Also look at CUDA_ROOT environment variable

configure.ac

@@ -391,10 +391,10 @@ AC_DEFUN([STARPU_CHECK_CUDA],
 if test x$enable_cuda = xyes -o x$enable_cuda = xmaybe; then
     STARPU_CHECK_CUDA("$cuda_dir", "$cuda_include_dir", "$cuda_lib_dir")
     if test "$have_valid_cuda" = "no" ; then
-	STARPU_CHECK_CUDA("$CUDA_PATH", "$CUDA_INC_PATH", "$CUDA_LIB_PATH")
+	STARPU_CHECK_CUDA("$CUDA_ROOT", "$CUDA_PATH", "$CUDA_INC_PATH", "$CUDA_LIB_PATH")
     fi
     if test "$have_valid_cuda" = "no" ; then
-	for f in "/usr/local/cuda" "/c/cuda" "/cygdrive/c/cuda" "/opt/cuda" "$CUDA_PATH" "$CUDA_INC_PATH/.." "$CUDA_INSTALL_PATH" "$CUDA_TOOLKIT"; do
+	for f in "/usr/local/cuda" "/c/cuda" "/cygdrive/c/cuda" "/opt/cuda" "$CUDA_ROOT" "$CUDA_PATH" "$CUDA_INC_PATH/.." "$CUDA_INSTALL_PATH" "$CUDA_TOOLKIT"; do
 	    if test -n "$f" ; then
 		STARPU_CHECK_CUDA("$f", "no", "no")
 		if test "$have_valid_cuda" = "yes" ; then
@@ -664,7 +664,7 @@ AC_DEFUN([STARPU_LOOK_FOR_OPENCL],
     	if test "x$has_opencl_being_checked" != "xyes" ; then
     	    STARPU_CHECK_OPENCL("$opencl_dir", "$opencl_include_dir", "$opencl_lib_dir")
 	    if test "$have_valid_opencl" = "no" ; then
-            	for f in "/usr/local/cuda" "/c/cuda" "/cygdrive/c/cuda" "/opt/cuda" "$CUDA_PATH" "$CUDA_INC_PATH/.." "$CUDA_INSTALL_PATH" "$CUDA_TOOLKIT"; do
+            	for f in "/usr/local/cuda" "/c/cuda" "/cygdrive/c/cuda" "/opt/cuda" "$CUDA_ROOT" "$CUDA_PATH" "$CUDA_INC_PATH/.." "$CUDA_INSTALL_PATH" "$CUDA_TOOLKIT"; do
 		    if test -n "$f" ; then
     			STARPU_CHECK_OPENCL("$f", "no", "no")
 			if test "$have_valid_opencl" = "yes" ; then