harmony 鸿蒙Using MindSpore Lite Native APIs to Develop AI Applications

  • 2023-10-30
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Using MindSpore Lite Native APIs to Develop AI Applications

Scenarios

You can use the native APIs provided by MindSpore Lite to deploy AI algorithms and provides APIs for the UI layer to invoke the algorithms for model inference. A typical scenario is the AI SDK development.

Basic concepts

  • N-API: a set of native APIs used to build JavaScript components. N-APIs can be used to encapsulate libraries developed using C/C++ into JavaScript modules.

Preparing the Environment

  • Install DevEco Studio 3.1.0.500 or later, and update the SDK to API version 10 or later.

How to Develop

1. Create a native C++ project.

Open DevEco Studio, choose File > New > Create Project to create a native C++ template project. By default, the entry/src/main/ directory of the created project contains the cpp/ directory. You can store C/C++ code in this directory and provide JavaScript APIs for the UI layer to call the code.

2. Compile the C++ inference code.

Assume that you have prepared a model in the .ms format.

Before using the Native APIs provided by MindSpore Lite for development, you need to reference the corresponding header files.

#include <iostream>
#include <mindspore/model.h>
#include <mindspore/context.h>
#include <mindspore/status.h>
#include <mindspore/tensor.h>
#include <rawfile/raw_file_manager.h>

(1). Read model files.

void *ReadModelFile(NativeResourceManager *nativeResourceManager, const std::string &modelName, size_t *modelSize) {
    auto rawFile = OH_ResourceManager_OpenRawFile(nativeResourceManager, modelName.c_str());
    if (rawFile == nullptr) {
        LOGE("Open model file failed");
        return nullptr;
    }
    long fileSize = OH_ResourceManager_GetRawFileSize(rawFile);
    void *modelBuffer = malloc(fileSize);
    if (modelBuffer == nullptr) {
        LOGE("Get model file size failed");
    }
    int ret = OH_ResourceManager_ReadRawFile(rawFile, modelBuffer, fileSize);
    if (ret == 0) {
        LOGI("Read model file failed");
        OH_ResourceManager_CloseRawFile(rawFile);
        return nullptr;
    }
    OH_ResourceManager_CloseRawFile(rawFile);
    *modelSize = fileSize;
    return modelBuffer;
}

(2). Create a context, set parameters such as the number of threads and device type, and load the model.

void DestroyModelBuffer(void **buffer) {
    if (buffer == nullptr) {
        return;
    }
    free(*buffer);
    *buffer = nullptr;
}

OH_AI_ModelHandle CreateMSLiteModel(void *modelBuffer, size_t modelSize) {
    // Create a context.
    auto context = OH_AI_ContextCreate();
    if (context == nullptr) {
        DestroyModelBuffer(&modelBuffer);
        LOGE("Create MSLite context failed.\n");
        return nullptr;
    }
    auto cpu_device_info = OH_AI_DeviceInfoCreate(OH_AI_DEVICETYPE_CPU);
    OH_AI_ContextAddDeviceInfo(context, cpu_device_info);

    // Load the .ms model file.
    auto model = OH_AI_ModelCreate();
    if (model == nullptr) {
        DestroyModelBuffer(&modelBuffer);
        LOGE("Allocate MSLite Model failed.\n");
        return nullptr;
    }

    auto build_ret = OH_AI_ModelBuild(model, modelBuffer, modelSize, OH_AI_MODELTYPE_MINDIR, context);
    DestroyModelBuffer(&modelBuffer);
    if (build_ret != OH_AI_STATUS_SUCCESS) {
        OH_AI_ModelDestroy(&model);
        LOGE("Build MSLite model failed.\n");
        return nullptr;
    }
    LOGI("Build MSLite model success.\n");
    return model;
}

(3). Set the model input data, perform model inference, and obtain the output data.

