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• Why won't this piece of my code write to file

  - by user2934783

  I am developing a c++ banking system. I am able to get the float, newbal, values correctly and when I try to write to file, there is no data in the file. else { file>>firstname>>lastname; cout<<endl<<firstname<<" "<<lastname<<endl; cout<<"-----------------------------------\n"; string line; while (getline(file, line)) { //stringstream the getline for line string in file istringstream iss(line); if (iss >> date >> amount) { cout<<date<<"\t\t$"<<showpoint<<fixed<<setprecision(2)<<amount<<endl; famount+=amount; } } cout<<"Your balance is $"<<famount<<endl; cout<<"How much would you like to deposit today: $"; cin>>amountinput; float newbal=0; newbal=(famount+=amountinput); cout<<"\nYour new balance is: $"<<newbal<<".\n"; file<<date<<"\t\t"<<newbal; //***This should be writing to file but it doesn't. file.close(); The text file looks like this: Tony Gaddis 05/24/12 100 05/30/12 300 07/01/12 -300 //Console Output looks like this Tony Gaddis 05/24/12 100 05/30/12 300 07/01/12 -300 Your balance is: #1 How much wuld you like to deposit: #2 Your new balance is: #1 + #2 write to file close file. //exits to main loop:::: How can I make it write to file and save it, and why is this happening. I tried doing it with ostringstream as well considering how I used istringstream for the input. But it didn't work either :\ float newbal=0; newbal=(famount+=amountinput); ostringstream oss(newbal); oss<<date<<"\t\t"<<newbal; I am trying to self teach c++ so any relevant information would be kindly appreciated.

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• Input not cleared.

  - by SoulBeaver

  As the question says, for some reason my program is not flushing the input or using my variables in ways that I cannot identify at the moment. This is for a homework project that I've gone beyond what I had to do for it, now I just want the program to actually work :P Details to make the finding easier: The program executes flawlessly on the first run through. All throws work, only the proper values( n 0 ) are accepted and turned into binary. As soon as I enter my terminate input, the program goes into a loop and only asks for the termiante again like so: When I run this program on Netbeans on my Linux Laptop, the program crashes after I input the terminate value. On Visual C++ on Windows it goes into the loop like just described. In the code I have tried to clear every stream and initialze every variable new as the program restarts, but to no avail. I just can't see my mistake. I believe the error to lie in either the main function: int main( void ) { vector<int> store; int terminate = 1; do { int num = 0; string input = ""; if( cin.fail() ) { cin.clear(); cin.ignore( numeric_limits<streamsize>::max(), '\n' ); } cout << "Please enter a natural number." << endl; readLine( input, num ); cout << "\nThank you. Number is being processed..." << endl; workNum( num, store ); line; cout << "Go again? 0 to terminate." << endl; cin >> terminate // No checking yet, just want it to work! cin.clear(); }while( terminate ); cin.get(); return 0; } or in the function that reads the number: void readLine( string &input, int &num ) { int buf = 1; stringstream ss; vec_sz size; if( ss.fail() ) { ss.clear(); ss.ignore( numeric_limits<streamsize>::max(), '\n' ); } if( getline( cin, input ) ) { size = input.size(); for( int loop = 0; loop < size; ++loop ) if( isalpha( input[loop] ) ) throw domain_error( "Invalid Input." ); ss << input; ss >> buf; if( buf <= 0 ) throw domain_error( "Invalid Input." ); num = buf; ss.clear(); } }

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• sendto: Network unreachable

  - by devin

  Hello. I have two machines I'm testing my code on, one works fine, the other I'm having some problems and I don't know why it is. I'm using an object (C++) for the networking part of my project. On the server side, I do this: (error checking removed for clarity) res = getaddrinfo(NULL, port, &hints, &server)) < 0 for(p=server; p!=NULL; p=p->ai_next){ fd = socket(p->ai_family, p->ai_socktype, p->ai_protocol); if(fd<0){ continue; } if(bind(fd, p->ai_addr, p->ai_addrlen)<0){ close(fd); continue; } break; } This all works. I then make an object with this constructor net::net(int fd, struct sockaddr *other, socklen_t *other_len){ int counter; this->fd = fd; if(other != NULL){ this->other.sa_family = other->sa_family; for(counter=0;counter<13;counter++) this->other.sa_data[counter]=other->sa_data[counter]; } else cerr << "Networking error" << endl; this->other_len = *other_len; } void net::gsend(string s){ if(sendto(this->fd, s.c_str(), s.size()+1, 0, &(this->other), this->other_len)<0){ cerr << "Error Sending, " << s << endl; cerr << strerror(errno) << endl; } return; } string net::grecv(){ stringstream ss; string s; char buf[BUFSIZE]; buf[BUFSIZE-1] = '\0'; if(recvfrom(this->fd, buf, BUFSIZE-1, 0, &(this->other), &(this->other_len))<0){ cerr << "Error Recieving\n"; cerr << strerror(errno) << endl; } // convert to c++ string and if there are multiple trailing ';' remove them ss << buf; s=ss.str(); while(s.find(";;", s.size()-2) != string::npos) s.erase(s.size()-1,1); return s; } So my problem is, is that on one machine, everything works fine. On another, everything works fine until I call my server's gsend() function. In which I get a "Error: Network Unreachable." I call gercv() first before calling gsend() too. Can anyone help me? I would really appreciate it.

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• Signals and threads - good or bad design decision?

  - by Jens

  I have to write a program that performs highly computationally intensive calculations. The program might run for several days. The calculation can be separated easily in different threads without the need of shared data. I want a GUI or a web service that informs me of the current status. My current design uses BOOST::signals2 and BOOST::thread. It compiles and so far works as expected. If a thread finished one iteration and new data is available it calls a signal which is connected to a slot in the GUI class. My question(s): Is this combination of signals and threads a wise idea? I another forum somebody advised someone else not to "go down this road". Are there potential deadly pitfalls nearby that I failed to see? Is my expectation realistic that it will be "easy" to use my GUI class to provide a web interface or a QT, a VTK or a whatever window? Is there a more clever alternative (like other boost libs) that I overlooked? following code compiles with g++ -Wall -o main -lboost_thread-mt <filename>.cpp code follows: #include <boost/signals2.hpp> #include <boost/thread.hpp> #include <boost/bind.hpp> #include <iostream> #include <iterator> #include <string> using std::cout; using std::cerr; using std::string; /** * Called when a CalcThread finished a new bunch of data. */ boost::signals2::signal<void(string)> signal_new_data; /** * The whole data will be stored here. */ class DataCollector { typedef boost::mutex::scoped_lock scoped_lock; boost::mutex mutex; public: /** * Called by CalcThreads call the to store their data. */ void push(const string &s, const string &caller_name) { scoped_lock lock(mutex); _data.push_back(s); signal_new_data(caller_name); } /** * Output everything collected so far to std::out. */ void out() { typedef std::vector<string>::const_iterator iter; for (iter i = _data.begin(); i != _data.end(); ++i) cout << " " << *i << "\n"; } private: std::vector<string> _data; }; /** * Several of those can calculate stuff. * No data sharing needed. */ struct CalcThread { CalcThread(string name, DataCollector &datcol) : _name(name), _datcol(datcol) { } /** * Expensive algorithms will be implemented here. * @param num_results how many data sets are to be calculated by this thread. */ void operator()(int num_results) { for (int i = 1; i <= num_results; ++i) { std::stringstream s; s << "["; if (i == num_results) s << "LAST "; s << "DATA " << i << " from thread " << _name << "]"; _datcol.push(s.str(), _name); } } private: string _name; DataCollector &_datcol; }; /** * Maybe some VTK or QT or both will be used someday. */ class GuiClass { public: GuiClass(DataCollector &datcol) : _datcol(datcol) { } /** * If the GUI wants to present or at least count the data collected so far. * @param caller_name is the name of the thread whose data is new. */ void slot_data_changed(string caller_name) const { cout << "GuiClass knows: new data from " << caller_name << std::endl; } private: DataCollector & _datcol; }; int main() { DataCollector datcol; GuiClass mc(datcol); signal_new_data.connect(boost::bind(&GuiClass::slot_data_changed, &mc, _1)); CalcThread r1("A", datcol), r2("B", datcol), r3("C", datcol), r4("D", datcol), r5("E", datcol); boost::thread t1(r1, 3); boost::thread t2(r2, 1); boost::thread t3(r3, 2); boost::thread t4(r4, 2); boost::thread t5(r5, 3); t1.join(); t2.join(); t3.join(); t4.join(); t5.join(); datcol.out(); cout << "\nDone" << std::endl; return 0; }

