diff --git a/faiss/CMakeLists.txt b/faiss/CMakeLists.txt
index 33e1849568..9cb1bb6d32 100644
--- a/faiss/CMakeLists.txt
+++ b/faiss/CMakeLists.txt
@@ -51,6 +51,7 @@ set(FAISS_SRC
   VectorTransform.cpp
   clone_index.cpp
   index_factory.cpp
+  FaissHook.cpp
   impl/AuxIndexStructures.cpp
   impl/CodePacker.cpp
   impl/IDSelector.cpp
@@ -145,6 +146,7 @@ set(FAISS_HEADERS
   clone_index.h
   index_factory.h
   index_io.h
+  FaissHook.h
   impl/AdditiveQuantizer.h
   impl/AuxIndexStructures.h
   impl/CodePacker.h
diff --git a/faiss/FaissHook.cpp b/faiss/FaissHook.cpp
new file mode 100644
index 0000000000..47c5bcfc3f
--- /dev/null
+++ b/faiss/FaissHook.cpp
@@ -0,0 +1,40 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// -*- c++ -*-
+
+#include "FaissHook.h"
+
+namespace faiss {
+
+extern float fvec_L2sqr_default(const float* x, const float* y, size_t d);
+
+extern float fvec_inner_product_default(
+        const float* x,
+        const float* y,
+        size_t d);
+
+FVEC_L2SQR_HOOK fvec_L2sqr_hook = fvec_L2sqr_default;
+FVEC_INNER_PRODUCT_HOOK fvec_inner_product_hook = fvec_inner_product_default;
+
+void set_fvec_L2sqr_hook(FVEC_L2SQR_HOOK_C hook) {
+    if (nullptr != hook)
+        fvec_L2sqr_hook = hook;
+}
+FVEC_L2SQR_HOOK_C get_fvec_L2sqr_hook() {
+    return fvec_L2sqr_hook;
+}
+
+void set_fvec_inner_product_hook(FVEC_INNER_PRODUCT_HOOK_C hook) {
+    if (nullptr != hook)
+        fvec_inner_product_hook = hook;
+}
+FVEC_INNER_PRODUCT_HOOK_C get_fvec_inner_product_hook() {
+    return fvec_inner_product_hook;
+}
+
+} // namespace faiss
diff --git a/faiss/FaissHook.h b/faiss/FaissHook.h
new file mode 100644
index 0000000000..0ae9c41020
--- /dev/null
+++ b/faiss/FaissHook.h
@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// -*- c++ -*-
+
+#pragma once
+
+#include <cstddef>
+#include "faiss/impl/platform_macros.h"
+
+namespace faiss {
+
+using FVEC_L2SQR_HOOK = float (*)(const float*, const float*, size_t);
+
+using FVEC_INNER_PRODUCT_HOOK = float (*)(const float*, const float*, size_t);
+
+extern FVEC_L2SQR_HOOK fvec_L2sqr_hook;
+extern FVEC_INNER_PRODUCT_HOOK fvec_inner_product_hook;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef float (*FVEC_L2SQR_HOOK_C)(const float*, const float*, size_t);
+typedef float (*FVEC_INNER_PRODUCT_HOOK_C)(const float*, const float*, size_t);
+
+FAISS_API void set_fvec_L2sqr_hook(FVEC_L2SQR_HOOK_C hook);
+FAISS_API FVEC_L2SQR_HOOK_C get_fvec_L2sqr_hook();
+
+FAISS_API void set_fvec_inner_product_hook(FVEC_INNER_PRODUCT_HOOK_C hook);
+FAISS_API FVEC_INNER_PRODUCT_HOOK_C get_fvec_inner_product_hook();
+
+#ifdef __cplusplus
+}
+#endif
+
+} // namespace faiss
diff --git a/faiss/utils/distances_simd.cpp b/faiss/utils/distances_simd.cpp
index 323859f43b..02b107d73f 100644
--- a/faiss/utils/distances_simd.cpp
+++ b/faiss/utils/distances_simd.cpp
@@ -15,6 +15,7 @@
 #include <cstdio>
 #include <cstring>
 
+#include <faiss/FaissHook.h>
 #include <faiss/impl/FaissAssert.h>
 #include <faiss/impl/platform_macros.h>
 #include <faiss/utils/simdlib.h>
@@ -186,7 +187,7 @@ void fvec_inner_products_ny_ref(
  */
 
 FAISS_PRAGMA_IMPRECISE_FUNCTION_BEGIN
-float fvec_inner_product(const float* x, const float* y, size_t d) {
+float fvec_inner_product_default(const float* x, const float* y, size_t d) {
     float res = 0.F;
     FAISS_PRAGMA_IMPRECISE_LOOP
     for (size_t i = 0; i != d; ++i) {
@@ -196,6 +197,10 @@ float fvec_inner_product(const float* x, const float* y, size_t d) {
 }
 FAISS_PRAGMA_IMPRECISE_FUNCTION_END
 
+float fvec_inner_product(const float* x, const float* y, size_t d) {
+    return fvec_inner_product_hook(x, y, d);
+}
+
 FAISS_PRAGMA_IMPRECISE_FUNCTION_BEGIN
 float fvec_norm_L2sqr(const float* x, size_t d) {
     // the double in the _ref is suspected to be a typo. Some of the manual
@@ -210,8 +215,12 @@ float fvec_norm_L2sqr(const float* x, size_t d) {
 }
 FAISS_PRAGMA_IMPRECISE_FUNCTION_END
 
-FAISS_PRAGMA_IMPRECISE_FUNCTION_BEGIN
 float fvec_L2sqr(const float* x, const float* y, size_t d) {
+    return fvec_L2sqr_hook(x, y, d);
+}
+
+FAISS_PRAGMA_IMPRECISE_FUNCTION_BEGIN
+float fvec_L2sqr_default(const float* x, const float* y, size_t d) {
     size_t i;
     float res = 0;
     FAISS_PRAGMA_IMPRECISE_LOOP