diff --git a/acinclude/ax_check_cpu.m4 b/acinclude/ax_check_cpu.m4
index d0a04a770..fc61fc91e 100644
--- a/acinclude/ax_check_cpu.m4
+++ b/acinclude/ax_check_cpu.m4
@@ -3,24 +3,22 @@
 AC_DEFUN([AX_CPU_ARCH], [
 
 AC_MSG_CHECKING([for cpu arch])
-AC_CANONICAL_TARGET
 
-case $target in
-  amd64-* | x86_64-*)
-    ARCH_CPUFLAGS="-mpopcnt"
-    ARCH_CXXFLAGS="-m64"
+  AC_CANONICAL_TARGET
 
-    AX_GCC_X86_CPU_SUPPORTS(avx2,
-        [ARCH_CPUFLAGS+=" -mavx2 -mf16c"],
-        [ARCH_CPUFLAGS+=" -msse4"])
-    ;;
-  aarch64*-*)
+  case $target in
+    amd64-* | x86_64-*)
+      ARCH_CPUFLAGS="-mpopcnt -msse4"
+      ARCH_CXXFLAGS="-m64"
+      ;;
+    aarch64*-*)
 dnl This is an arch for Nvidia Xavier a proper detection would be nice.
-    ARCH_CPUFLAGS="-march=armv8.2-a"
-    ;;
-  *) ;;
-esac
-AC_MSG_RESULT([$target CPUFLAGS+=$ARCH_CPUFLAGS CXXFLAGS+=$ARCH_CXXFLAGS])
+      ARCH_CPUFLAGS="-march=armv8.2-a"
+      ;;
+    *) ;;
+  esac
+
+AC_MSG_RESULT([$target CPUFLAGS+="$ARCH_CPUFLAGS" CXXFLAGS+="$ARCH_CXXFLAGS"])
 
