hello_tf.go

package main

import (
	"fmt"

	tf "github.com/tensorflow/tensorflow/tensorflow/go"
	"github.com/tensorflow/tensorflow/tensorflow/go/op"
)

func main() {
	// Construct an empty graph 
	s := op.NewScope()
	//Associates a new string constant with the graph s and the output is allocated to c
	c := op.Const(s, "Hello from TensorFlow version "+tf.Version())
	//builds and finalizes the graph rendering s unusable
	graph, err := s.Finalize()
	if err != nil {
		panic(err)
	}

	// Sets up a session using the graph
	/*
	https://danijar.com/what-is-a-tensorflow-session/
	A graph defines the computation. 
	It doesn’t compute anything, it doesn’t hold any values, it just defines the operations that you specified in your code.
	
	A session allows to execute graphs or part of graphs. 
	It allocates resources (on one or more machines) for that and holds the actual values of intermediate results 
	and variables.
	*/
	sess, err := tf.NewSession(graph, nil)
	if err != nil {
		panic(err)
	}
	//https://godoc.org/github.com/tensorflow/tensorflow/tensorflow/go#Session.Run
	//input, fetches and lastly targets which are computed and not returned
	//output is the fetches specified. if nil then it's empty
	output, err := sess.Run(nil, []tf.Output{c}, nil)
	if err != nil {
		panic(err)
	}
	//As we said they are returned in order so this is the value of c
	fmt.Println(output[0].Value())
}