diff --git a/README.md b/README.md
index bcc1db5..0d0b105 100644
--- a/README.md
+++ b/README.md
@@ -6,9 +6,9 @@
 * **Bug reports**: https://github.com/wrathematics/argon2/issues
 
 
-**argon2** is an R package for secure password hashing via the argon2 algorithm.  It is a relatively new hashing algorithm and is believed to be very secure.  The package also includes some utilities that should be useful for digest authentication, including a wrapper of blake2b.  For similar R packages, see **sodium** and **bcrypt**.
+**argon2** is an R package for secure password hashing via the argon2 algorithm. It is a relatively new hashing algorithm and is believed to be very secure. The package also includes some utilities that should be useful for digest authentication, including a wrapper of blake2b. For similar R packages, see **sodium** and **bcrypt**.
 
-The package includes a source distribution of the latest implementation from the argon2 developers: https://github.com/P-H-C/phc-winner-argon2.  Note that we are unaffiliated with their project; if we break something, don't blame them!
+The package includes a source distribution of the latest implementation from the argon2 developers: https://github.com/P-H-C/phc-winner-argon2. Note that we are unaffiliated with their project; if we break something, don't blame them!
 
 
 
@@ -26,6 +26,8 @@ The development version is maintained on GitHub:
 remotes::install_github("wrathematics/argon2")
 ```
 
+If you build the package from source, you can enable CPU vectorization optimizations by using the configure flag `--enable-vec`. This improvement can not be made the default because of CRAN rules which I disagree with.
+
 
 
 ## Usage
diff --git a/configure b/configure
index c0406e1..b5f6255 100755
--- a/configure
+++ b/configure
@@ -584,6 +584,7 @@ PACKAGE_URL=
 ac_unique_file="DESCRIPTION"
 ac_subst_vars='LTLIBOBJS
 LIBOBJS
+ADDL_CFLAGS
 FILL_IMPL
 OBJEXT
 EXEEXT
@@ -634,6 +635,7 @@ SHELL'
 ac_subst_files=''
 ac_user_opts='
 enable_option_checking
+enable_vec
 '
       ac_precious_vars='build_alias
 host_alias
@@ -1257,6 +1259,12 @@ if test -n "$ac_init_help"; then
 
   cat <<\_ACEOF
 
+Optional Features:
+  --disable-option-checking  ignore unrecognized --enable/--with options
+  --disable-FEATURE       do not include FEATURE (same as --enable-FEATURE=no)
+  --enable-FEATURE[=ARG]  include FEATURE [ARG=yes]
+  --enable-vec            Enable vectorized optimizations.
+
 Some influential environment variables:
   CC          C compiler command
   CFLAGS      C compiler flags
@@ -1844,22 +1852,33 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 
-# Get C compiler from R
-: ${R_HOME=`R RHOME`}
-if test -z "${R_HOME}"; then
-  echo "could not determine R_HOME"
-  exit 1
+
+# Check whether --enable-vec was given.
+if test "${enable_vec+set}" = set; then :
+  enableval=$enable_vec; USE_VEC="yes"
+else
+  USE_VEC="no"
+
 fi
-CC=`"${R_HOME}/bin/R" CMD config CC`
 
 
-ac_ext=c
+
+if test "X${USE_VEC}" = "Xyes"; then
+  # Get C compiler from R
+  : ${R_HOME=`R RHOME`}
+  if test -z "${R_HOME}"; then
+    echo "could not determine R_HOME"
+    exit 1
+  fi
+  CC=`"${R_HOME}/bin/R" CMD config CC`
+
+  ac_ext=c
 ac_cpp='$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
 
-ac_ext=c
+  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'