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• template class: ctor against function -> new C++ standard

  - by Oops

  Hi in this question: http://stackoverflow.com/questions/2779155/template-point2-double-point3-double Dennis and Michael noticed the unreasonable foolishly implemented constructor. They were right, I didn't consider this at that moment. But I found out that a constructor does not help very much for a template class like this one, instead a function is here much more convenient and safe namespace point { template < unsigned int dims, typename T > struct Point { T X[ dims ]; std::string str() { std::stringstream s; s << "{"; for ( int i = 0; i < dims; ++i ) { s << " X" << i << ": " << X[ i ] << (( i < dims -1 )? " |": " "); } s << "}"; return s.str(); } Point<dims, int> toint() { Point<dims, int> ret; std::copy( X, X+dims, ret.X ); return ret; } }; template < typename T > Point< 2, T > Create( T X0, T X1 ) { Point< 2, T > ret; ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; return ret; } template < typename T > Point< 3, T > Create( T X0, T X1, T X2 ) { Point< 3, T > ret; ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; ret.X[ 2 ] = X2; return ret; } template < typename T > Point< 4, T > Create( T X0, T X1, T X2, T X3 ) { Point< 4, T > ret; ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; ret.X[ 2 ] = X2; ret.X[ 3 ] = X3; return ret; } }; int main( void ) { using namespace point; Point< 2, double > p2d = point::Create( 12.3, 34.5 ); Point< 3, double > p3d = point::Create( 12.3, 34.5, 56.7 ); Point< 4, double > p4d = point::Create( 12.3, 34.5, 56.7, 78.9 ); //Point< 3, double > p1d = point::Create( 12.3, 34.5 ); //no suitable user defined conversion exists //Point< 3, int > p1i = p4d.toint(); //no suitable user defined conversion exists Point< 2, int > p2i = p2d.toint(); Point< 3, int > p3i = p3d.toint(); Point< 4, int > p4i = p4d.toint(); std::cout << p2d.str() << std::endl; std::cout << p3d.str() << std::endl; std::cout << p4d.str() << std::endl; std::cout << p2i.str() << std::endl; std::cout << p3i.str() << std::endl; std::cout << p4i.str() << std::endl; char c; std::cin >> c; } has the new C++ standard any new improvements, language features or simplifications regarding this aspect of ctor of a template class? what do you think about the implementation of the combination of namespace, stuct and Create function? many thanks in advance Oops

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• Generic Aggregation of C++ Objects by Attribute When Attribute Name is Unknown at Runtime

  - by stretch

  I'm currently implementing a system with a number of class's representing objects such as client, business, product etc. Standard business logic. As one might expect each class has a number of standard attributes. I have a long list of essentially identical requirements such as: the ability to retrieve all business' whose industry is manufacturing. the ability to retrieve all clients based in London Class business has attribute sector and client has attribute location. Clearly this a relational problem and in pseudo SQL would look something like: SELECT ALL business in business' WHERE sector == manufacturing Unfortunately plugging into a DB is not an option. What I want to do is have a single generic aggregation function whose signature would take the form: vector<generic> genericAggregation(class, attribute, value); Where class is the class of object I want to aggregate, attribute and value being the class attribute and value of interest. In my example I've put vector as return type, but this wouldn't work. Probably better to declare a vector of relevant class type and pass it as an argument. But this isn't the main problem. How can I accept arguments in string form for class, attribute and value and then map these in a generic object aggregation function? Since it's rude not to post code, below is a dummy program which creates a bunch of objects of imaginatively named classes. Included is a specific aggregation function which returns a vector of B objects whose A object is equal to an id specified at the command line e.g. .. $ ./aggregations 5 which returns all B's whose A objects 'i' attribute is equal to 5. See below: #include <iostream> #include <cstring> #include <sstream> #include <vector> using namespace std; //First imaginativly names dummy class class A { private: int i; double d; string s; public: A(){} A(int i, double d, string s) { this->i = i; this->d = d; this->s = s; } ~A(){} int getInt() {return i;} double getDouble() {return d;} string getString() {return s;} }; //second imaginativly named dummy class class B { private: int i; double d; string s; A *a; public: B(int i, double d, string s, A *a) { this->i = i; this->d = d; this->s = s; this->a = a; } ~B(){} int getInt() {return i;} double getDouble() {return d;} string getString() {return s;} A* getA() {return a;} }; //Containers for dummy class objects vector<A> a_vec (10); vector<B> b_vec;//100 //Util function, not important.. string int2string(int number) { stringstream ss; ss << number; return ss.str(); } //Example function that returns a new vector containing on B objects //whose A object i attribute is equal to 'id' vector<B> getBbyA(int id) { vector<B> result; for(int i = 0; i < b_vec.size(); i++) { if(b_vec.at(i).getA()->getInt() == id) { result.push_back(b_vec.at(i)); } } return result; } int main(int argc, char** argv) { //Create some A's and B's, each B has an A... //Each of the 10 A's are associated with 10 B's. for(int i = 0; i < 10; ++i) { A a(i, (double)i, int2string(i)); a_vec.at(i) = a; for(int j = 0; j < 10; j++) { B b((i * 10) + j, (double)j, int2string(i), &a_vec.at(i)); b_vec.push_back(b); } } //Got some objects so lets do some aggregation //Call example aggregation function to return all B objects //whose A object has i attribute equal to argv[1] vector<B> result = getBbyA(atoi(argv[1])); //If some B's were found print them, else don't... if(result.size() != 0) { for(int i = 0; i < result.size(); i++) { cout << result.at(i).getInt() << " " << result.at(i).getA()->getInt() << endl; } } else { cout << "No B's had A's with attribute i equal to " << argv[1] << endl; } return 0; } Compile with: g++ -o aggregations aggregations.cpp If you wish :) Instead of implementing a separate aggregation function (i.e. getBbyA() in the example) I'd like to have a single generic aggregation function which accounts for all possible class attribute pairs such that all aggregation requirements are met.. and in the event additional attributes are added later, or additional aggregation requirements, these will automatically be accounted for. So there's a few issues here but the main one I'm seeking insight into is how to map a runtime argument to a class attribute. I hope I've provided enough detail to adequately describe what I'm trying to do...