 AC_SUBST(ARCH_CPUFLAGS)
 AC_SUBST(ARCH_CXXFLAGS)
diff --git a/acinclude/ax_gcc_x86_cpu_supports.m4 b/acinclude/ax_gcc_x86_cpu_supports.m4
deleted file mode 100644
index fd37b4fa1..000000000
--- a/acinclude/ax_gcc_x86_cpu_supports.m4
+++ /dev/null
@@ -1,104 +0,0 @@
-# ============================================================================
-#  https://www.gnu.org/software/autoconf-archive/ax_gcc_x86_cpu_supports.html
-# ============================================================================
-#
-# SYNOPSIS
-#
-#   AX_GCC_X86_CPU_SUPPORTS(X86-INSTRUCTION-SET,
-#     [ACTION-IF-FOUND],[ACTION-IF-NOT-FOUND])
-#
-# DESCRIPTION
-#
-#   Checks if the host cpu supports X86-INSTRUCTION-SET. The instruction set
-#   that can be tested are "mmx, popcnt, sse, sse2, sse3, sse4.1, sse4.2,
-#   sse4a, avx, avx2, avx512f, fma, fma4, bmi, bmi2". If the instruction set
-#   is supported by the host cpu, the C preprocessor macro
-#   HAVE_XXX_INSTRUCTIONS is set to 1. The XXX is up-cased instruction case
-#   with dot replaced by underscore. For example, the test for "sse4.2"
-#   would export HAVE_SSE4_2_INSTRUCTIONS=1. This macro requires gcc
-#   extended builtin function "__builtin_cpu_init" and
-#   "__builtin_cpu_supports" to detect the cpu features. It will error out
-#   if the compiler doesn't has these builtins.
-#
-#   If the test for the instruction set succeeded, the hook ACTION-IF-FOUND
-#   would run. Otherwise the hook ACTION-IF-NOT-FOUND would run if
-#   specified.
-#
-#   See also AX_CHECK_X86_FEATURES, which checks all the possible
-#   instruction set and export the corresponding CFLAGS.
-#
-# LICENSE
-#
-#   Copyright (c) 2016 Felix Chern <idryman@gmail.com>
-#
-#   This program is free software; you can redistribute it and/or modify it
-#   under the terms of the GNU General Public License as published by the
-#   Free Software Foundation; either version 2 of the License, or (at your
-#   option) any later version.
-#
-#   This program is distributed in the hope that it will be useful, but
-#   WITHOUT ANY WARRANTY; without even the implied warranty of
-#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
-#   Public License for more details.
-#
-#   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <https://www.gnu.org/licenses/>.
-#
-#   As a special exception, the respective Autoconf Macro's copyright owner
-#   gives unlimited permission to copy, distribute and modify the configure
-#   scripts that are the output of Autoconf when processing the Macro. You
-#   need not follow the terms of the GNU General Public License when using
-#   or distributing such scripts, even though portions of the text of the
-#   Macro appear in them. The GNU General Public License (GPL) does govern
-#   all other use of the material that constitutes the Autoconf Macro.
-#
-#   This special exception to the GPL applies to versions of the Autoconf
-#   Macro released by the Autoconf Archive. When you make and distribute a
-#   modified version of the Autoconf Macro, you may extend this special
-#   exception to the GPL to apply to your modified version as well.
-
-#serial 3
-
-AC_DEFUN_ONCE([_AX_GCC_X86_CPU_INIT],
- [AC_LANG_PUSH([C])
-  AC_CACHE_CHECK([for gcc __builtin_cpu_init function],
-    [ax_cv_gcc_check_x86_cpu_init],
-    [AC_RUN_IFELSE(
-      [AC_LANG_PROGRAM([#include <stdlib.h>],
-        [__builtin_cpu_init ();])
-      ],
-      [ax_cv_gcc_check_x86_cpu_init=yes],
-      [ax_cv_gcc_check_x86_cpu_init=no])])
-  AS_IF([test "X$ax_cv_gcc_check_x86_cpu_init" = "Xno"],
-    [AC_MSG_ERROR([Need GCC to support X86 CPU features tests])])
-])
-
-AC_DEFUN([AX_GCC_X86_CPU_SUPPORTS],
-  [AC_REQUIRE([AC_PROG_CC])
-   AC_REQUIRE([_AX_GCC_X86_CPU_INIT])
-   AC_LANG_PUSH([C])
-   AS_VAR_PUSHDEF([gcc_x86_feature], [AS_TR_SH([ax_cv_gcc_x86_cpu_supports_$1])])
-   AC_CACHE_CHECK([for x86 $1 instruction support],
-     [gcc_x86_feature],
-     [AC_RUN_IFELSE(
-       [AC_LANG_PROGRAM( [#include <stdlib.h> ],
-       [ __builtin_cpu_init ();
-         if (__builtin_cpu_supports("$1"))
-           return 0;
-         return 1;
-        ])],
-        [gcc_x86_feature=yes],
-        [gcc_x86_feature=no]
-     )]
-   )
-   AC_LANG_POP([C])
-   AS_VAR_IF([gcc_x86_feature],[yes],
-         [AC_DEFINE(
-           AS_TR_CPP([HAVE_$1_INSTRUCTIONS]),
-           [1],
-           [Define if $1 instructions are supported])
-          $2],
-          [$3]
-         )
-   AS_VAR_POPDEF([gcc_x86_feature])
-])
diff --git a/conda/faiss-gpu/build.sh b/conda/faiss-gpu/build.sh
index b0da4d8c5..25326c90d 100644
--- a/conda/faiss-gpu/build.sh
+++ b/conda/faiss-gpu/build.sh
@@ -1,5 +1,16 @@
+# Build avx2 version
+CXXFLAGS="-mavx2 -mf16c" ./configure --with-cuda=$CUDA_ROOT --with-cuda-arch="$CUDA_ARCH"
+make -j $CPU_COUNT
+make -C python _swigfaiss_avx2.so
+make clean
+
+# Build vanilla version (no avx)
 ./configure --with-cuda=$CUDA_ROOT --with-cuda-arch="$CUDA_ARCH"
 make -j $CPU_COUNT
+make -C python _swigfaiss.so
+
+make -C python build
+
 cd python
-make
+
 $PYTHON setup.py install --single-version-externally-managed --record=record.txt
diff --git a/conda/faiss-gpu/conda_build_config.yaml b/conda/faiss-gpu/conda_build_config.yaml
index 0c9ab8900..da98e5d41 100644
--- a/conda/faiss-gpu/conda_build_config.yaml
+++ b/conda/faiss-gpu/conda_build_config.yaml
@@ -5,7 +5,7 @@ cudatoolkit:
   - 9.0
   - 9.2
   - 10.0
-#  - 10.1 # cudatoolkit 10.1 packages are not yet available on Anaconda.
+  - 10.1
 pin_run_as_build:
   cudatoolkit:
     max_pin: x.x
diff --git a/conda/faiss/build.sh b/conda/faiss/build.sh
index 66ca439af..87ccb4cad 100644
--- a/conda/faiss/build.sh
+++ b/conda/faiss/build.sh
@@ -1,5 +1,16 @@
+# Build avx2 version
+CXXFLAGS="-mavx2 -mf16c" ./configure --without-cuda
+make -j $CPU_COUNT
+make -C python _swigfaiss_avx2.so
+make clean
+
+# Build vanilla version (no avx)
 ./configure --without-cuda
 make -j $CPU_COUNT
+make -C python _swigfaiss.so
+
+make -C python build
+
 cd python
-make
+
 $PYTHON setup.py install --single-version-externally-managed --record=record.txt
diff --git a/configure b/configure
index d5968a501..ed40daefd 100755
--- a/configure
+++ b/configure
@@ -2065,48 +2065,6 @@ $as_echo "$ac_res" >&6; }
   eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
 
