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// Copyright 2016 The TensorFlow Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package tensorflow
// #include <stdlib.h>
// #include "tensorflow/c/c_api.h"
import "C"
import (
"errors"
"runtime"
"sync"
"unsafe"
)
// Session drives a TensorFlow graph computation.
//
// When a Session is created with a given target, a new Session object is bound
// to the universe of resources specified by that target. Those resources are
// available to this session to perform computation described in the GraphDef.
// After creating the session with a graph, the caller uses the Run() API to
// perform the computation and potentially fetch outputs as Tensors.
// A Session allows concurrent calls to Run().
type Session struct {
c *C.TF_Session
// For ensuring that:
// - Close() blocks on all Run() calls to complete.
// - Close() can be called multiple times.
wg sync.WaitGroup
mu sync.Mutex
}
// NewSession creates a new execution session with the associated graph.
// options may be nil to use the default options.
func NewSession(graph *Graph, options *SessionOptions) (*Session, error) {
status := newStatus()
cOpt := options.c()
cSess := C.TF_NewSession(graph.c, cOpt, status.c)
C.TF_DeleteSessionOptions(cOpt)
if err := status.Err(); err != nil {
return nil, err
}
s := &Session{c: cSess}
runtime.SetFinalizer(s, func(s *Session) { s.Close() })
return s, nil
}
// Run the graph with the associated session starting with the supplied inputs.
// inputs and outputs may be set to nil. Runs, but does not return Tensors
// for operations specified in targets.
//
// On success, returns the Tensor outputs in the same order as supplied in
// the outputs argument. If outputs is set to nil, the returned Tensor outputs
// is empty.
func (s *Session) Run(inputs map[Output]*Tensor, outputs []Output, targets []*Operation) ([]*Tensor, error) {
s.mu.Lock()
if s.c == nil {
s.mu.Unlock()
return nil, errors.New("session is closed")
}
s.wg.Add(1)
s.mu.Unlock()
defer s.wg.Done()
var inputPorts []C.TF_Output
var inputValues []*C.TF_Tensor
if inputs != nil {
for port, tensor := range inputs {
inputPorts = append(inputPorts, port.c())
inputValues = append(inputValues, tensor.c)
}
}
var outputPorts []C.TF_Output
for _, port := range outputs {
outputPorts = append(outputPorts, port.c())
}
outputValues := make([]*C.TF_Tensor, len(outputs))
var cTargets []*C.TF_Operation
for _, target := range targets {
cTargets = append(cTargets, target.c)
}
status := newStatus()
var inputPortsPtr *C.TF_Output
var inputValuesPtr **C.TF_Tensor
if len(inputPorts) > 0 {
inputPortsPtr = &inputPorts[0]
inputValuesPtr = &inputValues[0]
}
var outputPortsPtr *C.TF_Output
var outputValuesPtr **C.TF_Tensor
if len(outputPorts) > 0 {
outputPortsPtr = &outputPorts[0]
outputValuesPtr = &outputValues[0]
}
var cTargetsPtr **C.TF_Operation
if len(cTargets) > 0 {
cTargetsPtr = &cTargets[0]
}
C.TF_SessionRun(s.c, nil, inputPortsPtr, inputValuesPtr, C.int(len(inputPorts)), outputPortsPtr, outputValuesPtr, C.int(len(outputPorts)), cTargetsPtr, C.int(len(cTargets)), nil, status.c)
if err := status.Err(); err != nil {
return nil, err
}
tensors := make([]*Tensor, len(outputValues))
for i, val := range outputValues {
tensors[i] = newTensorFromC(val)
}
return tensors, nil
}
// Close a session. This contacts any other processes associated with this
// session, if applicable. Blocks until all previous calls to Run have returned.
func (s *Session) Close() error {
s.mu.Lock()
defer s.mu.Unlock()
s.wg.Wait()
if s.c == nil {
return nil
}
status := newStatus()
C.TF_CloseSession(s.c, status.c)
if err := status.Err(); err != nil {
return err
}
C.TF_DeleteSession(s.c, status.c)
s.c = nil
return status.Err()
}
// SessionOptions contains configuration information for a session.
type SessionOptions struct {
// Target indicates the TensorFlow runtime to connect to.
//
// If 'target' is empty or unspecified, the local TensorFlow runtime
// implementation will be used. Otherwise, the TensorFlow engine
// defined by 'target' will be used to perform all computations.
//
// "target" can be either a single entry or a comma separated list
// of entries. Each entry is a resolvable address of one of the
// following formats:
// local
// ip:port
// host:port
// ... other system-specific formats to identify tasks and jobs ...
//
// NOTE: at the moment 'local' maps to an in-process service-based
// runtime.
//
// Upon creation, a single session affines itself to one of the
// remote processes, with possible load balancing choices when the
// "target" resolves to a list of possible processes.
//
// If the session disconnects from the remote process during its
// lifetime, session calls may fail immediately.
Target string
}
// c converts the SessionOptions to the C API's TF_SessionOptions. Callers must
// deallocate by calling C.TF_DeleteSessionOptions().
func (o *SessionOptions) c() *C.TF_SessionOptions {
opt := C.TF_NewSessionOptions()
if o == nil {
return opt
}
t := C.CString(o.Target)
C.TF_SetTarget(opt, t)
C.free(unsafe.Pointer(t))
return opt
}
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