使用NVIDIA Nsight Tegra建立OpenCL项目

本文的主要内容是使用NVIDIA提供的Nsight Tegra软件建立OpenCL项目，测试设备为Nexus 7 2013 WiFi版(Android 4.4.4)。

主要参考的资料为“高通平台下安卓opencl小例子”^[1]，“基于 Android* 操作系统的 OpenCL™ 入门”^[2]。

写这篇文章的目的是因为资料[1]中使用的是Eclipse作为开发工具，而用Eclipse+NDK开发感觉调试时不是很方便，而用集成在Visual Studio中的Nsight Tegra调试还是比较方便的。而且[1]中的OpenCL代码是写在C源文件中的，如果.cl文件内容较多时，看起来比较奇怪。

1.需要准备的工具软件(我现在正在使用的版本)

• Visual Studio 2013
• NVIDIA® Nsight™ Tegra®, Visual Studio Edition 3.0
• Android NDK r10e
• AdrenoSDK
• libOpenCL.so

其中AdrenoSDK需要在高通的官方网站下载，实际上只需要用到里面的几个CL头文件，文章末尾会提供下载，这样就不需要下载AdrenoSDK了；libOpenCL.so需要在你用adb pull命令从自己的测试设备上提取到PC机上。例如.so文件在/system/vendor/lib/目录下，就在PC上的命令行里面运行 adb pull /system/vendor/lib/libOpenCL.so 就好了^[1]。

2.具体步骤

各种软件的安装就不在赘述了。

新建项目，如图所示，选择Hello World Demo。

 

先生成一下项目，如果出现下面这样的错误，那就是Target API Level设置有误，因为我的Nexus 7的系统是4.4.4，所以选android-19。

在项目属性页面设置修改“Min Android API Level”和“Target Android API Level”。

xml文件里面也要修改。

这样就可以看到Hello World Demo编译成功的消息了。如果还有其它错误就根据输出的错误信息自行检查一下吧。

看到Demo编译成功，就可以进行下一步的操作了。

首先，如图所示，在项目文件夹下面添加include和lib文件夹，把CL文件夹(文章末尾会提供下载)复制到include里，把libOpenCL.so复制到lib里。

