diff --git a/configure.ac b/configure.ac
index 1098203b..e111398b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,7 +1,7 @@
 AC_REVISION([m4_esyscmd_s([git describe --always])])
 
 AC_PREREQ(2.63)
-AC_INIT([musrfit],[0.18.0],[andreas.suter@psi.ch])
+AC_INIT([musrfit],[1.0.0],[andreas.suter@psi.ch])
 AC_CONFIG_AUX_DIR(admin)
 AC_CANONICAL_HOST
 #AC_MSG_RESULT([${host} ${host_cpu} ${host_vendor} ${host_os}])
@@ -34,8 +34,8 @@ dnl -----------------------------------------------
 
 
 #release versioning
-MUSR_MAJOR_VERSION=0
-MUSR_MINOR_VERSION=18
+MUSR_MAJOR_VERSION=1
+MUSR_MINOR_VERSION=0
 MUSR_MICRO_VERSION=0
 
 #release versioning
@@ -875,8 +875,7 @@ AC_ARG_ENABLE([dks], [AS_HELP_STRING([--enable-dks],[build musrfit with DKS (GPU
    DKS_CFLAGS=""
 
    dnl ---------------------------------------------
-   dnl Check (i) that Cuda is found. (ii) that DKS is found
-   dnl Eventually also openCL only should be tested, i.e. DKS without Cuda
+   dnl Check (i) that Cuda is found, if not check OpenCL. (ii) that DKS is found
    dnl This could also mean openCL without GPU, e.g. on Mac OS X
    dnl ---------------------------------------------
 
@@ -902,22 +901,59 @@ AC_ARG_ENABLE([dks], [AS_HELP_STRING([--enable-dks],[build musrfit with DKS (GPU
    if test -x "$cuda_prefix/bin/nvcc"; then
      AC_MSG_RESULT([found])
      AC_DEFINE_UNQUOTED([NVCC_PATH], ["$cuda_prefix/bin/nvcc"], [path to nvcc binary])
+     CUDA_FOUND="true"
+     CUDA_CFLAGS="-I$cuda_prefix/include"
+     CXXFLAGS="$CUDA_CFLAGS $CXXFLAGS"
+     CUDA_LDFLAGS="-L$cuda_prefix/lib64"
+     LDFLAGS="$CUDA_LDFLAGS $LDFLAGS"
    else
      AC_MSG_RESULT([not found!])
-     AC_MSG_FAILURE([nvcc was not found in $cuda_prefix/bin])
+     AC_MSG_WARN([nvcc was not found in $cuda_prefix/bin])
    fi
 
-   CUDA_CFLAGS="-I$cuda_prefix/include"
-   CXXFLAGS="$CUDA_CFLAGS $CXXFLAGS"
-   CUDA_LDFLAGS="-L$cuda_prefix/lib64"
-   LDFLAGS="$CUDA_LDFLAGS $LDFLAGS"
+   dnl if cuda has been found check the header and the lib
+   if test "$CUDA_FOUND" == "yes"; then
+     AC_CHECK_HEADER([cuda.h], [], AC_MSG_FAILURE([Couldn't find cuda.h]), [#include <cuda.h>])
+     AC_CHECK_LIB([cuda], [cuInit], [], AC_MSG_FAILURE([Couldn't find libcuda]))
+   fi
 