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• OpenCL: Strange buffer or image bahaviour with NVidia but not Amd

  - by Alex R.

  I have a big problem (on Linux): I create a buffer with defined data, then an OpenCL kernel takes this data and puts it into an image2d_t. When working on an AMD C50 (Fusion CPU/GPU) the program works as desired, but on my GeForce 9500 GT the given kernel computes the correct result very rarely. Sometimes the result is correct, but very often it is incorrect. Sometimes it depends on very strange changes like removing unused variable declarations or adding a newline. I realized that disabling the optimization will increase the probability to fail. I have the most actual display driver in both systems. Here is my reduced code: #include <CL/cl.h> #include <string> #include <iostream> #include <sstream> #include <cmath> void checkOpenCLErr(cl_int err, std::string name){ const char* errorString[] = { "CL_SUCCESS", "CL_DEVICE_NOT_FOUND", "CL_DEVICE_NOT_AVAILABLE", "CL_COMPILER_NOT_AVAILABLE", "CL_MEM_OBJECT_ALLOCATION_FAILURE", "CL_OUT_OF_RESOURCES", "CL_OUT_OF_HOST_MEMORY", "CL_PROFILING_INFO_NOT_AVAILABLE", "CL_MEM_COPY_OVERLAP", "CL_IMAGE_FORMAT_MISMATCH", "CL_IMAGE_FORMAT_NOT_SUPPORTED", "CL_BUILD_PROGRAM_FAILURE", "CL_MAP_FAILURE", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "CL_INVALID_VALUE", "CL_INVALID_DEVICE_TYPE", "CL_INVALID_PLATFORM", "CL_INVALID_DEVICE", "CL_INVALID_CONTEXT", "CL_INVALID_QUEUE_PROPERTIES", "CL_INVALID_COMMAND_QUEUE", "CL_INVALID_HOST_PTR", "CL_INVALID_MEM_OBJECT", "CL_INVALID_IMAGE_FORMAT_DESCRIPTOR", "CL_INVALID_IMAGE_SIZE", "CL_INVALID_SAMPLER", "CL_INVALID_BINARY", "CL_INVALID_BUILD_OPTIONS", "CL_INVALID_PROGRAM", "CL_INVALID_PROGRAM_EXECUTABLE", "CL_INVALID_KERNEL_NAME", "CL_INVALID_KERNEL_DEFINITION", "CL_INVALID_KERNEL", "CL_INVALID_ARG_INDEX", "CL_INVALID_ARG_VALUE", "CL_INVALID_ARG_SIZE", "CL_INVALID_KERNEL_ARGS", "CL_INVALID_WORK_DIMENSION", "CL_INVALID_WORK_GROUP_SIZE", "CL_INVALID_WORK_ITEM_SIZE", "CL_INVALID_GLOBAL_OFFSET", "CL_INVALID_EVENT_WAIT_LIST", "CL_INVALID_EVENT", "CL_INVALID_OPERATION", "CL_INVALID_GL_OBJECT", "CL_INVALID_BUFFER_SIZE", "CL_INVALID_MIP_LEVEL", "CL_INVALID_GLOBAL_WORK_SIZE", }; if (err != CL_SUCCESS) { std::stringstream str; str << errorString[-err] << " (" << err << ")"; throw std::string(name)+(str.str()); } } int main(){ try{ cl_context m_context; cl_platform_id* m_platforms; unsigned int m_numPlatforms; cl_command_queue m_queue; cl_device_id m_device; cl_int error = 0; // Used to handle error codes clGetPlatformIDs(0,NULL,&m_numPlatforms); m_platforms = new cl_platform_id[m_numPlatforms]; error = clGetPlatformIDs(m_numPlatforms,m_platforms,&m_numPlatforms); checkOpenCLErr(error, "getPlatformIDs"); // Device error = clGetDeviceIDs(m_platforms[0], CL_DEVICE_TYPE_GPU, 1, &m_device, NULL); checkOpenCLErr(error, "getDeviceIDs"); // Context cl_context_properties properties[] = { CL_CONTEXT_PLATFORM, (cl_context_properties)(m_platforms[0]), 0}; m_context = clCreateContextFromType(properties, CL_DEVICE_TYPE_GPU, NULL, NULL, NULL); // m_private->m_context = clCreateContext(properties, 1, &m_private->m_device, NULL, NULL, &error); checkOpenCLErr(error, "Create context"); // Command-queue m_queue = clCreateCommandQueue(m_context, m_device, 0, &error); checkOpenCLErr(error, "Create command queue"); //Build program and kernel const char* source = "#pragma OPENCL EXTENSION cl_khr_byte_addressable_store : enable\n" "\n" "__kernel void bufToImage(__global unsigned char* in, __write_only image2d_t out, const unsigned int offset_x, const unsigned int image_width , const unsigned int maxval ){\n" "\tint i = get_global_id(0);\n" "\tint j = get_global_id(1);\n" "\tint width = get_global_size(0);\n" "\tint height = get_global_size(1);\n" "\n" "\tint pos = j*image_width*3+(offset_x+i)*3;\n" "\tif( maxval < 256 ){\n" "\t\tfloat4 c = (float4)(in[pos],in[pos+1],in[pos+2],1.0f);\n" "\t\tc.x /= maxval;\n" "\t\tc.y /= maxval;\n" "\t\tc.z /= maxval;\n" "\t\twrite_imagef(out, (int2)(i,j), c);\n" "\t}else{\n" "\t\tfloat4 c = (float4)(255.0f*in[2*pos]+in[2*pos+1],255.0f*in[2*pos+2]+in[2*pos+3],255.0f*in[2*pos+4]+in[2*pos+5],1.0f);\n" "\t\tc.x /= maxval;\n" "\t\tc.y /= maxval;\n" "\t\tc.z /= maxval;\n" "\t\twrite_imagef(out, (int2)(i,j), c);\n" "\t}\n" "}\n" "\n" "__constant sampler_t imageSampler = CLK_NORMALIZED_COORDS_FALSE | CLK_ADDRESS_CLAMP_TO_EDGE | CLK_FILTER_NEAREST;\n" "\n" "__kernel void imageToBuf(__read_only image2d_t in, __global unsigned char* out, const unsigned int offset_x, const unsigned int image_width ){\n" "\tint i = get_global_id(0);\n" "\tint j = get_global_id(1);\n" "\tint pos = j*image_width*3+(offset_x+i)*3;\n" "\tfloat4 c = read_imagef(in, imageSampler, (int2)(i,j));\n" "\tif( c.x <= 1.0f && c.y <= 1.0f && c.z <= 1.0f ){\n" "\t\tout[pos] = c.x*255.0f;\n" "\t\tout[pos+1] = c.y*255.0f;\n" "\t\tout[pos+2] = c.z*255.0f;\n" "\t}else{\n" "\t\tout[pos] = 200.0f;\n" "\t\tout[pos+1] = 0.0f;\n" "\t\tout[pos+2] = 255.0f;\n" "\t}\n" "}\n"; cl_int err; cl_program prog = clCreateProgramWithSource(m_context,1,&source,NULL,&err); if( -err != CL_SUCCESS ) throw std::string("clCreateProgramWithSources"); err = clBuildProgram(prog,0,NULL,"-cl-opt-disable",NULL,NULL); if( -err != CL_SUCCESS ) throw std::string("clBuildProgram(fromSources)"); cl_kernel kernel = clCreateKernel(prog,"bufToImage",&err); checkOpenCLErr(err,"CreateKernel"); cl_uint imageWidth = 8; cl_uint imageHeight = 9; //Initialize datas cl_uint maxVal = 255; cl_uint offsetX = 0; int size = imageWidth*imageHeight*3; int resSize = imageWidth*imageHeight*4; cl_uchar* data = new cl_uchar[size]; cl_float* expectedData = new cl_float[resSize]; for( int i = 0,j=0; i < size; i++,j++ ){ data[i] = (cl_uchar)i; expectedData[j] = (cl_float)i/255.0f; if ( i%3 == 2 ){ j++; expectedData[j] = 1.0f; } } cl_mem inBuffer = clCreateBuffer(m_context,CL_MEM_READ_ONLY|CL_MEM_COPY_HOST_PTR,size*sizeof(cl_uchar),data,&err); checkOpenCLErr(err, "clCreateBuffer()"); clFinish(m_queue); cl_image_format imgFormat; imgFormat.image_channel_order = CL_RGBA; imgFormat.image_channel_data_type = CL_FLOAT; cl_mem outImg = clCreateImage2D( m_context, CL_MEM_READ_WRITE, &imgFormat, imageWidth, imageHeight, 0, NULL, &err ); checkOpenCLErr(err,"get2DImage()"); clFinish(m_queue); size_t kernelRegion[]={imageWidth,imageHeight}; size_t kernelWorkgroup[]={1,1}; //Fill kernel with data clSetKernelArg(kernel,0,sizeof(cl_mem),&inBuffer); clSetKernelArg(kernel,1,sizeof(cl_mem),&outImg); clSetKernelArg(kernel,2,sizeof(cl_uint),&offsetX); clSetKernelArg(kernel,3,sizeof(cl_uint),&imageWidth); clSetKernelArg(kernel,4,sizeof(cl_uint),&maxVal); //Run kernel err = clEnqueueNDRangeKernel(m_queue,kernel,2,NULL,kernelRegion,kernelWorkgroup,0,NULL,NULL); checkOpenCLErr(err,"RunKernel"); clFinish(m_queue); //Check resulting data for validty cl_float* computedData = new cl_float[resSize];; size_t region[]={imageWidth,imageHeight,1}; const size_t offset[] = {0,0,0}; err = clEnqueueReadImage(m_queue,outImg,CL_TRUE,offset,region,0,0,computedData,0,NULL,NULL); checkOpenCLErr(err, "readDataFromImage()"); clFinish(m_queue); for( int i = 0; i < resSize; i++ ){ if( fabs(expectedData[i]-computedData[i])>0.1 ){ std::cout << "Expected: \n"; for( int j = 0; j < resSize; j++ ){ std::cout << expectedData[j] << " "; } std::cout << "\nComputed: \n"; std::cout << "\n"; for( int j = 0; j < resSize; j++ ){ std::cout << computedData[j] << " "; } std::cout << "\n"; throw std::string("Error, computed and expected data are not the same!\n"); } } }catch(std::string& e){ std::cout << "\nCaught an exception: " << e << "\n"; return 1; } std::cout << "Works fine\n"; return 0; } I also uploaded the source code for you to make it easier to test it: http://www.file-upload.net/download-3513797/strangeOpenCLError.cpp.html Please can you tell me if I've done wrong anything? Is there any mistake in the code or is this a bug in my driver? Best reagards, Alex