#define GET_PARAMS(env, info, num)    \
    size_t argc = num;                \
    napi_value argv[num] = {nullptr}; \
    napi_value thisVar = nullptr;     \
    void *data = nullptr;             \
    napi_get_cb_info(env, info, &argc, argv, &thisVar, &data)

constexpr int kNumPrintOfOutData = 10;
constexpr int RANDOM_RANGE = 128;

void FillTensorWithRandom(OH_AI_TensorHandle msTensor) {
    auto size = OH_AI_TensorGetDataSize(msTensor);
    char *data = (char *)OH_AI_TensorGetMutableData(msTensor);
    for (size_t i = 0; i < size; i++) {
        data[i] = (char)(rand() / RANDOM_RANGE);
    }
}

// fill data to inputs tensor
int FillInputTensors(OH_AI_TensorHandleArray &inputs) {
    for (size_t i = 0; i < inputs.handle_num; i++) {
        FillTensorWithRandom(inputs.handle_list[i]);
    }
    return OH_AI_STATUS_SUCCESS;
}

void RunMSLiteModel(OH_AI_ModelHandle model) {
    // Set the model input data.
    auto inputs = OH_AI_ModelGetInputs(model);
    FillInputTensors(inputs);

    auto outputs = OH_AI_ModelGetOutputs(model);
    
    // Perform inference and print the output.
    auto predict_ret = OH_AI_ModelPredict(model, inputs, &outputs, nullptr, nullptr);
    if (predict_ret != OH_AI_STATUS_SUCCESS) {
        OH_AI_ModelDestroy(&model);
        LOGE("Predict MSLite model error.\n");
        return;
    }
    LOGI("Run MSLite model success.\n");

    LOGI("Get model outputs:\n");
    for (size_t i = 0; i < outputs.handle_num; i++) {
        auto tensor = outputs.handle_list[i];
        LOGI("- Tensor %{public}d name is: %{public}s.\n", static_cast<int>(i), OH_AI_TensorGetName(tensor));
        LOGI("- Tensor %{public}d size is: %{public}d.\n", static_cast<int>(i), (int)OH_AI_TensorGetDataSize(tensor));
        auto out_data = reinterpret_cast<const float *>(OH_AI_TensorGetData(tensor));
        std::cout << "Output data is:";
        for (int i = 0; (i < OH_AI_TensorGetElementNum(tensor)) && (i <= kNumPrintOfOutData); i++) {
            std::cout << out_data[i] << " ";
        }
        std::cout << std::endl;
    }
    OH_AI_ModelDestroy(&model);
}

(4). Implement a complete model inference process.

static napi_value RunDemo(napi_env env, napi_callback_info info)
{
    LOGI("Enter runDemo()");
    GET_PARAMS(env, info, 2);
    napi_value error_ret;
    napi_create_int32(env, -1, &error_ret);
    
    const std::string modelName = "ml_headpose.ms";
    size_t modelSize;
    auto resourcesManager = OH_ResourceManager_InitNativeResourceManager(env, argv[1]);
    auto modelBuffer = ReadModelFile(resourcesManager, modelName, &modelSize);
    if (modelBuffer == nullptr) {
        LOGE("Read model failed");
        return error_ret;
    }
    LOGI("Read model file success");

    auto model = CreateMSLiteModel(modelBuffer, modelSize);
    if (model == nullptr) {
        OH_AI_ModelDestroy(&model);
        LOGE("MSLiteFwk Build model failed.\n");
        return error_ret;
    }

    RunMSLiteModel(model);

    napi_value success_ret;
    napi_create_int32(env, 0, &success_ret);

    LOGI("Exit runDemo()");
    return success_ret;
}

(5). Write the CMake script to link the MindSpore Lite dynamic library libmindspore_lite_ndk.so.