-   dnl And the header and the lib
-   AC_CHECK_HEADER([cuda.h], [], AC_MSG_FAILURE([Couldn't find cuda.h]), [#include <cuda.h>])
-   AC_CHECK_LIB([cuda], [cuInit], [], AC_MSG_FAILURE([Couldn't find libcuda]))
+   dnl ---------------------------------------------
+   dnl check for openCL in case CUDA is not found 
+   dnl ---------------------------------------------
+   AC_ARG_WITH([opencl], 
+               [AS_HELP_STRING([--with-opencl],[prefix of the OpenCL installation, e.g. /opt/AMDAPPSDK-3.0/])], 
+               [opencl_prefix=$withval],
+               [opencl_prefix="/opt/AMDAPPSDK-3.0"])
+
+   if test ! "$CUDA_FOUND" == "yes"; then
+     AC_MSG_NOTICE([CUDA not found, will try to find OpenCL])
+     AC_MSG_CHECKING([whether OpenCL is installed in a standard location])
+     if test "$opencl_prefix" == "yes"; then
+       if test "$withval" == "yes"; then
+         opencl_prefix="/opt/AMDAPPSDK-3.0"
+       fi
+     fi
+     AC_MSG_RESULT([${opencl_prefix}])
+
+     dnl Checking for opencl.h and libOpenCL.so
+     if test ! "$ARCH" = "DARWIN"; then 
+       AC_MSG_NOTICE([linux like system])
+       if test -x "$opencl_prefix/include/CL/opencl.h"; then
+         OPENCL_CFLAGS="-I$opencl_prefix/include/"
+         CXXFLAGS="$OPENCL_CFLAGS $CXXFLAGS"
+         OPENCL_LDFLAGS="-L$opencl_prefix/lib/x86_64/"
+         LDFLAGS="$OPENCL_LDFLAGS $LDFLAGS" 
+       else 
+         AC_MSG_RESULT([not found!])
+         AC_MSG_FAILURE([neither CUDA nor OpenCL found])
+       fi
+     else 
+       AC_MSG_NOTICE([Apple macOS system, not yet implemented])
+     fi
+   fi 
 
    dnl -------------------------------------------
-   dnl check for DKS
+   dnl check for DKSlibOpenCL.so 
    dnl -------------------------------------------
    AC_ARG_WITH([dks], 
                [AS_HELP_STRING([--with-dks],[prefix of the DKS installation, e.g. /usr/local/DKS/build])], 
@@ -940,12 +976,18 @@ AC_ARG_ENABLE([dks], [AS_HELP_STRING([--enable-dks],[build musrfit with DKS (GPU
    fi
 
    AC_DEFINE([HAVE_DKS], [1], [Define to 1 if DKS is available])
-dnl  AC_DEFINE([DKS_CUDA], [1], [Define to 1 if DKS Cuda is available])
-   DKS_CUDADIR="$cuda_prefix"
    DKS_INCDIR="$dks_prefix/include"
-   DKS_CFLAGS="-DDKS_OPENCL -DDKS_CUDA -I${DKS_INCDIR} ${CUDA_CFLAGS}"
    DKS_LIBDIR="$dks_prefix/lib"
-   DKS_LIBS="${CUDA_LDFLAGS} -lOpenCL -L${DKS_LIBDIR} -ldksshared"
+   if test "$CUDA_FOUND" == "yes"; then
+     DKS_CUDADIR="$cuda_prefix"
+     DKS_CFLAGS="-DDKS_OPENCL -DDKS_CUDA -I${DKS_INCDIR} ${CUDA_CFLAGS}"
+     DKS_LIBS="${CUDA_LDFLAGS} -lOpenCL -L${DKS_LIBDIR} -ldksshared"
+   else 
+     DKS_OPENCLDIR="$opencl_prefix"
+     DKS_CFLAGS="-DDKS_OPENCL -I${DKS_INCDIR} ${OPENCL_CFLAGS}"
+     DKS_LIBS="${OPENCL_LDFLAGS} -lOpenCL -L${DKS_LIBDIR} -ldksshared"
+   fi
+
    AC_SUBST(DKS_CFLAGS)
    AC_SUBST(DKS_LIBS)
 
@@ -1452,7 +1494,7 @@ else
 fi
 echo ""
 if test "${DKS_ENABLED}" = "1"; then
-  echo "   DKS enabled"
+  echo "   DKS enabled and found at ${dks_prefix}"
 else
   echo "   DKS disabled"
 fi