libviennacl-dev 1.5.2-2 / usr / include / viennacl / ocl / context.hpp

#ifndef VIENNACL_OCL_CONTEXT_HPP_
#define VIENNACL_OCL_CONTEXT_HPP_

/* =========================================================================
   Copyright (c) 2010-2014, Institute for Microelectronics,
                            Institute for Analysis and Scientific Computing,
                            TU Wien.
   Portions of this software are copyright by UChicago Argonne, LLC.

                            -----------------
                  ViennaCL - The Vienna Computing Library
                            -----------------

   Project Head:    Karl Rupp                   rupp@iue.tuwien.ac.at

   (A list of authors and contributors can be found in the PDF manual)

   License:         MIT (X11), see file LICENSE in the base directory
============================================================================= */

/** @file viennacl/ocl/context.hpp
    @brief Represents an OpenCL context within ViennaCL
*/

#ifdef __APPLE__
#include <OpenCL/cl.h>
#else
#include <CL/cl.h>
#endif

#include <algorithm>
#include <vector>
#include <map>
#include "viennacl/ocl/forwards.h"
#include "viennacl/ocl/handle.hpp"
#include "viennacl/ocl/kernel.hpp"
#include "viennacl/ocl/program.hpp"
#include "viennacl/ocl/device.hpp"
#include "viennacl/ocl/platform.hpp"
#include "viennacl/ocl/command_queue.hpp"

namespace viennacl
{
  namespace ocl
  {
    /** @brief Manages an OpenCL context and provides the respective convenience functions for creating buffers, etc.
      *
      * This class was originally written before the OpenCL C++ bindings were standardized.
      * Regardless, it provides a couple of convience functionality which is not covered by the OpenCL C++ bindings.
    */
    class context
    {
      typedef std::vector< viennacl::ocl::program >   ProgramContainer;

      public:
        context() : initialized_(false),
                    device_type_(CL_DEVICE_TYPE_DEFAULT),
                    current_device_id_(0),
                    default_device_num_(1),
                    pf_index_(0),
                    current_queue_id_(0) {}

        //////// Get and set default number of devices per context */
        /** @brief Returns the maximum number of devices to be set up for the context */
        vcl_size_t default_device_num() const { return default_device_num_; }

        /** @brief Sets the maximum number of devices to be set up for the context */
        void default_device_num(vcl_size_t new_num) { default_device_num_ = new_num; }

        ////////// get and set preferred device type /////////////////////
        /** @brief Returns the default device type for the context */
        cl_device_type default_device_type()
        {
          return device_type_;
        }

        /** @brief Sets the device type for this context */
        void default_device_type(cl_device_type dtype)
        {
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Setting new device type for context " << h_ << std::endl;
          #endif
          if (!initialized_)
            device_type_ = dtype; //assume that the user provided a correct value
        }

        //////////////////// get devices //////////////////
        /** @brief Returns a vector with all devices in this context */
        std::vector<viennacl::ocl::device> const & devices() const
        {
          return devices_;
        }

        /** @brief Returns the current device */
        viennacl::ocl::device const & current_device() const
        {
          //std::cout << "Current device id in context: " << current_device_id_ << std::endl;
          return devices_[current_device_id_];
        }

        /** @brief Switches the current device to the i-th device in this context */
        void switch_device(vcl_size_t i)
        {
          assert(i < devices_.size() && bool("Provided device index out of range!"));
          current_device_id_ = i;
        }

        /** @brief If the supplied device is used within the context, it becomes the current active device. */
        void switch_device(viennacl::ocl::device const & d)
        {
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Setting new current device for context " << h_ << std::endl;
          #endif
          bool found = false;
          for (vcl_size_t i=0; i<devices_.size(); ++i)
          {
            if (devices_[i] == d)
            {
              found = true;
              current_device_id_ = i;
              break;
            }
          }
          if (found == false)
            std::cerr << "ViennaCL: Warning: Could not set device " << d.name() << " for context." << std::endl;
        }

        /** @brief Add a device to the context. Must be done before the context is initialized */
        void add_device(viennacl::ocl::device const & d)
        {
          assert(!initialized_ && bool("Device must be added to context before it is initialized!"));
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Adding new device to context " << h_ << std::endl;
          #endif
          if (std::find(devices_.begin(), devices_.end(), d) == devices_.end())
            devices_.push_back(d);
        }