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• JNI String Corruption

  - by Chris Dennett

  Hi everyone, I'm getting weird string corruption across JNI calls which is causing problems on the the Java side. Every so often, I'll get a corrupted string in the passed array, which sometimes has existing parts of the original non-corrupted string. The C++ code is supposed to set the first index of the array to the address, it's a nasty hack to get around method call limitations. Additionally, the application is multi-threaded. remoteaddress[0]: 10.1.1.2:49153 remoteaddress[0]: 10.1.4.2:49153 remoteaddress[0]: 10.1.6.2:49153 remoteaddress[0]: 10.1.2.2:49153 remoteaddress[0]: 10.1.9.2:49153 remoteaddress[0]: {garbage here} java.lang.NullPointerException at kokuks.KKSAddress.<init>(KKSAddress.java:139) at kokuks.KKSAddress.createAddress(KKSAddress.java:48) at kokuks.KKSSocket._recvFrom(KKSSocket.java:963) at kokuks.scheduler.RecvOperation$1.execute(RecvOperation.java:144) at kokuks.scheduler.RecvOperation$1.execute(RecvOperation.java:1) at kokuks.KKSEvent.run(KKSEvent.java:58) at kokuks.KokuKS.handleJNIEventExpiry(KokuKS.java:872) at kokuks.KokuKS.handleJNIEventExpiry_fjni(KokuKS.java:880) at kokuks.KokuKS.runSimulator_jni(Native Method) at kokuks.KokuKS$1.run(KokuKS.java:773) at java.lang.Thread.run(Thread.java:717) remoteaddress[0]: 10.1.7.2:49153 The null pointer exception comes from trying to use the corrupt string. In C++, the address prints to standard out normally, but doing this reduces the rate of errors, from what I can see. The C++ code (if it helps): /* * Class: kokuks_KKSSocket * Method: recvFrom_jni * Signature: (Ljava/lang/String;[Ljava/lang/String;Ljava/nio/ByteBuffer;IIJ)I */ JNIEXPORT jint JNICALL Java_kokuks_KKSSocket_recvFrom_1jni (JNIEnv *env, jobject obj, jstring sockpath, jobjectArray addrarr, jobject buf, jint position, jint limit, jlong flags) { if (addrarr && env->GetArrayLength(addrarr) > 0) { env->SetObjectArrayElement(addrarr, 0, NULL); } jboolean iscopy; const char* cstr = env->GetStringUTFChars(sockpath, &iscopy); std::string spath = std::string(cstr); env->ReleaseStringUTFChars(sockpath, cstr); // release me! if (KKS_DEBUG) { std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << std::endl; } ns3::Ptr<ns3::Socket> socket = ns3::Names::Find<ns3::Socket>(spath); if (!socket) { std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " socket not found for path!!" << std::endl; return -1; // not found } if (!addrarr) { std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " array to set sender is null" << std::endl; return -1; } jsize arrsize = env->GetArrayLength(addrarr); if (arrsize < 1) { std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " array too small to set sender!" << std::endl; return -1; } uint8_t* bufaddr = (uint8_t*)env->GetDirectBufferAddress(buf); long bufcap = env->GetDirectBufferCapacity(buf); uint8_t* realbufaddr = bufaddr + position; uint32_t remaining = limit - position; if (KKS_DEBUG) { std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " bufaddr: " << bufaddr << ", cap: " << bufcap << std::endl; } ns3::Address aaddr; uint32_t mflags = flags; int ret = socket->RecvFrom(realbufaddr, remaining, mflags, aaddr); if (ret > 0) { if (KKS_DEBUG) std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " addr: " << aaddr << std::endl; ns3::InetSocketAddress insa = ns3::InetSocketAddress::ConvertFrom(aaddr); std::stringstream ss; insa.GetIpv4().Print(ss); ss << ":" << insa.GetPort() << std::ends; if (KKS_DEBUG) std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " addr: " << ss.str() << std::endl; jsize index = 0; const char *cstr = ss.str().c_str(); jstring jaddr = env->NewStringUTF(cstr); if (jaddr == NULL) std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " jaddr is null!!" << std::endl; //jaddr = (jstring)env->NewGlobalRef(jaddr); env->SetObjectArrayElement(addrarr, index, jaddr); //if (env->ExceptionOccurred()) { // env->ExceptionDescribe(); //} } jint jret = ret; return jret; } The Java code (if it helps): /** * Pass an array of size 1 into remote address, and this will be set with * the sender of the packet (hax). This emulates C++ references. * * @param remoteaddress * @param buf * @param flags * @return */ public int _recvFrom(final KKSAddress remoteaddress[], ByteBuffer buf, long flags) { if (!kks.isCurrentlyThreadSafe()) throw new RuntimeException( "Not currently thread safe for ns-3 functions!" ); //lock.lock(); try { if (!buf.isDirect()) return -6; // not direct!! final String[] remoteAddrStr = new String[1]; int ret = 0; ret = recvFrom_jni( path.toPortableString(), remoteAddrStr, buf, buf.position(), buf.limit(), flags ); if (ret > 0) { System.out.println("remoteaddress[0]: " + remoteAddrStr[0]); remoteaddress[0] = KKSAddress.createAddress(remoteAddrStr[0]); buf.position(buf.position() + ret); } return ret; } finally { errNo = _getErrNo(); //lock.unlock(); } } public int recvFrom(KKSAddress[] fromaddress, final ByteBuffer bytes, long flags, long timeoutMS) { if (KokuKS.DEBUG_MODE) printMessage("public synchronized int recvFrom(KKSAddress[] fromaddress, final ByteBuffer bytes, long flags, long timeoutMS)"); if (kks.isCurrentlyThreadSafe()) { return _recvFrom(fromaddress, bytes, flags); // avoid event } fromaddress[0] = null; RecvOperation ro = new RecvOperation( kks, this, flags, true, bytes, timeoutMS ); ro.start(); fromaddress[0] = ro.getFrom(); return ro.getRetCode(); }

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• Using R to Analyze G1GC Log Files