cmake_minimum_required(VERSION 3.4.1)
project(OHOSMSLiteNapi)

set(NATIVERENDER_ROOT_PATH ${CMAKE_CURRENT_SOURCE_DIR})

include_directories(${NATIVERENDER_ROOT_PATH}
                    ${NATIVERENDER_ROOT_PATH}/include)

add_library(mslite_napi SHARED mslite_napi.cpp)
target_link_libraries(mslite_napi PUBLIC mindspore_lite_ndk) # MindSpore Lite dynamic library to link
target_link_libraries(mslite_napi PUBLIC hilog_ndk.z)
target_link_libraries(mslite_napi PUBLIC rawfile.z)
target_link_libraries(mslite_napi PUBLIC ace_napi.z)

3. Use N-APIs to encapsulate C++ dynamic libraries into JavaScript modules.

Create the libmslite_api/ subdirectory in entry/src/main/cpp/types/, and create the index.d.ts file in the subdirectory. The file content is as follows:

export const runDemo: (a:String, b:Object) => number;

Use the preceding code to define the JavaScript API runDemo().

In addition, add the oh-package.json5 file to associate the API with the .so file to form a complete JavaScript module.

{
  "name": "libmslite_napi.so",
  "types": "./index.d.ts"
}

4. Invoke the encapsulated MindSpore module in the UI code.

In entry/src/ets/MainAbility/pages/index.ets, define the onClick() event and call the encapsulated runDemo() API in the event callback.

import hilog from '@ohos.hilog'
import msliteNapi from'libmslite_napi.so' // Import the msliteNapi module.
import resManager from '@ohos.resourceManager'

const TAG = 'MSLiteNativeDemo'

@Entry
@Component
struct Index {
    @State message: string = 'MindSpore Lite Demo'
    build() {
        Row() {
            Column() {
                Text(this.message)
                    .fontSize(30)
                    .fontWeight(FontWeight.Bold)
                    .onClick(() => {
                        resManager.getResourceManager().then(mgr => {
                            hilog.info(0x0000, TAG, '*** Start MSLite Demo ***');
                            let ret: number = 0;
                            ret = msliteNapi.runDemo("", mgr); // Call runDemo() to perform AI model inference.
                            if (ret == -1) {
                                hilog.info(0x0000, TAG, 'Error when running MSLite Demo!');
                            }
                            hilog.info(0x0000, TAG, '*** Finished MSLite Demo ***');
                        })
                    })
            }
            .width('100%')
        }
        .height('100%')
    }
}

Debugging and Verification

On DevEco Studio, connect to the device and click Run entry. The following log is generated for the application process:

08-08 16:55:33.766 1513-1529/com.mslite.native_demo I A00000/MSLiteNativeDemo: *** Start MSLite Demo ***
08-08 16:55:33.766 1513-1529/com.mslite.native_demo I A00000/[MSLiteNapi]: Enter runDemo()
08-08 16:55:33.772 1513-1529/com.mslite.native_demo I A00000/[MSLiteNapi]: Read model file success
08-08 16:55:33.799 1513-1529/com.mslite.native_demo I A00000/[MSLiteNapi]: Build MSLite model success.
08-08 16:55:33.818 1513-1529/com.mslite.native_demo I A00000/[MSLiteNapi]: Run MSLite model success.
08-08 16:55:33.818 1513-1529/com.mslite.native_demo I A00000/[MSLiteNapi]: Get model outputs:
08-08 16:55:33.818 1513-1529/com.mslite.native_demo I A00000/[MSLiteNapi]: - Tensor 0 name is: output_node_0.
08-08 16:55:33.818 1513-1529/com.mslite.native_demo I A00000/[MSLiteNapi]: - Tensor 0 size is: 12.
08-08 16:55:33.826 1513-1529/com.mslite.native_demo I A00000/[MSLiteNapi]: Exit runDemo()
08-08 16:55:33.827 1513-1529/com.mslite.native_demo I A00000/MSLiteNativeDemo: *** Finished MSLite Demo ***

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