        /** @brief Add a device to the context. Must be done before the context is initialized */
        void add_device(cl_device_id d)
        {
          assert(!initialized_ && bool("Device must be added to context before it is initialized!"));
          add_device(viennacl::ocl::device(d));
        }


        /////////////////////// initialize context ///////////////////

        /** @brief Initializes a new context */
        void init()
        {
          init_new();
        }

        /** @brief Initializes the context from an existing, user-supplied context */
        void init(cl_context c)
        {
          init_existing(c);
        }

/*        void existing_context(cl_context context_id)
        {
          assert(!initialized_ && bool("ViennaCL: FATAL error: Provided a new context for an already initialized context."));
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Reusing existing context " << h_ << std::endl;
          #endif
          h_ = context_id;
        }*/

        ////////////////////// create memory /////////////////////////////

        /** @brief Creates a memory buffer within the context. Does not wrap the OpenCL handle into the smart-pointer-like viennacl::ocl::handle, which saves an OpenCL backend call, yet the user has to ensure that the OpenCL memory handle is free'd or passed to a viennacl::ocl::handle later on.
        *
        *  @param flags  OpenCL flags for the buffer creation
        *  @param size   Size of the memory buffer in bytes
        *  @param ptr    Optional pointer to CPU memory, with which the OpenCL memory should be initialized
        *  @return       A plain OpenCL handle. Either assign it to a viennacl::ocl::handle<cl_mem> directly, or make sure that you free to memory manually if you no longer need the allocated memory.
        */
        cl_mem create_memory_without_smart_handle(cl_mem_flags flags, unsigned int size, void * ptr = NULL) const
        {
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Creating memory of size " << size << " for context " << h_ << " (unsafe, returning cl_mem directly)" << std::endl;
          #endif
          if (ptr)
            flags |= CL_MEM_COPY_HOST_PTR;
          cl_int err;
          cl_mem mem = clCreateBuffer(h_.get(), flags, size, ptr, &err);
          VIENNACL_ERR_CHECK(err);
          return mem;
        }


        /** @brief Creates a memory buffer within the context
        *
        *  @param flags  OpenCL flags for the buffer creation
        *  @param size   Size of the memory buffer in bytes
        *  @param ptr    Optional pointer to CPU memory, with which the OpenCL memory should be initialized
        */
        viennacl::ocl::handle<cl_mem> create_memory(cl_mem_flags flags, unsigned int size, void * ptr = NULL) const
        {
          return viennacl::ocl::handle<cl_mem>(create_memory_without_smart_handle(flags, size, ptr), *this);
        }

        /** @brief Creates a memory buffer within the context initialized from the supplied data
        *
        *  @param flags  OpenCL flags for the buffer creation
        *  @param buffer A vector (STL vector, ublas vector, etc.)
        */
        template < typename SCALARTYPE, typename A, template <typename, typename> class VectorType >
        viennacl::ocl::handle<cl_mem> create_memory(cl_mem_flags flags, const VectorType<SCALARTYPE, A> & buffer) const
        {
          return viennacl::ocl::handle<cl_mem>(create_memory_without_smart_handle(flags, static_cast<cl_uint>(sizeof(SCALARTYPE) * buffer.size()), (void*)&buffer[0]), *this);
        }

        //////////////////// create queues ////////////////////////////////

        /** @brief Adds an existing queue for the given device to the context */
        void add_queue(cl_device_id dev, cl_command_queue q)
        {
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Adding existing queue " << q << " for device " << dev << " to context " << h_ << std::endl;
          #endif
          viennacl::ocl::handle<cl_command_queue> queue_handle(q, *this);
          queues_[dev].push_back(viennacl::ocl::command_queue(queue_handle));
          queues_[dev].back().handle().inc();
        }

        /** @brief Adds a queue for the given device to the context */
        void add_queue(cl_device_id dev)
        {
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Adding new queue for device " << dev << " to context " << h_ << std::endl;
          #endif
          cl_int err;
#ifdef VIENNACL_PROFILING_ENABLED
          viennacl::ocl::handle<cl_command_queue> temp(clCreateCommandQueue(h_.get(), dev, CL_QUEUE_PROFILING_ENABLE, &err), *this);
#else
          viennacl::ocl::handle<cl_command_queue> temp(clCreateCommandQueue(h_.get(), dev, 0, &err), *this);
#endif
          VIENNACL_ERR_CHECK(err);

          queues_[dev].push_back(viennacl::ocl::command_queue(temp));
        }

        /** @brief Adds a queue for the given device to the context */
        void add_queue(viennacl::ocl::device d) { add_queue(d.id()); }

