERT(X) assert(X)
+#define GPU_FAISS_ASSERT_MSG(X, MSG) assert(X)
+#define GPU_FAISS_ASSERT_FMT(X, FMT, ...) assert(X)
+#else
+#define GPU_FAISS_ASSERT(X) FAISS_ASSERT(X)
+#define GPU_FAISS_ASSERT_MSG(X, MSG) FAISS_ASSERT_MSG(X, MSG)
+#define GPU_FAISS_ASSERT_FMT(X, FMT, ...) FAISS_ASSERT_FMT(X, FMT, __VA_ARGS)
+#endif // __CUDA_ARCH__
+
+#endif