 } # ac_fn_cxx_check_func
-
-# ac_fn_c_try_run LINENO
-# ----------------------
-# Try to link conftest.$ac_ext, and return whether this succeeded. Assumes
-# that executables *can* be run.
-ac_fn_c_try_run ()
-{
-  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
-  if { { ac_try="$ac_link"
-case "(($ac_try" in
-  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
-  *) ac_try_echo=$ac_try;;
-esac
-eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
-  (eval "$ac_link") 2>&5
-  ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
-  test $ac_status = 0; } && { ac_try='./conftest$ac_exeext'
-  { { case "(($ac_try" in
-  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
-  *) ac_try_echo=$ac_try;;
-esac
-eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
-  (eval "$ac_try") 2>&5
-  ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
-  test $ac_status = 0; }; }; then :
-  ac_retval=0
-else
-  $as_echo "$as_me: program exited with status $ac_status" >&5
-       $as_echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-       ac_retval=$ac_status
-fi
-  rm -rf conftest.dSYM conftest_ipa8_conftest.oo
-  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
-  as_fn_set_status $ac_retval
-
-} # ac_fn_c_try_run
 cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
@@ -6849,136 +6807,25 @@ test -n "$target_alias" &&
     NONENONEs,x,x, &&
   program_prefix=${target_alias}-
 
-ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-
-  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for gcc __builtin_cpu_init function" >&5
-$as_echo_n "checking for gcc __builtin_cpu_init function... " >&6; }
-if ${ax_cv_gcc_check_x86_cpu_init+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test "$cross_compiling" = yes; then :
-  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
-as_fn_error $? "cannot run test program while cross compiling
-See \`config.log' for more details" "$LINENO" 5; }
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <stdlib.h>
-int
-main ()
-{
-__builtin_cpu_init ();
-  ;
-  return 0;
-}
-
-_ACEOF
-if ac_fn_c_try_run "$LINENO"; then :
-  ax_cv_gcc_check_x86_cpu_init=yes
-else
-  ax_cv_gcc_check_x86_cpu_init=no
-fi
-rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
-  conftest.$ac_objext conftest.beam conftest.$ac_ext
-fi
-
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_gcc_check_x86_cpu_init" >&5
-$as_echo "$ax_cv_gcc_check_x86_cpu_init" >&6; }
-  if test "X$ax_cv_gcc_check_x86_cpu_init" = "Xno"; then :
-  as_fn_error $? "Need GCC to support X86 CPU features tests" "$LINENO" 5
-fi
-
-
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for cpu arch" >&5
 $as_echo_n "checking for cpu arch... " >&6; }
 