这样做的目的是后面可以使用到相对路径。然后在项目属性里面分别修改如下几个地方(主要就是引用OpenCL的头文件和库文件)。

添加完后重新生成一下，无错误就可以继续下去。

修改HelloJni.java的内容如下。

  1 /*
  2  * Copyright (C) 2009 The Android Open Source Project
  3  *
  4  * Licensed under the Apache License, Version 2.0 (the "License");
  5  * you may not use this file except in compliance with the License.
  6  * You may obtain a copy of the License at
  7  *
  8  *      http://www.apache.org/licenses/LICENSE-2.0
  9  *
 10  * Unless required by applicable law or agreed to in writing, software
 11  * distributed under the License is distributed on an "AS IS" BASIS,
 12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 13  * See the License for the specific language governing permissions and
 14  * limitations under the License.
 15  */
 16 package com.example.hellojni;
 17 
 18 import java.io.BufferedReader;
 19 import java.io.IOException;
 20 import java.io.InputStream;
 21 import java.io.InputStreamReader;
 22 
 23 import android.app.Activity;
 24 import android.widget.TextView;
 25 import android.os.Bundle;
 26 
 27 public class HelloJni extends Activity
 28 {
 29     private TextView tv;
 30 
 31     /** Called when the activity is first created. */
 32     @Override
 33     public void onCreate(Bundle savedInstanceState)
 34     {
 35         super.onCreate(savedInstanceState);
 36 
 37         /*
 38          * Create a TextView and set its content. the text is retrieved by
 39          * calling a native function.
 40          */
 41         tv = new TextView(this);
 42         tv.setText(initOpenCL(getOpenCLProgram()));
 43         setContentView(tv);
 44     }
 45 
 46     private String getOpenCLProgram()
 47     {
 48         /*
 49          * OpenCL program text is stored in a separate file in assets directory.
 50          * Here you need to load it as a single string.
 51          *
 52          * In fact, the program may be directly built into native source code
 53          * where OpenCL API is used, it is useful for short kernels (few lines)
 54          * because it doesn't involve loading code and you don't need to pass it
 55          * from Java to native side.
 56          */
 57 
 58         try
 59         {
 60             StringBuilder buffer = new StringBuilder();
 61             InputStream stream = getAssets().open("step.cl");
 62             BufferedReader reader = new BufferedReader(new InputStreamReader(
 63                         stream));
 64             String s;
 65 
 66             while ((s = reader.readLine()) != null)
 67             {
 68                 buffer.append(s);
 69                 buffer.append("\n");
 70             }
 71 
 72             reader.close();
 73             return buffer.toString();
 74         }
 75         catch (IOException e)
 76         {
 77             e.printStackTrace();
 78         }
 79         return "";
 80 
 81     }
 82 
 83     /*
 84      * A native method that is implemented by the 'Android4' native library,
 85      * which is packaged with this application.
 86      */
 87 
 88     /*
 89      * This is another native method declaration that is *not* implemented by
 90      * 'Android4'. This is simply to show that you can declare as many native
 91      * methods in your Java code as you want, their implementation is searched
 92      * in the currently loaded native libraries only the first time you call
 93      * them.
 94      *
 95      * Trying to call this function will result in a
 96      * java.lang.UnsatisfiedLinkError exception !
 97      */
 98 
 99     private native String initOpenCL(String openCLProgramText);
100 
101     public native String testOpenCL();
102 
103     public native String getPlatformName();
104 
105     public native String getDeviceName();
106 
107     /*
108      * this is used to load the 'Android4' library on application startup. The
109      * library has already been unpacked into
110      * /data/data/com.example.HelloJni/lib/libAndroid4.so at installation time
111      * by the package manager.
112      */
113     static
114     {
115         System.loadLibrary("AndroidOpenCL");
116     }
117 }

HelloJni.java

在jni文件夹下面添加HelloJni.h，内容如下。

 1 /* DO NOT EDIT THIS FILE - it is machine generated */
 2 #include 
 3 /* Header for class com_example_ocl_MainActivity */
 4 
 5 #ifndef HelloJni
 6 #define HelloJni
 7 #ifdef __cplusplus
 8 extern "C" {
 9 #endif
10     /*
11     * Class:     com_example_ocl_MainActivity
12     * Method:    testopencl
13     * Signature: ()Ljava/lang/String;
14     */
15     JNIEXPORT jstring JNICALL Java_com_example_hellojni_HelloJni_testOpenCL(
16         JNIEnv *, jobject);
17 
18     /*
19     * Class:     com_example_ocl_MainActivity
20     * Method:    getPlatformName
21     * Signature: ()Ljava/lang/String;
22     */
23     JNIEXPORT jstring JNICALL Java_com_example_hellojni_HelloJni_getPlatformName(
24         JNIEnv *, jobject);
25 
26     /*
27     * Class:     com_example_ocl_MainActivity
28     * Method:    getDeviceName
29     * Signature: ()Ljava/lang/String;
30     */
31     JNIEXPORT jstring JNICALL Java_com_example_hellojni_HelloJni_getDeviceName(
32         JNIEnv *, jobject);
33 
34     JNIEXPORT jstring JNICALL Java_com_example_hellojni_HelloJni_initOpenCL(
35         JNIEnv *, jobject, jstring openCLProgramText);
36 
37 #ifdef __cplusplus
38 }
39 #endif
40 #endif
41 void Init_OpenCL();
42 void Context_cmd();
43 void Create_Buffer(int *data);
44 void Create_program();
45 void Set_arg();
46 void Execution();
47 void CopyOutResult(int*out);

