Merge pull request #470 from rstudio/as-tensor-generic

add S3 generic `as_tensor`

Author: t-kalinowski

NAMESPACE

@@ -45,6 +45,8 @@ S3method(as.matrix,tensorflow.python.ops.variables.Variable)
 S3method(as.numeric,python.builtin.EagerTensor)
 S3method(as.numeric,tensorflow.python.framework.ops.EagerTensor)
 S3method(as.numeric,tensorflow.python.ops.variables.Variable)
+S3method(as_tensor,default)
+S3method(as_tensor,double)
 S3method(asin,tensorflow.tensor)
 S3method(atan,tensorflow.tensor)
 S3method(ceiling,tensorflow.tensor)
@@ -74,6 +76,7 @@ S3method(tanpi,tensorflow.tensor)
 export("%as%")
 export(all_dims)
 export(array_reshape)
+export(as_tensor)
 export(dict)
 export(evaluate)
 export(export_savedmodel)

NEWS.md

@@ -1,5 +1,7 @@
 # tensorflow (development version)
 
+- Added S3 generic `as_tensor()`.
+
 # tensorflow 2.5.0
 
 - Updated default Tensorflow version to 2.5.

R/generics.R

@@ -336,3 +336,59 @@ switch_fun_if_tf <- function(x, y, version = "1.14") {
   else
     y
 }
+
+
+
+#' as_tensor
+#'
+#' Coerce objects to tensorflow tensors (potentially of a specific dtype). The
+#' provided default methods will call
+#' [`tf.convert_to_tensor`](https://www.tensorflow.org/api_docs/python/tf/convert_to_tensor)
+#' and [`tf.cast`](https://www.tensorflow.org/api_docs/python/tf/cast) as
+#' appropriate.
+#'
+#' @param x object to convert
+#' @param dtype `NULL`, a tensorflow dtype (`tf$int32`), or something coercible
+#'   to one (e.g. a string `"int32"`)
+#' @param ..., ignored
+#' @param name `NULL` or a string. Useful for debugging in graph mode, ignored
+#'   while in eager mode.
+#'
+#' @return a tensorflow tensor
+#'
+#' @export
+#'
+#' @examples
+#' \dontrun{
+#' as_tensor(42, "int32")
+#' as_tensor(as_tensor(42))
+#' }
+as_tensor <- function(x, dtype = NULL, ..., name = NULL) UseMethod("as_tensor")
+
+#' @rdname as_tensor
+#' @export
+as_tensor.default <- function(x, dtype = NULL, ..., name = NULL) {
+  x <- tf$convert_to_tensor(x, dtype_hint = dtype, name = name)
+  if (is.null(dtype))
+    x
+  else
+    tf$cast(x, dtype, name = name)
+}
+
+#' @rdname as_tensor
+#' @export
+as_tensor.double <- function(x, dtype = NULL, ..., name = NULL) {
+  if (!is.null(dtype)) {
+    dtype <- tf$as_dtype(dtype)
+    if (dtype$is_integer) {
+      # tf.cast() overflows quietly, at least R raises a warning (and produces NA)
+      if (dtype$max <= .Machine$integer.max)
+        storage.mode(x) <- "integer"
+
+      if (anyNA(x))
+        stop("converting R numerics with NA values to integer dtypes not supported")
+    }
+  }
+
+  NextMethod()
+}

man/as_tensor.Rd

@@ -31,8 +31,6 @@ arr <- function(..., mode = "double", gen = seq_len)
 set.seed(42)
 rarr <- function(...) arr(..., gen=runif)
 
-as_tensor <- function(...) tf$convert_to_tensor(...)
-
 expect_near <- function(..., tol = 1e-5) expect_equal(..., tolerance = tol)
 
 

tests/testthat/helper-utils.R

@@ -0,0 +1,38 @@
+test_that("as_tensor works", {
+
+  test_is_tensor <- function(x, dtype) {
+    expect_s3_class(x, "tensorflow.tensor")
+    if(is.character(dtype))
+      expect_true(x$dtype[[dtype]])
+    else if(!is.null(dtype))
+      expect_true(x$dtype == tf$as_dtype(dtype))
+  }
+
+  test_is_tensor(as_tensor(3), 'is_floating')
+  test_is_tensor(as_tensor(3L), tf$int32)
+  test_is_tensor(as_tensor("foo"), tf$string)
+  test_is_tensor(as_tensor(TRUE), tf$bool)
+  test_is_tensor(as_tensor(1+1i), 'is_complex')
+
+  test_is_tensor(as_tensor(3L, tf$int32)   , tf$int32)
+  test_is_tensor(as_tensor(3L, tf$int64)   , tf$int64)
+  test_is_tensor(as_tensor(3L, tf$float32) , tf$float32)
+  test_is_tensor(as_tensor(3L, tf$float64) , tf$float64)
+  test_is_tensor(as_tensor(3L, tf$int8)    , tf$int8)
+
+  test_is_tensor(as_tensor(3.0, tf$float32), tf$float32)
+  test_is_tensor(as_tensor(3.0, tf$float64), tf$float64)
+  test_is_tensor(as_tensor(3.0, tf$int32)  , tf$int32)
+  test_is_tensor(as_tensor(3.0, tf$int64)  , tf$int64)
+  test_is_tensor(as_tensor(3.0, tf$int8)   , tf$int8)
+
+  # currently scalars -> float32; arrays -> float64
+  test_is_tensor(as_tensor(arr(3))       , 'is_floating')
+  test_is_tensor(as_tensor(arr(3, 3))    , 'is_floating')
+  test_is_tensor(as_tensor(arr(3, 3, 3)) , 'is_floating')
+
+  x <- tf$constant(3)
+  test_is_tensor(as_tensor(x, tf$int32), tf$int32)
+  test_is_tensor(as_tensor(x, tf$int64), tf$int64)
+
+})