 
-case $target in
-  amd64-* | x86_64-*)
-    ARCH_CPUFLAGS="-mpopcnt"
-    ARCH_CXXFLAGS="-m64"
 
+  case $target in
+    amd64-* | x86_64-*)
+      ARCH_CPUFLAGS="-mpopcnt -msse4"
+      ARCH_CXXFLAGS="-m64"
+      ;;
+    aarch64*-*)
+      ARCH_CPUFLAGS="-march=armv8.2-a"
+      ;;
+    *) ;;
+  esac
 
-
-   ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-
-
-   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for x86 avx2 instruction support" >&5
-$as_echo_n "checking for x86 avx2 instruction support... " >&6; }
-if ${ax_cv_gcc_x86_cpu_supports_avx2+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test "$cross_compiling" = yes; then :
-  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
-as_fn_error $? "cannot run test program while cross compiling
-See \`config.log' for more details" "$LINENO" 5; }
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <stdlib.h>
-int
-main ()
-{
- __builtin_cpu_init ();
-         if (__builtin_cpu_supports("avx2"))
-           return 0;
-         return 1;
-
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_run "$LINENO"; then :
-  ax_cv_gcc_x86_cpu_supports_avx2=yes
-else
-  ax_cv_gcc_x86_cpu_supports_avx2=no
-
-fi
-rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
-  conftest.$ac_objext conftest.beam conftest.$ac_ext
-fi
-
-
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_gcc_x86_cpu_supports_avx2" >&5
-$as_echo "$ax_cv_gcc_x86_cpu_supports_avx2" >&6; }
-   ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-
-   if test "x$ax_cv_gcc_x86_cpu_supports_avx2" = xyes; then :
-
-$as_echo "#define HAVE_AVX2_INSTRUCTIONS 1" >>confdefs.h
-
-          ARCH_CPUFLAGS+=" -mavx2 -mf16c"
-else
-  ARCH_CPUFLAGS+=" -msse4"
-
-fi
-
-
-    ;;
-  aarch64*-*)
-    ARCH_CPUFLAGS="-march=armv8.2-a"
-    ;;
-  *) ;;
-esac
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $target CPUFLAGS+=$ARCH_CPUFLAGS CXXFLAGS+=$ARCH_CXXFLAGS" >&5
-$as_echo "$target CPUFLAGS+=$ARCH_CPUFLAGS CXXFLAGS+=$ARCH_CXXFLAGS" >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $target CPUFLAGS+=\"$ARCH_CPUFLAGS\" CXXFLAGS+=\"$ARCH_CXXFLAGS\"" >&5
+$as_echo "$target CPUFLAGS+=\"$ARCH_CPUFLAGS\" CXXFLAGS+=\"$ARCH_CXXFLAGS\"" >&6; }
 
 
 
diff --git a/makefile.inc.in b/makefile.inc.in
index bc46e879b..19d8511cd 100644
--- a/makefile.inc.in
+++ b/makefile.inc.in
@@ -8,7 +8,7 @@ CXXCPP       = @CXXCPP@
 CPPFLAGS     = -DFINTEGER=int @CPPFLAGS@ @OPENMP_CXXFLAGS@ @NVCC_CPPFLAGS@
 CXXFLAGS     = -fPIC @ARCH_CXXFLAGS@ -Wno-sign-compare @CXXFLAGS@
 CPUFLAGS     = @ARCH_CPUFLAGS@
-LDFLAGS      = @OPENMP_CXXFLAGS@ @LDFLAGS@ @NVCC_LDFLAGS@
+LDFLAGS      = @OPENMP_LDFLAGS@ @LDFLAGS@ @NVCC_LDFLAGS@
 LIBS         = @BLAS_LIBS@ @LAPACK_LIBS@ @LIBS@ @NVCC_LIBS@
 PYTHONCFLAGS = @PYTHON_CFLAGS@ -I@NUMPY_INCLUDE@
 SWIGFLAGS    = -DSWIGWORDSIZE64
diff --git a/python/Makefile b/python/Makefile
index 28fed702c..283656825 100644
--- a/python/Makefile
+++ b/python/Makefile
@@ -15,12 +15,15 @@ all: build
 swigfaiss.cpp: swigfaiss.swig ../libfaiss.a
 	$(SWIG) -python -c++ -Doverride= -I../ $(SWIGFLAGS) -o $@ $<
 