HelloJni.h

修改HelloJni.cpp的内容如下。

  1 #include 
  2 #include <string.h>
  3 #include 
  4 #include 
  5 #include <malloc.h>
  6 #include 
  7 #include "HelloJni.h"
  8 
  9 #define LEN(arr) sizeof(arr) / sizeof(arr[0])
 10 #define N 1024
 11 #define NUM_THREAD 128
 12 
 13 cl_uint num_device;
 14 cl_uint num_platform;
 15 cl_platform_id *platform;
 16 cl_device_id *devices;
 17 cl_int err;
 18 cl_context context;
 19 cl_command_queue cmdQueue;
 20 cl_mem buffer, sum_buffer;
 21 cl_program program;
 22 cl_kernel kernel;
 23 char src[10240];
 24 int num_block;
 25 
 26 int test()
 27 {
 28     int* in, *out;
 29     num_block = N / NUM_THREAD;
 30     in = (int*)malloc(sizeof(int) * N);
 31     out = (int*)malloc(sizeof(int) * num_block);
 32     for (int i = 0; i < N; i++)
 33     {
 34         in[i] = 1;
 35     }
 36     Init_OpenCL();
 37     Context_cmd();
 38     Create_Buffer(in);
 39     Create_program();
 40     Set_arg();
 41     Execution();
 42     CopyOutResult(out);
 43     int sum = 0;
 44     for (int i = 0; i < num_block; i++)
 45     {
 46         sum += out[i];
 47     }
 48     return sum;
 49 }
 50 /* This is a trivial JNI example where we use a native method
 51 * to return a new VM String. See the corresponding Java source
 52 */
 53 extern "C"
 54 JNIEXPORT jstring JNICALL
 55 Java_com_example_hellojni_HelloJni_testOpenCL(JNIEnv* env, jobject thiz)
 56 {
 57     char result[10];
 58     sprintf(result, "%d\n", test());
 59     return env->NewStringUTF(result);
 60 }
 61 
 62 extern "C"
 63 JNIEXPORT jstring JNICALL
 64 Java_com_example_hellojni_HelloJni_getPlatformName(JNIEnv* env, jobject thiz)
 65 {
 66     char buffer[1024];
 67     clGetPlatformInfo(platform[0], CL_PLATFORM_NAME, sizeof(buffer), buffer,
 68         NULL);
 69     return env->NewStringUTF(buffer);
 70 }
 71 
 72 extern "C"
 73 JNIEXPORT jstring JNICALL
 74 Java_com_example_hellojni_HelloJni_getDeviceName(JNIEnv* env, jobject thiz)
 75 {
 76     char buffer[1024];
 77     clGetDeviceInfo(devices[0], CL_DEVICE_NAME, sizeof(buffer), buffer, NULL);
 78     return env->NewStringUTF(buffer);
 79 }
 80 
 81 extern "C"
 82 JNIEXPORT jstring JNICALL
 83 Java_com_example_hellojni_HelloJni_initOpenCL(JNIEnv* env, jobject thiz,
 84 jstring openCLProgramText)
 85 {
 86     const char* openCLProgramTextNative = env->GetStringUTFChars(
 87         openCLProgramText, 0);
 88     strcpy(src, openCLProgramTextNative);
 89     char result[10];
 90     sprintf(result, "%d\n", test());
 91     return env->NewStringUTF(result);
 92 }
 93 
 94 void Init_OpenCL()
 95 {
 96     size_t nameLen1;
 97     char platformName[1024];
 98 
 99     err = clGetPlatformIDs(0, 0, &num_platform);
100     platform = (cl_platform_id*)malloc(sizeof(cl_platform_id) * num_platform);
101     err = clGetPlatformIDs(num_platform, platform, NULL);
102 
103     err = clGetDeviceIDs(platform[0], CL_DEVICE_TYPE_GPU, 0, NULL, &num_device);
104     devices = (cl_device_id*)malloc(sizeof(cl_device_id) * num_device);
105     err = clGetDeviceIDs(platform[0], CL_DEVICE_TYPE_GPU, num_device, devices,
106         NULL);
107 
108 }
109 
110 void Context_cmd()
111 {
112     context = clCreateContext(NULL, num_device, devices, NULL, NULL, &err);
113     cmdQueue = clCreateCommandQueue(context, devices[0], 0, &err);
114 }
115 
116 void Create_Buffer(int *data)
117 {
118 
119     buffer = clCreateBuffer(context, CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR,
120         sizeof(int) * N, data, &err);
121     sum_buffer = clCreateBuffer(context, CL_MEM_WRITE_ONLY,
122         sizeof(int) * num_block, 0, &err);
123 }
124 
125 void Create_program()
126 {
127     const char * src0 = src;
128     program = clCreateProgramWithSource(context, LEN(&src0), &src0, NULL, NULL);
129     err = clBuildProgram(program, num_device, devices, NULL, NULL, NULL);
130     kernel = clCreateKernel(program, "redution", NULL);
131 }
132 
133 void Set_arg()
134 {
135     err = clSetKernelArg(kernel, 0, sizeof(cl_mem), &buffer);
136     err = clSetKernelArg(kernel, 1, sizeof(cl_mem), &sum_buffer);
137     err = clSetKernelArg(kernel, 2, sizeof(int) * NUM_THREAD, NULL);
138 }
139 
140 void Execution()
141 {
142     const size_t globalWorkSize[1] = { N };
143     const size_t localWorkSize[1] = { NUM_THREAD };
144     err = clEnqueueNDRangeKernel(cmdQueue, kernel, 1, NULL, globalWorkSize,
145         localWorkSize, 0, NULL, NULL);
146     clFinish(cmdQueue);
147 }
148 
149 void CopyOutResult(int*out)
150 {
151     err = clEnqueueReadBuffer(cmdQueue, sum_buffer, CL_TRUE, 0,
152         sizeof(int) * num_block, out, 0, NULL, NULL);
153 }