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  Using R to Analyze G1GC Log Files   Using R to Analyze G1GC Log Files Introduction Working in Oracle Platform Integration gives an engineer opportunities to work on a wide array of technologies. My team’s goal is to make Oracle applications run best on the Solaris/SPARC platform. When looking for bottlenecks in a modern applications, one needs to be aware of not only how the CPUs and operating system are executing, but also network, storage, and in some cases, the Java Virtual Machine. I was recently presented with about 1.5 GB of Java Garbage First Garbage Collector log file data. If you’re not familiar with the subject, you might want to review Garbage First Garbage Collector Tuning by Monica Beckwith. The customer had been running Java HotSpot 1.6.0_31 to host a web application server. I was told that the Solaris/SPARC server was running a Java process launched using a commmand line that included the following flags: -d64 -Xms9g -Xmx9g -XX:+UseG1GC -XX:MaxGCPauseMillis=200 -XX:InitiatingHeapOccupancyPercent=80 -XX:PermSize=256m -XX:MaxPermSize=256m -XX:+PrintGC -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC -XX:+PrintGCDateStamps -XX:+PrintFlagsFinal -XX:+DisableExplicitGC -XX:+UnlockExperimentalVMOptions -XX:ParallelGCThreads=8 Several sources on the internet indicate that if I were to print out the 1.5 GB of log files, it would require enough paper to fill the bed of a pick up truck. Of course, it would be fruitless to try to scan the log files by hand. Tools will be required to summarize the contents of the log files. Others have encountered large Java garbage collection log files. There are existing tools to analyze the log files: IBM’s GC toolkit The chewiebug GCViewer gchisto HPjmeter Instead of using one of the other tools listed, I decide to parse the log files with standard Unix tools, and analyze the data with R. Data Cleansing The log files arrived in two different formats. I guess that the difference is that one set of log files was generated using a more verbose option, maybe -XX:+PrintHeapAtGC, and the other set of log files was generated without that option. Format 1 In some of the log files, the log files with the less verbose format, a single trace, i.e. the report of a singe garbage collection event, looks like this: {Heap before GC invocations=12280 (full 61): garbage-first heap total 9437184K, used 7499918K [0xfffffffd00000000, 0xffffffff40000000, 0xffffffff40000000) region size 4096K, 1 young (4096K), 0 survivors (0K) compacting perm gen total 262144K, used 144077K [0xffffffff40000000, 0xffffffff50000000, 0xffffffff50000000) the space 262144K, 54% used [0xffffffff40000000, 0xffffffff48cb3758, 0xffffffff48cb3800, 0xffffffff50000000) No shared spaces configured. 2014-05-14T07:24:00.988-0700: 60586.353: [GC pause (young) 7324M->7320M(9216M), 0.1567265 secs] Heap after GC invocations=12281 (full 61): garbage-first heap total 9437184K, used 7496533K [0xfffffffd00000000, 0xffffffff40000000, 0xffffffff40000000) region size 4096K, 0 young (0K), 0 survivors (0K) compacting perm gen total 262144K, used 144077K [0xffffffff40000000, 0xffffffff50000000, 0xffffffff50000000) the space 262144K, 54% used [0xffffffff40000000, 0xffffffff48cb3758, 0xffffffff48cb3800, 0xffffffff50000000) No shared spaces configured. } A simple grep can be used to extract a summary: $ grep "\[ GC pause (young" g1gc.log 2014-05-13T13:24:35.091-0700: 3.109: [GC pause (young) 20M->5029K(9216M), 0.0146328 secs] 2014-05-13T13:24:35.440-0700: 3.459: [GC pause (young) 9125K->6077K(9216M), 0.0086723 secs] 2014-05-13T13:24:37.581-0700: 5.599: [GC pause (young) 25M->8470K(9216M), 0.0203820 secs] 2014-05-13T13:24:42.686-0700: 10.704: [GC pause (young) 44M->15M(9216M), 0.0288848 secs] 2014-05-13T13:24:48.941-0700: 16.958: [GC pause (young) 51M->20M(9216M), 0.0491244 secs] 2014-05-13T13:24:56.049-0700: 24.066: [GC pause (young) 92M->26M(9216M), 0.0525368 secs] 2014-05-13T13:25:34.368-0700: 62.383: [GC pause (young) 602M->68M(9216M), 0.1721173 secs] But that format wasn't easily read into R, so I needed to be a bit more tricky. I used the following Unix command to create a summary file that was easy for R to read. $ echo "SecondsSinceLaunch BeforeSize AfterSize TotalSize RealTime" $ grep "\[GC pause (young" g1gc.log | grep -v mark | sed -e 's/[A-SU-z\(\),]/ /g' -e 's/->/ /' -e 's/: / /g' | more SecondsSinceLaunch BeforeSize AfterSize TotalSize RealTime 2014-05-13T13:24:35.091-0700 3.109 20 5029 9216 0.0146328 2014-05-13T13:24:35.440-0700 3.459 9125 6077 9216 0.0086723 2014-05-13T13:24:37.581-0700 5.599 25 8470 9216 0.0203820 2014-05-13T13:24:42.686-0700 10.704 44 15 9216 0.0288848 2014-05-13T13:24:48.941-0700 16.958 51 20 9216 0.0491244 2014-05-13T13:24:56.049-0700 24.066 92 26 9216 0.0525368 2014-05-13T13:25:34.368-0700 62.383 602 68 9216 0.1721173 Format 2 In some of the log files, the log files with the more verbose format, a single trace, i.e. the report of a singe garbage collection event, was more complicated than Format 1. Here is a text file with an example of a single G1GC trace in the second format. As you can see, it is quite complicated. It is nice that there is so much information available, but the level of detail can be overwhelming. I wrote this awk script (download) to summarize each trace on a single line. #!/usr/bin/env awk -f BEGIN { printf("SecondsSinceLaunch IncrementalCount FullCount UserTime SysTime RealTime BeforeSize AfterSize TotalSize\n") } ###################### # Save count data from lines that are at the start of each G1GC trace. # Each trace starts out like this: # {Heap before GC invocations=14 (full 0): # garbage-first heap total 9437184K, used 325496K [0xfffffffd00000000, 0xffffffff40000000, 0xffffffff40000000) ###################### /{Heap.*full/{ gsub ( "\\)" , "" ); nf=split($0,a,"="); split(a[2],b," "); getline; if ( match($0, "first") ) { G1GC=1; IncrementalCount=b[1]; FullCount=substr( b[3], 1, length(b[3])-1 ); } else { G1GC=0; } } ###################### # Pull out time stamps that are in lines with this format: # 2014-05-12T14:02:06.025-0700: 94.312: [GC pause (young), 0.08870154 secs] ###################### /GC pause/ { DateTime=$1; SecondsSinceLaunch=substr($2, 1, length($2)-1); } ###################### # Heap sizes are in lines that look like this: # [ 4842M->4838M(9216M)] ###################### /\[ .*]$/ { gsub ( "\\[" , "" ); gsub ( "\ \]" , "" ); gsub ( "->" , " " ); gsub ( "\\( " , " " ); gsub ( "\ \)" , " " ); split($0,a," "); if ( split(a[1],b,"M") > 1 ) {BeforeSize=b[1]*1024;} if ( split(a[1],b,"K") > 1 ) {BeforeSize=b[1];} if ( split(a[2],b,"M") > 1 ) {AfterSize=b[1]*1024;} if ( split(a[2],b,"K") > 1 ) {AfterSize=b[1];} if ( split(a[3],b,"M") > 1 ) {TotalSize=b[1]*1024;} if ( split(a[3],b,"K") > 1 ) {TotalSize=b[1];} } ###################### # Emit an output line when you find input that looks like this: # [Times: user=1.41 sys=0.08, real=0.24 secs] ###################### /\[Times/ { if (G1GC==1) { gsub ( "," , "" ); split($2,a,"="); UserTime=a[2]; split($3,a,"="); SysTime=a[2]; split($4,a,"="); RealTime=a[2]; print DateTime,SecondsSinceLaunch,IncrementalCount,FullCount,UserTime,SysTime,RealTime,BeforeSize,AfterSize,TotalSize; G1GC=0; } } The resulting summary is about 25X smaller that the original file, but still difficult for a human to digest. SecondsSinceLaunch IncrementalCount FullCount UserTime SysTime RealTime BeforeSize AfterSize TotalSize ... 