-swigfaiss.o: swigfaiss.cpp
+swigfaiss_avx2.cpp: swigfaiss.swig ../libfaiss.a
+	$(SWIG) -python -c++ -Doverride= -module swigfaiss_avx2 -I../ $(SWIGFLAGS) -o $@ $<
+
+%.o: %.cpp
 	$(CXX) $(CPPFLAGS) $(CXXFLAGS) $(CPUFLAGS) $(PYTHONCFLAGS) \
                -I../ -c $< -o $@
 
 # Extension is .so even on OSX.
-_swigfaiss.so: swigfaiss.o ../libfaiss.a
+_%.so: %.o ../libfaiss.a
 	$(CXX) $(SHAREDFLAGS) $(LDFLAGS) -o $@ $^ $(LIBS)
 
 build: _swigfaiss.so faiss.py
@@ -30,8 +33,7 @@ install: build
 	$(PYTHON) setup.py install
 
 clean:
-	rm -f swigfaiss.cpp swigfaiss.o swigfaiss.py
-	rm -f _swigfaiss.so
+	rm -f swigfaiss*.cpp swigfaiss*.o swigfaiss*.py _swigfaiss*.so
 	rm -rf build/
 
 .PHONY: all build clean install
diff --git a/python/faiss.py b/python/faiss.py
index fe0f2ee16..3adbbf4a8 100644
--- a/python/faiss.py
+++ b/python/faiss.py
@@ -8,14 +8,44 @@
 # not linting this file because it imports * form swigfaiss, which
 # causes a ton of useless warnings.
 
+from __future__ import print_function
+
 import numpy as np
 import sys
 import inspect
 import pdb
+import platform
+import subprocess
 
 
-# we import * so that the symbol X can be accessed as faiss.X
-from .swigfaiss import *
+def instruction_set():
+    if platform.system() == "Darwin":
+        if subprocess.check_output(["/usr/sbin/sysctl", "hw.optional.avx2_0"])[-1] == '1':
+            return "AVX2"
+        else:
+            return "default"
+    elif platform.system() == "Linux":
+        import numpy.distutils.cpuinfo
+        if "avx2" in numpy.distutils.cpuinfo.cpu.info[0]['flags']:
+            return "AVX2"
+        else:
+            return "default"
+
+
+try:
+    instr_set = instruction_set()
+    if instr_set == "AVX2":
+        print("Loading faiss with AVX2 support.", file=sys.stderr)
+        from .swigfaiss_avx2 import *
+    else:
+        print("Loading faiss.", file=sys.stderr)
+        from .swigfaiss import *
+
+except ImportError:
+    # we import * so that the symbol X can be accessed as faiss.X
+    print("Loading faiss.", file=sys.stderr)
+    from .swigfaiss import *
+
 
 __version__ = "%d.%d.%d" % (FAISS_VERSION_MAJOR,
                             FAISS_VERSION_MINOR,
diff --git a/python/setup.py b/python/setup.py
index cd92fb133..854d01a14 100644
--- a/python/setup.py
+++ b/python/setup.py
@@ -16,6 +16,11 @@ os.mkdir("faiss")
 shutil.copyfile("faiss.py", "faiss/__init__.py")
 shutil.copyfile("swigfaiss.py", "faiss/swigfaiss.py")
 shutil.copyfile("_swigfaiss.so", "faiss/_swigfaiss.so")
+try:
+    shutil.copyfile("swigfaiss_avx2.py", "faiss/swigfaiss_avx2.py")
+    shutil.copyfile("_swigfaiss_avx2.so", "faiss/_swigfaiss_avx2.so")
+except:
+    pass
 
 long_description="""
 Faiss is a library for efficient similarity search and clustering of dense