switch to tf.keras as default implementation

Author: Sigrid Keydana

NEWS.md

@@ -1,4 +1,9 @@
 
+## Development version
+
+- Use `tf.keras` as default implementation module.
+
+
 ## Keras 2.2.4 (CRAN)
 
 - Improve handling of `timeseries_generator()` in calls to `fit_generator()`

R/package.R

@@ -77,6 +77,7 @@ use_backend <- function(backend = c("tensorflow", "cntk", "theano", "plaidml"))
   } else {
     Sys.setenv(KERAS_BACKEND = match.arg(backend))
   }
+  if (backend != "tensorflow") use_implementation("keras")
 }
 
 
@@ -87,6 +88,8 @@ keras <- NULL
 
   # resolve the implementaiton module (might be keras proper or might be tensorflow)
   implementation_module <- resolve_implementation_module()
+  if (implementation_module == "tensorflow.python.keras")
+    Sys.setenv(KERAS_IMPLEMENTATION = "tensorflow")
 
   # if KERAS_PYTHON is defined then forward it to RETICULATE_PYTHON
   keras_python <- get_keras_python()
@@ -160,7 +163,7 @@ resolve_implementation_module <- function() {
   implementation_module
 }
 
-get_keras_implementation <- function(default = "keras") {
+get_keras_implementation <- function(default = "tensorflow") {
   get_keras_option("KERAS_IMPLEMENTATION", default = default)
 }