From 0c25f4b5c83683f1981ff761ead6a826e07a9700 Mon Sep 17 00:00:00 2001
From: Jon Malmaud <malmaud@gmail.com>
Date: Tue, 24 Oct 2017 01:23:55 -0400
Subject: [PATCH 1/3] Define 'close(::Session)'

---
 src/core.jl  | 18 ++++++++++++++++--
 src/run.jl   | 13 ++++++++++++-
 test/core.jl |  9 +++++++++
 3 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/src/core.jl b/src/core.jl
index 76e9b9a1..fc76699e 100644
--- a/src/core.jl
+++ b/src/core.jl
@@ -554,8 +554,7 @@ mutable struct Session
         this = new(ptr, graph)
         check_status(status)
         finalizer(this, self->begin
-            status = Status()
-            @tfcall(:TF_DeleteSession, Void, (Ptr{Void}, Ptr{Void}), self.ptr, status.ptr)
+            close(self)
         end)
         return this
     end
@@ -571,6 +570,21 @@ mutable struct Session
     end
 end
 
+"""
+    `close(sess::Session)`
+
+Closes the TensorFlow session, freeing the associated computational resources.
+"""
+function Base.close(sess::Session)
+    if sess.ptr != C_NULL
+        status = Status()
+        @tfcall(:TF_DeleteSession, Void, (Ptr{Void}, Ptr{Void}), sess.ptr, status.ptr)
+        check_status(status)
+        sess.ptr = C_NULL
+    end
+    return nothing
+end
+
 
 mutable struct Buffer
     ptr::Ptr{Void}
diff --git a/src/run.jl b/src/run.jl
index c82f56b3..233d8718 100644
--- a/src/run.jl
+++ b/src/run.jl
@@ -77,9 +77,18 @@ function build_input(tensor_map::Dict)
     input_tensors, input_values
 end
 
+struct ClosedSessionError <: Exception
+end
+
+function Base.show(io::IO, err::ClosedSessionError)
+    print(io, "Tried to call 'run' with a closed TensorFlow session.")
+end
+
 function run(sess::Session, inputs, input_values, outputs, targets)
     #Low level run, without size checking, and type conversion etc.
-
+    if sess.ptr == C_NULL
+        throw(ClosedSessionError())
+    end
     status = Status()
     output_values = fill(C_NULL, length(outputs))
     input_tensors = [RawTensor(x) for x in input_values]
@@ -184,6 +193,8 @@ end
 
 
 """
+    `run(sess::Session, output, input_dict::Dict)`
+
 Compute the result of one of more operations in the computation graph.
 """
 function run(sess::Session, output, input_dict)
diff --git a/test/core.jl b/test/core.jl
index 8bf438b8..ce885c93 100644
--- a/test/core.jl
+++ b/test/core.jl
@@ -26,6 +26,15 @@ end
     end
 end
 
+@testset "Session closing" begin
+    session = tf.Session(Graph())
+    x = constant(1)
+    @test run(session, x) == 1
+    close(session)
+    close(session)  # Test that we can safely call `close` twice on the same session
+    @test_throws tf.ClosedSessionError run(session, x)
+end
+
 @testset "get_operations" begin
     let
         graph = Graph()

From d33888b4fb71f2587a3e58d85dd3a4cfbb21ff56 Mon Sep 17 00:00:00 2001
From: Jon Malmaud <malmaud@gmail.com>
Date: Tue, 24 Oct 2017 01:28:28 -0400
Subject: [PATCH 2/3] Fix docstrings

---
 src/core.jl | 2 +-
 src/run.jl  | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/core.jl b/src/core.jl
index fc76699e..8a1de9db 100644
--- a/src/core.jl
+++ b/src/core.jl
@@ -571,7 +571,7 @@ mutable struct Session
 end
 
 """
-    `close(sess::Session)`
+    close(sess::Session)
 
 Closes the TensorFlow session, freeing the associated computational resources.
 """
diff --git a/src/run.jl b/src/run.jl
index 233d8718..51a7efe5 100644
--- a/src/run.jl
+++ b/src/run.jl
@@ -193,7 +193,8 @@ end
 
 
 """
-    `run(sess::Session, output, input_dict::Dict)`
+    run(sess::Session, output, input_dict::Dict)
+
 
 Compute the result of one of more operations in the computation graph.
 """

From f25ea1ee1fb985ba967e226720c4d3a4ff578d43 Mon Sep 17 00:00:00 2001
From: Jon Malmaud <malmaud@gmail.com>
Date: Tue, 24 Oct 2017 15:45:36 -0400
Subject: [PATCH 3/3] Revise error message

---
 src/run.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/run.jl b/src/run.jl
index 51a7efe5..6d679367 100644
--- a/src/run.jl
+++ b/src/run.jl
@@ -81,7 +81,7 @@ struct ClosedSessionError <: Exception
 end
 
 function Base.show(io::IO, err::ClosedSessionError)
-    print(io, "Tried to call 'run' with a closed TensorFlow session.")
+    print(io, "An operation was attempted on a closed TensorFlow session.")
 end
 
 function run(sess::Session, inputs, input_values, outputs, targets)