2014-05-12T18:36:34.669-0700: 3985.744 561 0 0.57 0.06 0.16 1724416 1720320 9437184 2014-05-12T18:36:34.839-0700: 3985.914 562 0 0.51 0.06 0.19 1724416 1720320 9437184 2014-05-12T18:36:35.069-0700: 3986.144 563 0 0.60 0.04 0.27 1724416 1721344 9437184 2014-05-12T18:36:35.354-0700: 3986.429 564 0 0.33 0.04 0.09 1725440 1722368 9437184 2014-05-12T18:36:35.545-0700: 3986.620 565 0 0.58 0.04 0.17 1726464 1722368 9437184 2014-05-12T18:36:35.726-0700: 3986.801 566 0 0.43 0.05 0.12 1726464 1722368 9437184 2014-05-12T18:36:35.856-0700: 3986.930 567 0 0.30 0.04 0.07 1726464 1723392 9437184 2014-05-12T18:36:35.947-0700: 3987.023 568 0 0.61 0.04 0.26 1727488 1723392 9437184 2014-05-12T18:36:36.228-0700: 3987.302 569 0 0.46 0.04 0.16 1731584 1724416 9437184 Reading the Data into R Once the GC log data had been cleansed, either by processing the first format with the shell script, or by processing the second format with the awk script, it was easy to read the data into R. g1gc.df = read.csv("summary.txt", row.names = NULL, stringsAsFactors=FALSE,sep="") str(g1gc.df) ## 'data.frame': 8307 obs. of 10 variables: ## $ row.names : chr "2014-05-12T14:00:32.868-0700:" "2014-05-12T14:00:33.179-0700:" "2014-05-12T14:00:33.677-0700:" "2014-05-12T14:00:35.538-0700:" ... ## $ SecondsSinceLaunch: num 1.16 1.47 1.97 3.83 6.1 ... ## $ IncrementalCount : int 0 1 2 3 4 5 6 7 8 9 ... ## $ FullCount : int 0 0 0 0 0 0 0 0 0 0 ... ## $ UserTime : num 0.11 0.05 0.04 0.21 0.08 0.26 0.31 0.33 0.34 0.56 ... ## $ SysTime : num 0.04 0.01 0.01 0.05 0.01 0.06 0.07 0.06 0.07 0.09 ... ## $ RealTime : num 0.02 0.02 0.01 0.04 0.02 0.04 0.05 0.04 0.04 0.06 ... ## $ BeforeSize : int 8192 5496 5768 22528 24576 43008 34816 53248 55296 93184 ... ## $ AfterSize : int 1400 1672 2557 4907 7072 14336 16384 18432 19456 21504 ... ## $ TotalSize : int 9437184 9437184 9437184 9437184 9437184 9437184 9437184 9437184 9437184 9437184 ... head(g1gc.df) ## row.names SecondsSinceLaunch IncrementalCount ## 1 2014-05-12T14:00:32.868-0700: 1.161 0 ## 2 2014-05-12T14:00:33.179-0700: 1.472 1 ## 3 2014-05-12T14:00:33.677-0700: 1.969 2 ## 4 2014-05-12T14:00:35.538-0700: 3.830 3 ## 5 2014-05-12T14:00:37.811-0700: 6.103 4 ## 6 2014-05-12T14:00:41.428-0700: 9.720 5 ## FullCount UserTime SysTime RealTime BeforeSize AfterSize TotalSize ## 1 0 0.11 0.04 0.02 8192 1400 9437184 ## 2 0 0.05 0.01 0.02 5496 1672 9437184 ## 3 0 0.04 0.01 0.01 5768 2557 9437184 ## 4 0 0.21 0.05 0.04 22528 4907 9437184 ## 5 0 0.08 0.01 0.02 24576 7072 9437184 ## 6 0 0.26 0.06 0.04 43008 14336 9437184 Basic Statistics Once the data has been read into R, simple statistics are very easy to generate. All of the numbers from high school statistics are available via simple commands. For example, generate a summary of every column: summary(g1gc.df) ## row.names SecondsSinceLaunch IncrementalCount FullCount ## Length:8307 Min. : 1 Min. : 0 Min. : 0.0 ## Class :character 1st Qu.: 9977 1st Qu.:2048 1st Qu.: 0.0 ## Mode :character Median :12855 Median :4136 Median : 12.0 ## Mean :12527 Mean :4156 Mean : 31.6 ## 3rd Qu.:15758 3rd Qu.:6262 3rd Qu.: 61.0 ## Max. :55484 Max. :8391 Max. :113.0 ## UserTime SysTime RealTime BeforeSize ## Min. :0.040 Min. :0.0000 Min. : 0.0 Min. : 5476 ## 1st Qu.:0.470 1st Qu.:0.0300 1st Qu.: 0.1 1st Qu.:5137920 ## Median :0.620 Median :0.0300 Median : 0.1 Median :6574080 ## Mean :0.751 Mean :0.0355 Mean : 0.3 Mean :5841855 ## 3rd Qu.:0.920 3rd Qu.:0.0400 3rd Qu.: 0.2 3rd Qu.:7084032 ## Max. :3.370 Max. :1.5600 Max. :488.1 Max. :8696832 ## AfterSize TotalSize ## Min. : 1380 Min. :9437184 ## 1st Qu.:5002752 1st Qu.:9437184 ## Median :6559744 Median :9437184 ## Mean :5785454 Mean :9437184 ## 3rd Qu.:7054336 3rd Qu.:9437184 ## Max. :8482816 Max. :9437184 Q: What is the total amount of User CPU time spent in garbage collection? sum(g1gc.df$UserTime) ## [1] 6236 As you can see, less than two hours of CPU time was spent in garbage collection. Is that too much? To find the percentage of time spent in garbage collection, divide the number above by total_elapsed_time*CPU_count. In this case, there are a lot of CPU’s and it turns out the the overall amount of CPU time spent in garbage collection isn’t a problem when viewed in isolation. When calculating rates, i.e. events per unit time, you need to ask yourself if the rate is homogenous across the time period in the log file. Does the log file include spikes of high activity that should be separately analyzed? Averaging in data from nights and weekends with data from business hours may alias problems. If you have a reason to suspect that the garbage collection rates include peaks and valleys that need independent analysis, see the “Time Series” section, below. Q: How much garbage is collected on each pass? The amount of heap space that is recovered per GC pass is surprisingly low: At least one collection didn’t recover any data. (“Min.=0”) 25% of the passes recovered 3MB or less. (“1st Qu.=3072”) Half of the GC passes recovered 4MB or less. (“Median=4096”) The average amount recovered was 56MB. (“Mean=56390”) 75% of the passes recovered 36MB or less. (“3rd Qu.=36860”) At least one pass recovered 2GB. (“Max.=2121000”) g1gc.df$Delta = g1gc.df$BeforeSize - g1gc.df$AfterSize summary(g1gc.df$Delta) ## Min. 1st Qu. Median Mean 3rd Qu. Max. ## 0 3070 4100 56400 36900 2120000 Q: What is the maximum User CPU time for a single collection? The worst garbage collection (“Max.”) is many standard deviations away from the mean. The data appears to be right skewed. summary(g1gc.df$UserTime) ## Min. 1st Qu. Median Mean 3rd Qu. Max. ## 0.040 0.470 0.620 0.751 0.920 3.370 sd(g1gc.df$UserTime) ## [1] 0.3966 Basic Graphics Once the data is in R, it is trivial to plot the data with formats including dot plots, line charts, bar charts (simple, stacked, grouped), pie charts, boxplots, scatter plots histograms, and kernel density plots. Histogram of User CPU Time per Collection I don't think that this graph requires any explanation. hist(g1gc.df$UserTime, main="User CPU Time per Collection", xlab="Seconds", ylab="Frequency") Box plot to identify outliers When the initial data is viewed with a box plot, you can see the one crazy outlier in the real time per GC. Save this data point for future analysis and drop the outlier so that it’s not throwing off our statistics. Now the box plot shows many outliers, which will be examined later, using times series analysis. Notice that the scale of the x-axis changes drastically once the crazy outlier is removed. par(mfrow=c(2,1)) boxplot(g1gc.df$UserTime,g1gc.df$SysTime,g1gc.df$RealTime, main="Box Plot of Time per GC\n(dominated by a crazy outlier)", names=c("usr","sys","elapsed"), xlab="Seconds per GC", ylab="Time (Seconds)", horizontal = TRUE, outcol="red") crazy.outlier.df=g1gc.df[g1gc.df$RealTime > 400,] g1gc.df=g1gc.df[g1gc.df$RealTime < 400,] boxplot(g1gc.df$UserTime,g1gc.df$SysTime,g1gc.df$RealTime, main="Box Plot of Time per GC\n(crazy outlier excluded)", names=c("usr","sys","elapsed"), xlab="Seconds per GC", ylab="Time (Seconds)", horizontal = TRUE, outcol="red") box(which = "outer", lty = "solid") Here is the crazy outlier for future analysis: crazy.outlier.df ## row.names SecondsSinceLaunch IncrementalCount ## 8233 2014-05-12T23:15:43.903-0700: 20741 8316 ## FullCount UserTime SysTime RealTime BeforeSize AfterSize TotalSize ## 8233 112 0.55 0.42 488.1 8381440 8235008 9437184 ## Delta ## 8233 146432 R Time Series Data To analyze the garbage collection as a time series, I’ll use Z’s Ordered Observations (zoo). “zoo is the creator for an S3 class of indexed totally ordered observations which includes irregular time series.” require(zoo) ## Loading required package: zoo ## ## Attaching package: 'zoo' ## ## The following objects are masked from 'package:base': ## ## as.Date, as.Date.numeric head(g1gc.df[,1]) ## [1] "2014-05-12T14:00:32.868-0700:" "2014-05-12T14:00:33.179-0700:" ## [3] "2014-05-12T14:00:33.677-0700:" "2014-05-12T14:00:35.538-0700:" ## [5] "2014-05-12T14:00:37.811-0700:" "2014-05-12T14:00:41.428-0700:" options("digits.secs"=3) times=as.POSIXct( g1gc.df[,1], format="%Y-%m-%dT%H:%M:%OS%z:") g1gc.z = zoo(g1gc.df[,-c(1)], order.by=times) head(g1gc.z) ## SecondsSinceLaunch IncrementalCount FullCount ## 2014-05-12 17:00:32.868 1.161 0 0 ## 2014-05-12 17:00:33.178 1.472 1 0 ## 2014-05-12 17:00:33.677 1.969 2 0 ## 2014-05-12 17:00:35.538 3.830 3 0 ## 2014-05-12 17:00:37.811 6.103 4 0 ## 2014-05-12 17:00:41.427 9.720 5 0 ## UserTime SysTime RealTime BeforeSize AfterSize ## 2014-05-12 17:00:32.868 0.11 0.04 0.02 8192 1400 ## 2014-05-12 17:00:33.178 0.05 0.01 0.02 5496 1672 ## 2014-05-12 17:00:33.677 0.04 0.01 0.01 5768 2557 ## 2014-05-12 17:00:35.538 0.21 0.05 0.04 22528 4907 ## 2014-05-12 17:00:37.811 0.08 0.01 0.02 24576 7072 ## 2014-05-12 17:00:41.427 0.26 0.06 0.04 43008 14336 ## TotalSize Delta ## 2014-05-12 17:00:32.868 9437184 6792 ## 2014-05-12 17:00:33.178 9437184 3824 ## 2014-05-12 17:00:33.677 9437184 3211 ## 2014-05-12 17:00:35.538 9437184 17621 ## 2014-05-12 17:00:37.811 9437184 17504 ## 2014-05-12 17:00:41.427 9437184 28672 Example of Two Benchmark Runs in One Log File The data in the following graph is from a different log file, not the one of primary interest to this article. I’m including this image because it is an example of idle periods followed by busy periods. It would be uninteresting to average the rate of garbage collection over the entire log file period. More interesting would be the rate of garbage collect in the two busy periods. Are they the same or different? Your production data may be similar, for example, bursts when employees return from lunch and idle times on weekend evenings, etc. Once the data is in an R Time Series, you can analyze isolated time windows. Clipping the Time Series data Flashing back to our test case… Viewing the data as a time series is interesting. You can see that the work intensive time period is between 9:00 PM and 3:00 AM. Lets clip the data to the interesting period:     par(mfrow=c(2,1)) plot(g1gc.z$UserTime, type="h", main="User Time per GC\nTime: Complete Log File", xlab="Time of Day", ylab="CPU Seconds per GC", col="#1b9e77") clipped.g1gc.z=window(g1gc.z, start=as.POSIXct("2014-05-12 21:00:00"), end=as.POSIXct("2014-05-13 03:00:00")) plot(clipped.g1gc.z$UserTime, type="h", main="User Time per GC\nTime: Limited to Benchmark Execution", xlab="Time of Day", ylab="CPU Seconds per GC", col="#1b9e77") box(which = "outer", lty = "solid") Cumulative Incremental and Full GC count Here is the cumulative incremental and full GC count. When the line is very steep, it indicates that the GCs are repeating very quickly. Notice that the scale on the Y axis is different for full vs. incremental. plot(clipped.g1gc.z[,c(2:3)], main="Cumulative Incremental and Full GC count", xlab="Time of Day", col="#1b9e77") GC Analysis of Benchmark Execution using Time Series data In the following series of 3 graphs: The “After Size” show the amount of heap space in use after each garbage collection. Many Java objects are still referenced, i.e. alive, during each garbage collection. This may indicate that the application has a memory leak, or may indicate that the application has a very large memory footprint. Typically, an application's memory footprint plateau's in the early stage of execution. One would expect this graph to have a flat top. The steep decline in the heap space may indicate that the application crashed after 2:00. The second graph shows that the outliers in real execution time, discussed above, occur near 2:00. when the Java heap seems to be quite full. The third graph shows that Full GCs are infrequent during the first few hours of execution. The rate of Full GC's, (the slope of the cummulative Full GC line), changes near midnight.   plot(clipped.g1gc.z[,c("AfterSize","RealTime","FullCount")], xlab="Time of Day", col=c("#1b9e77","red","#1b9e77")) GC Analysis of heap recovered Each GC trace includes the amount of heap space in use before and after the individual GC event. During garbage coolection, unreferenced objects are identified, the space holding the unreferenced objects is freed, and thus, the difference in before and after usage indicates how much space has been freed. The following box plot and bar chart both demonstrate the same point - the amount of heap space freed per garbage colloection is surprisingly low. par(mfrow=c(2,1)) boxplot(as.vector(clipped.g1gc.z$Delta), main="Amount of Heap Recovered per GC Pass", xlab="Size in KB", horizontal = TRUE, col="red") hist(as.vector(clipped.g1gc.z$Delta), main="Amount of Heap Recovered per GC Pass", xlab="Size in KB", breaks=100, col="red") box(which = "outer", lty = "solid") This graph is the most interesting. The dark blue area shows how much heap is occupied by referenced Java objects. This represents memory that holds live data. The red fringe at the top shows how much data was recovered after each garbage collection. barplot(clipped.g1gc.z[,c("AfterSize","Delta")], col=c("#7570b3","#e7298a"), xlab="Time of Day", border=NA) legend("topleft", c("Live Objects","Heap Recovered on GC"), fill=c("#7570b3","#e7298a")) box(which = "outer", lty = "solid") When I discuss the data in the log files with the customer, I will ask for an explaination for the large amount of referenced data resident in the Java heap. There are two are posibilities: There is a memory leak and the amount of space required to hold referenced objects will continue to grow, limited only by the maximum heap size. After the maximum heap size is reached, the JVM will throw an “Out of Memory” exception every time that the application tries to allocate a new object. If this is the case, the aplication needs to be debugged to identify why old objects are referenced when they are no longer needed. The application has a legitimate requirement to keep a large amount of data in memory. The customer may want to further increase the maximum heap size. Another possible solution would be to partition the application across multiple cluster nodes, where each node has responsibility for managing a unique subset of the data. Conclusion In conclusion, R is a very powerful tool for the analysis of Java garbage collection log files. The primary difficulty is data cleansing so that information can be read into an R data frame. Once the data has been read into R, a rich set of tools may be used for thorough evaluation.

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