feat(wrapper/tensor): complete draft of wrapper/tensor

wrapper/tensor.go

@@ -898,3 +898,47 @@ func NoGrad(fn interface{}) (retVal interface{}, err error) {
 
 	return retVal, nil
 }
+
+// NoGradGuard is a RAII guard that prevents gradient tracking until deallocated.
+type NoGradGuard struct {
+	enabled bool
+}
+
+// Disables gradient tracking, this will be enabled back when the
+// returned value gets deallocated.
+func (ngg NoGradGuard) NoGradGuard() NoGradGuard {
+	return NoGradGuard{enabled: MustGradSetEnabled(false)}
+}
+
+// Drop drops the NoGradGuard state.
+func (ngg NoGradGuard) Drop() {
+	MustGradSetEnabled(ngg.enabled)
+}
+
+// Reduction type is an enum-like type
+type Reduction int
+
+const (
+	// Do not reduce
+	ReduceNone Reduction = iota
+	// Mean of losses
+	ReduceMean
+	// Sum of losses
+	ReduceSum
+	// Escape hatch in case new options become available
+	Other
+)
+
+func (r Reduction) ToInt() (retVal int) {
+	switch r {
+	case ReduceNone:
+		return 0
+	case ReduceMean:
+		return 1
+	case ReduceSum:
+		return 2
+	case Other:
+		return 3
+	}
+	return
+}