Skip adding parents if not needed (#922)

Author: ishii-norimi

lib/model/nns/graph.js

@@ -142,7 +142,7 @@ export default class ComputationalGraph {
 		}
 		let parentinfos = []
 		if (!inputs) {
-			if (this._nodes.length > 0) {
+			if (layer.calc.length > 0 && this._nodes.length > 0) {
 				parentinfos.push({
 					index: this._nodes.length - 1,
 					subscript: null,

tests/lib/model/nns/graph.test.js

@@ -185,6 +185,14 @@ describe('Computational Graph', () => {
 			expect(graph.nodes[1].parents[0].subscript).toBeNull()
 		})
 
+		test('no input', () => {
+			const graph = new ComputationalGraph()
+			graph.add(Layer.fromObject({ type: 'input', name: 'a' }))
+			graph.add(Layer.fromObject({ type: 'const', value: 1 }))
+
+			expect(graph.nodes[1].parents).toHaveLength(0)
+		})
+
 		test('string input', () => {
 			const graph = new ComputationalGraph()
 			graph.add(Layer.fromObject({ type: 'input' }), 'in')