        //get queue for default device:
        viennacl::ocl::command_queue & get_queue()
        {
          return queues_[devices_[current_device_id_].id()][current_queue_id_];
        }

        viennacl::ocl::command_queue const & get_queue() const
        {
          typedef std::map< cl_device_id, std::vector<viennacl::ocl::command_queue> >    QueueContainer;

          // find queue:
          QueueContainer::const_iterator it = queues_.find(devices_[current_device_id_].id());
          if (it != queues_.end())
            return (it->second)[current_queue_id_];

          std::cerr << "ViennaCL: FATAL ERROR: Could not obtain current command queue!" << std::endl;
          std::cout << "Number of queues in context: " << queues_.size() << std::endl;
          std::cout << "Number of devices in context: " << devices_.size() << std::endl;
          throw "queue not found!";

          //return (it->second)[current_queue_id_];
        }

        //get a particular queue:
        /** @brief Returns the queue with the provided index for the given device */
        viennacl::ocl::command_queue & get_queue(cl_device_id dev, vcl_size_t i = 0)
        {
          assert(i < queues_.size() && bool("In class 'context': id invalid in get_queue()"));
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Getting queue " << i << " for device " << dev << " in context " << h_ << std::endl;
          #endif
          unsigned int device_index;
          for (device_index = 0; device_index < devices_.size(); ++device_index)
          {
            if (devices_[device_index] == dev)
              break;
          }

          assert(device_index < devices_.size() && bool("Device not within context"));

          return queues_[devices_[device_index].id()][i];
        }

        /** @brief Returns the current device */
        // TODO: work out the const issues
        viennacl::ocl::command_queue const & current_queue() //const
        {
          return queues_[devices_[current_device_id_].id()][current_queue_id_];
        }

        /** @brief Switches the current device to the i-th device in this context */
        void switch_queue(vcl_size_t i)
        {
          assert(i < queues_[devices_[current_device_id_].id()].size() && bool("In class 'context': Provided queue index out of range for device!"));
          current_queue_id_ = i;
        }

#if 1
        /** @brief If the supplied command_queue is used within the context, it becomes the current active command_queue, the command_queue's device becomes current active device. */
        void switch_queue(viennacl::ocl::command_queue const & q)
        {
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Setting new current queue for context " << h_ << std::endl;
          #endif
          bool found = false;
          typedef std::map< cl_device_id, std::vector<viennacl::ocl::command_queue> >    QueueContainer;

          // For each device:
          vcl_size_t j = 0;
          for (QueueContainer::const_iterator it=queues_.begin(); it != queues_.end(); it++,j++)
          {
              const std::vector<viennacl::ocl::command_queue> & qv = (it->second);
              // For each queue candidate
              for (vcl_size_t i=0; i<qv.size(); ++i)
              {
                  if (qv[i] == q)
                  {
                      found = true;
                      current_device_id_ = j;
                      current_queue_id_ = i;
                      break;
                  }
              }
          }
          if (found == false)
            std::cerr << "ViennaCL: Warning: Could not set queue " << q.handle().get() << " for context." << std::endl;
        }
#endif

        /////////////////// create program ///////////////////////////////
        /** @brief Adds a program to the context
        */
        viennacl::ocl::program & add_program(cl_program p, std::string const & prog_name)
        {
          programs_.push_back(viennacl::ocl::program(p, *this, prog_name));
          return programs_.back();
        }

        /** @brief Adds a new program with the provided source to the context. Compiles the program and extracts all kernels from it
        */
        viennacl::ocl::program & add_program(std::string const & source, std::string const & prog_name)
        {
          const char * source_text = source.c_str();
          vcl_size_t source_size = source.size();
          cl_int err;

          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Adding program '" << prog_name << "' to context " << h_ << std::endl;
          #endif

          //
          // Build program
          //
          cl_program temp = clCreateProgramWithSource(h_.get(), 1, (const char **)&source_text, &source_size, &err);
          VIENNACL_ERR_CHECK(err);

          const char * options = build_options_.c_str();
          err = clBuildProgram(temp, 0, NULL, options, NULL, NULL);
          if (err != CL_SUCCESS)
          {
            char buffer[8192];
            cl_build_status status;
            clGetProgramBuildInfo(temp, devices_[0].id(), CL_PROGRAM_BUILD_STATUS, sizeof(cl_build_status), &status, NULL);
            clGetProgramBuildInfo(temp, devices_[0].id(), CL_PROGRAM_BUILD_LOG, sizeof(char)*8192, &buffer, NULL);
            std::cout << "Build Scalar: Err = " << err << " Status = " << status << std::endl;
            std::cout << "Log: " << buffer << std::endl;
            std::cout << "Sources: " << source << std::endl;
          }
          VIENNACL_ERR_CHECK(err);

          programs_.push_back(viennacl::ocl::program(temp, *this, prog_name));

          viennacl::ocl::program & prog = programs_.back();