HelloJni.cpp

在jni文件夹下面添加Application.mk，内容如下。

APP_ABI := armeabi-v7a

Application.mk

在jni文件夹下面添加Android.mk，内容如下。

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE    := AndroidOpenCL
LOCAL_SRC_FILES := HelloJni.cpp
LOCAL_LDFLAGS += -llog  -lOpenCL
include $(BUILD_SHARED_LIBRARY)

Android.mk

在项目中添加assets文件夹，在此文件夹内新建step.cl文件，内容如下。

 1 __kernel void redution(
 2     __global int *data,
 3     __global int *output,
 4     __local int *data_local
 5     )
 6 {
 7     int gid = get_group_id(0);
 8     int tid = get_global_id(0);
 9     int size = get_local_size(0);
10     int id = get_local_id(0);
11     data_local[id] = data[tid];
12     barrier(CLK_LOCAL_MEM_FENCE);
13     for (int i = size / 2; i>0; i >>= 1)
14     {
15         if (id<i)
16         {
17             data_local[id] += data_local[id + i];
18         }
19         barrier(CLK_LOCAL_MEM_FENCE);
20     }
21     if (id == 0)
22     {
23         output[gid] = data_local[0];
24     }
25 }

step.cl

最终解决方案资源管理器里看起来是这个样子的(显示所有文件状态)。

这样就可以重新生成再运行了。需要调试的话，直接在cpp文件中打断点就行了，很方便。

3.资源下载

整个工程的打包文件，其中包含了CL文件夹和libOpenCL.so文件，注意，这里的libOpenCL.so文件是从Nexus 7 2013 WiFi版中提取的，可能不适合你的设备。

链接: http://pan.baidu.com/s/1sjl04JN 密码: 6xtt

4.参考资料

[1]wcj0626,高通平台下安卓opencl小例子,2014.05.19,http://blog.csdn.net/wcj0626/article/details/26272019

[2]Vadim Kartoshkin (Intel),基于 Android* 操作系统的 OpenCL™ 入门,2014.05.12,https://software.intel.com/zh-cn/android/articles/opencl-basic-sample-for-android-os?utm_campaign=eoe&utm_source=eoe.cn&utm_medium=Link&utm_content=intel-optimization

PS：

第一次写技术blog，各位见谅，如有问题，欢迎讨论~

转载于:https://www.cnblogs.com/mjyang/p/4597987.html