go: Add an example.

Add an example (that will appear in Go doc) for a real use of the Go TensorFlow
APIs - using a pre-defined image recognition model for inference.

While at it a couple of minor tweaks:
- NewSession now accepts 'nil' for options as the documentation says it does
- Convenience accessors for the Outputs of an Operation
- Ability to extract (possibly partial) shapes from an Output

Another step towards #10
Change: 134560938

1 files changed, 49 insertions, 1 deletions

diff --git a/tensorflow/go/operation.go b/tensorflow/go/operation.go
index 0f14ea1bef..59c5c2a2b0 100644
--- a/tensorflow/go/operation.go
+++ b/tensorflow/go/operation.go
@@ -17,7 +17,11 @@ package tensorflow
 // #include <stdlib.h>
 // #include "tensorflow/c/c_api.h"
 import "C"
-import "unsafe"
+
+import (
+	"errors"
+	"unsafe"
+)
 
 // Operation that has been added to the graph.
 type Operation struct {
@@ -37,6 +41,18 @@ func (op *Operation) Type() string {
 	return C.GoString(C.TF_OperationOpType(op.c))
 }
 
+// NumOutputs returns the number of outputs of op.
+func (op *Operation) NumOutputs() int {
+	return int(C.TF_OperationNumOutputs(op.c))
+}
+
+// Output returns the i-th output of op.
+//
+// REQUIRES: 0 <= i < op.NumOutputs()
+func (op *Operation) Output(i int) Output {
+	return Output{op, i}
+}
+
 // Output represents one of the outputs of an operation in the graph. Has a
 // DataType (and eventually a Shape).  May be passed as an input argument to a
 // function for adding operations to a graph, or to a Session's Run() method to
@@ -49,6 +65,38 @@ type Output struct {
 	Index int
 }
 
+// Shape returns the (possibly incomplete) shape of the tensor produced p.
+//
+// Returns a slice of length 0 if the tensor is a scalar.  Returns a slice
+// where shape[i] is the size of the i-th dimension of the tensor, or -1 if the
+// size of that dimension is not known.
+//
+// Returns an error if the number of dimensions of the tensor is not known.
+func (p Output) Shape() (shape []int64, err error) {
+	status := newStatus()
+	port := p.c()
+	ndims := C.TF_GraphGetTensorNumDims(p.Op.g.c, port, status.c)
+	if err := status.Err(); err != nil {
+		return nil, err
+	}
+	if ndims < 0 {
+		return nil, errors.New("unknown number of dimensions")
+	}
+	if ndims == 0 {
+		return nil, nil
+	}
+	dims := make([]C.int64_t, ndims)
+	C.TF_GraphGetTensorShape(p.Op.g.c, port, &dims[0], ndims, status.c)
+	if err := status.Err(); err != nil {
+		return nil, err
+	}
+	ret := make([]int64, ndims)
+	for i := 0; i < int(ndims); i++ {
+		ret[i] = int64(dims[i])
+	}
+	return ret, nil
+}
+
 func (p *Output) c() C.TF_Port {
 	return C.TF_Port{oper: p.Op.c, index: C.int(p.Index)}
 }