@@ -2684,14 +2703,14 @@ 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$ax_cv_gcc_check_x86_cpu_init" = "Xno"; then :
+  if test "X$ax_cv_gcc_check_x86_cpu_init" = "Xno"; then :
   CC_IS_GCC="no"
 else
   CC_IS_GCC="yes"
 fi
 
-if test "X${CC_IS_GCC}" = "Xyes"; then
-  ac_ext=c
+  if test "X${CC_IS_GCC}" = "Xyes"; then
+    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'
@@ -2738,72 +2757,6 @@ fi
 
 
 
-   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 avx512f instruction support" >&5
-$as_echo_n "checking for x86 avx512f instruction support... " >&6; }
-if ${ax_cv_gcc_x86_cpu_supports_avx512f+:} 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.$ac_ext
-/* end confdefs.h.  */
-#include <stdlib.h>
-int
-main ()
-{
- __builtin_cpu_init ();
-         if (__builtin_cpu_supports("avx512f"))
-           return 0;
-         return 1;
-
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_run "$LINENO"; then :
-  ax_cv_gcc_x86_cpu_supports_avx512f=yes
-else
-  ax_cv_gcc_x86_cpu_supports_avx512f=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: $ax_cv_gcc_x86_cpu_supports_avx512f" >&5
-$as_echo "$ax_cv_gcc_x86_cpu_supports_avx512f" >&6; }
-   ac_ext=c
-ac_cpp='$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$ax_cv_gcc_x86_cpu_supports_avx512f" = xyes; then :
-
-$as_echo "#define HAVE_AVX512F_INSTRUCTIONS 1" >>confdefs.h
-
-          HAS_AVX512F="yes"
-else
-  HAS_AVX512F="no"
-
-fi
-
-
-
-
    ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
 ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
@@ -2935,28 +2888,42 @@ fi
 
 
 
-  if test "X${HAS_AVX512F}" = "Xno" -a "X${HAS_AVX2}" = "Xno" -a "X${HAS_SSE2}" = "Xno"; then
-    FILL_IMPL="ref.o"
+    if test "X${HAS_AVX2}" = "Xyes"; then
+      FILL_IMPL="opt.o"
+      ADDL_CFLAGS="-mavx2"
+    elif test "X${HAS_SSE2}" = "Xyes"; then
+      FILL_IMPL="opt.o"
+      ADDL_CFLAGS="-msse2"
+    else
+      FILL_IMPL="ref.o"
+      ADDL_CFLAGS=""
+    fi
   else
-    FILL_IMPL="opt.o"
+    HAS_AVX2="unknown - couldn't find gcc"
+    HAS_SSE2="unknown - couldn't find gcc"
+    ADDL_CFLAGS=""
+    FILL_IMPL="ref.o"
   fi
 else
-  HAS_AVX512F="unknown - couldn't find gcc"
-  HAS_AVX2="${HAS_AVX512F}"
-  HAS_SSE2="${HAS_AVX512F}"
+  HAS_AVX2="unknown - did not check"
+  HAS_SSE2="unknown - did not check"
+  ADDL_CFLAGS=""
   FILL_IMPL="ref.o"
 fi
 
+
+
 echo " "
 echo "****************** Results of argon2 package configure *******************"
 echo "* Arch Report"
-echo "*   >> AVX512f = ${HAS_AVX512F}"
 echo "*   >> AVX2 = ${HAS_AVX2}"
 echo "*   >> SSE2 = ${HAS_SSE2}"
+echo "*   >> CFLAGS += ${ADDL_CFLAGS}"
 echo "**************************************************************************"
 echo " "
 
 
+
 ac_config_files="$ac_config_files src/Makevars"
 
 cat >confcache <<\_ACEOF
diff --git a/configure.ac b/configure.ac
index 2e90bbf..9ac1b4e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3,40 +3,57 @@ AC_INIT
 AC_CONFIG_SRCDIR([DESCRIPTION])
 m4_include([tools/ax_gcc_x86_cpu_supports.m4])
 
-# Get C compiler from R
-: ${R_HOME=`R RHOME`}
-if test -z "${R_HOME}"; then
-  echo "could not determine R_HOME"
-  exit 1
-fi
-CC=`"${R_HOME}/bin/R" CMD config CC`
-
-
-AC_LANG_PUSH([C])
-AC_CACHE_CHECK([for ${CC} __builtin_cpu_init function],
-  [ax_cv_gcc_check_x86_cpu_init],
-  [AC_RUN_IFELSE(
-    [AC_LANG_PROGRAM([#include <stdlib.h>],
-      [__builtin_cpu_init ();])
-    ],
