Task delegate 6: Refactor the way to configure num_threads

In ImageClassifier, ImageClassifierOptions contains both BaseOptions and NumThreads (configured through the legacy API). Previously, NumThreads is merged into BaseOptions in the JNI layer of ImageClassifier. This new refactor merges NumThreads into BaseOptions in the Java layer, which simplifies the logic a little bit and helps to reduce complexity when adding BaseOptions into the other tasks.

PiperOrigin-RevId: 400223492

Author: lu-wang-g

tensorflow_lite_support/java/src/java/org/tensorflow/lite/task/core/TaskJniUtils.java

@@ -147,7 +147,7 @@ public static MappedByteBuffer loadMappedFile(Context context, String filePath)
   }
 
   /**
-   * Try load a native library, if it's already loaded return directly.
+   * Try loading a native library, if it's already loaded return directly.
    *
    * @param libName name of the lib
    */
@@ -162,8 +162,17 @@ public static void tryLoadLibrary(String libName) {
   }
 
   public static long createProtoBaseOptionsHandle(BaseOptions baseOptions) {
+    return createProtoBaseOptionsHandleWithLegacyNumThreads(baseOptions, /*legacyNumThreads =*/ -1);
+  }
+
+  public static long createProtoBaseOptionsHandleWithLegacyNumThreads(
+      BaseOptions baseOptions, int legacyNumThreads) {
+    // NumThreads should be configured through BaseOptions. However, if NumThreads is configured
+    // through the legacy API of the Task Java API (then it will not equal to -1, the default
+    // value), use it to overide the one in baseOptions.
     return createProtoBaseOptions(
-        baseOptions.getComputeSettings().getDelegate().getValue(), baseOptions.getNumThreads());
+        baseOptions.getComputeSettings().getDelegate().getValue(),
+        legacyNumThreads == -1 ? baseOptions.getNumThreads() : legacyNumThreads);
   }
 
   private TaskJniUtils() {}

tensorflow_lite_support/java/src/java/org/tensorflow/lite/task/vision/classifier/ImageClassifier.java

@@ -144,7 +144,8 @@ public long createHandle(
                     fileDescriptorLength,
                     fileDescriptorOffset,
                     options,
-                    TaskJniUtils.createProtoBaseOptionsHandle(options.getBaseOptions()));
+                    TaskJniUtils.createProtoBaseOptionsHandleWithLegacyNumThreads(
+                        options.getBaseOptions(), options.getNumThreads()));
               }
             },
             IMAGE_CLASSIFIER_NATIVE_LIB,
@@ -175,7 +176,8 @@ public long createHandle() {
                       /*fileDescriptorLength=*/ OPTIONAL_FD_LENGTH,
                       /*fileDescriptorOffset=*/ OPTIONAL_FD_OFFSET,
                       options,
-                      TaskJniUtils.createProtoBaseOptionsHandle(options.getBaseOptions()));
+                      TaskJniUtils.createProtoBaseOptionsHandleWithLegacyNumThreads(
+                          options.getBaseOptions(), options.getNumThreads()));
                 }
               },
               IMAGE_CLASSIFIER_NATIVE_LIB));
@@ -209,7 +211,8 @@ public long createHandle() {
                 return initJniWithByteBuffer(
                     modelBuffer,
                     options,
-                    TaskJniUtils.createProtoBaseOptionsHandle(options.getBaseOptions()));
+                    TaskJniUtils.createProtoBaseOptionsHandleWithLegacyNumThreads(
+                        options.getBaseOptions(), options.getNumThreads()));
               }
             },
             IMAGE_CLASSIFIER_NATIVE_LIB));

tensorflow_lite_support/java/src/native/task/vision/classifier/image_classifier_jni.cc

@@ -100,20 +100,6 @@ ImageClassifierOptions ConvertToProtoOptions(JNIEnv* env, jobject java_options,
   for (const auto& class_name : deny_list_vector) {
     proto_options.add_class_name_blacklist(class_name);
   }
-
-  jmethodID num_threads_id =
-      env->GetMethodID(java_options_class, "getNumThreads", "()I");
-  jint num_threads = env->CallIntMethod(java_options, num_threads_id);
-  // Use base_options to configure num_threads, because image_classifier is
-  // created using base_options in initJniWithModelFdAndOptions and
-  // initJniWithByteBuffer.
-  if (num_threads != -1) {
-    proto_options.mutable_base_options()
-        ->mutable_compute_settings()
-        ->mutable_tflite_settings()
-        ->mutable_cpu_settings()
-        ->set_num_threads(num_threads);
-  }
   return proto_options;
 }