-    [ax_cv_gcc_check_x86_cpu_init=yes],
-    [ax_cv_gcc_check_x86_cpu_init=no])])
-AS_IF([test "X$ax_cv_gcc_check_x86_cpu_init" = "Xno"], [CC_IS_GCC="no"], [CC_IS_GCC="yes"])
-
-if test "X${CC_IS_GCC}" = "Xyes"; then
-  AX_GCC_X86_CPU_SUPPORTS(avx512f, [HAS_AVX512F="yes"],[HAS_AVX512F="no"])
-  AX_GCC_X86_CPU_SUPPORTS(avx2, [HAS_AVX2="yes"],[HAS_AVX2="no"])
-  AX_GCC_X86_CPU_SUPPORTS(sse2, [HAS_SSE2="yes"],[HAS_SSE2="no"])
+
+AC_ARG_ENABLE(vec,
+  AC_HELP_STRING([--enable-vec], [Enable vectorized optimizations.]),
+  [USE_VEC="yes"], [USE_VEC="no"]
+)
+
+
+if test "X${USE_VEC}" = "Xyes"; then
+  # Get C compiler from R
+  : ${R_HOME=`R RHOME`}
+  if test -z "${R_HOME}"; then
+    echo "could not determine R_HOME"
+    exit 1
+  fi
+  CC=`"${R_HOME}/bin/R" CMD config CC`
   
-  if test "X${HAS_AVX512F}" = "Xno" -a "X${HAS_AVX2}" = "Xno" -a "X${HAS_SSE2}" = "Xno"; then
-    FILL_IMPL="ref.o"
+  AC_LANG_PUSH([C])
+  AC_CACHE_CHECK([for ${CC} __builtin_cpu_init function],
+    [ax_cv_gcc_check_x86_cpu_init],
+    [AC_RUN_IFELSE(
+      [AC_LANG_PROGRAM([#include <stdlib.h>],
+        [__builtin_cpu_init ();])
+      ],
+      [ax_cv_gcc_check_x86_cpu_init=yes],
+      [ax_cv_gcc_check_x86_cpu_init=no])])
+  AS_IF([test "X$ax_cv_gcc_check_x86_cpu_init" = "Xno"], [CC_IS_GCC="no"], [CC_IS_GCC="yes"])
+  
+  if test "X${CC_IS_GCC}" = "Xyes"; then
+    AX_GCC_X86_CPU_SUPPORTS(avx2, [HAS_AVX2="yes"],[HAS_AVX2="no"])
+    AX_GCC_X86_CPU_SUPPORTS(sse2, [HAS_SSE2="yes"],[HAS_SSE2="no"])
+    
+    if test "X${HAS_AVX2}" = "Xyes"; then
+      FILL_IMPL="opt.o"
+      ADDL_CFLAGS="-mavx2"
+    elif test "X${HAS_SSE2}" = "Xyes"; then
+      FILL_IMPL="opt.o"
+      ADDL_CFLAGS="-msse2"
+    else
+      FILL_IMPL="ref.o"
+      ADDL_CFLAGS=""
+    fi
   else
-    FILL_IMPL="opt.o"
+    HAS_AVX2="unknown - couldn't find gcc"
+    HAS_SSE2="unknown - couldn't find gcc"
+    ADDL_CFLAGS=""
+    FILL_IMPL="ref.o"
   fi
 else
-  HAS_AVX512F="unknown - couldn't find gcc"
-  HAS_AVX2="${HAS_AVX512F}"
-  HAS_SSE2="${HAS_AVX512F}"
+  HAS_AVX2="unknown - did not check"
+  HAS_SSE2="unknown - did not check"
+  ADDL_CFLAGS=""
   FILL_IMPL="ref.o"
 fi
 
@@ -45,12 +62,13 @@ fi
 echo " "
 echo "****************** Results of argon2 package configure *******************"
 echo "* Arch Report"
-echo "*   >> AVX512f = ${HAS_AVX512F}"
 echo "*   >> AVX2 = ${HAS_AVX2}"
 echo "*   >> SSE2 = ${HAS_SSE2}"
+echo "*   >> CFLAGS += ${ADDL_CFLAGS}"
 echo "**************************************************************************"
 echo " "
 
 AC_SUBST(FILL_IMPL)
+AC_SUBST(ADDL_CFLAGS)
 AC_CONFIG_FILES([src/Makevars])
 AC_OUTPUT
diff --git a/src/Makevars.in b/src/Makevars.in
index 5fc1cef..6977512 100644
--- a/src/Makevars.in
+++ b/src/Makevars.in
@@ -1,4 +1,4 @@
-PKG_CFLAGS = $(SHLIB_OPENMP_CFLAGS) -I./argon2
+PKG_CFLAGS = $(SHLIB_OPENMP_CFLAGS) -I./argon2 @ADDL_CFLAGS@
 PKG_LIBS = $(SHLIB_OPENMP_CFLAGS)
 
 ARGON2_OBJS = \
@@ -17,11 +17,8 @@ R_OBJS = \
 	raw_as_char.o
 
 OBJECTS = $(ARGON2_OBJS) $(R_OBJS)
-
 all: $(SHLIB)
-
 $(SHLIB): $(OBJECTS) 
 
-
 clean:
 	rm -rf *.o *.so *.dll 
diff --git a/src/Makevars.win b/src/Makevars.win
index 26f93bc..ed955e9 100644
--- a/src/Makevars.win
+++ b/src/Makevars.win
@@ -17,11 +17,8 @@ R_OBJS = \
 	raw_as_char.o
 
 OBJECTS = $(ARGON2_OBJS) $(R_OBJS)
-
 all: $(SHLIB)
-
 $(SHLIB): $(OBJECTS) 
 
-
 clean:
 	rm -rf *.o *.so *.dll