          //
          // Extract kernels
          //
          cl_kernel kernels[1024];
          cl_uint   num_kernels_in_prog;
          err = clCreateKernelsInProgram(prog.handle().get(), 1024, kernels, &num_kernels_in_prog);
          VIENNACL_ERR_CHECK(err);

          for (cl_uint i=0; i<num_kernels_in_prog; ++i)
          {
            char kernel_name[128];
            err = clGetKernelInfo(kernels[i], CL_KERNEL_FUNCTION_NAME, 128, kernel_name, NULL);
            prog.add_kernel(kernels[i], std::string(kernel_name));
          }

          return prog;
        }

        /** @brief Delete the program with the provided name */
        void delete_program(std::string const & name){
          for (ProgramContainer::iterator it = programs_.begin();
                it != programs_.end();
                ++it)
          {
            if (it->name() == name){
              programs_.erase(it);
              return;
            }
          }
        }

        /** @brief Returns the program with the provided name */
        viennacl::ocl::program & get_program(std::string const & name)
        {
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Getting program '" << name << "' from context " << h_ << std::endl;
          #endif
          for (ProgramContainer::iterator it = programs_.begin();
                it != programs_.end();
                ++it)
          {
            if (it->name() == name)
              return *it;
          }
          std::cerr << "Could not find program '" << name << "'" << std::endl;
          throw "In class 'context': name invalid in get_program()";
          //return programs_[0];  //return a defined object
        }

        viennacl::ocl::program const & get_program(std::string const & name) const
        {
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Getting program '" << name << "' from context " << h_ << std::endl;
          #endif
          for (ProgramContainer::const_iterator it = programs_.begin();
                it != programs_.end();
                ++it)
          {
            if (it->name() == name)
              return *it;
          }
          std::cerr << "Could not find program '" << name << "'" << std::endl;
          throw "In class 'context': name invalid in get_program()";
          //return programs_[0];  //return a defined object
        }

        /** @brief Returns whether the program with the provided name exists or not */
        bool has_program(std::string const & name){
            for (ProgramContainer::iterator it = programs_.begin();
                  it != programs_.end();
                  ++it)
            {
              if (it->name() == name) return true;
            }
            return false;
        }

        /** @brief Returns the program with the provided id */
        viennacl::ocl::program & get_program(vcl_size_t id)
        {
          assert(id < programs_.size() && bool("In class 'context': id invalid in get_program()"));
          return programs_[id];
        }

        /** @brief Returns the number of programs within this context */
        vcl_size_t program_num() { return programs_.size(); }

        /** @brief Convenience function for retrieving the kernel of a program directly from the context */
        viennacl::ocl::kernel & get_kernel(std::string const & program_name, std::string const & kernel_name) { return get_program(program_name).get_kernel(kernel_name); }

        /** @brief Returns the number of devices within this context */
        vcl_size_t device_num() { return devices_.size(); }

        /** @brief Returns the context handle */
        const viennacl::ocl::handle<cl_context> & handle() const { return h_; }

        /** @brief Returns the current build option string */
        std::string build_options() const { return build_options_; }

        /** @brief Sets the build option string, which is passed to the OpenCL compiler in subsequent compilations. Does not effect programs already compiled previously. */
        void build_options(std::string op) { build_options_ = op; }

        /** @brief Returns the platform ID of the platform to be used for the context */
        vcl_size_t platform_index() const  { return pf_index_; }

        /** @brief Sets the platform ID of the platform to be used for the context */
        void platform_index(vcl_size_t new_index)
        {
          assert(!initialized_ && bool("Platform ID must be set before context is initialized!"));
          pf_index_ = new_index;
        }

        /** @brief Less-than comparable for compatibility with std:map  */
        bool operator<(context const & other) const
        {
          return h_.get() < other.h_.get();
        }

        bool operator==(context const & other) const
        {
          return h_.get() == other.h_.get();
        }

      private:
        /** @brief Initialize a new context. Reuse any previously supplied information (devices, queues) */
        void init_new()
        {
          assert(!initialized_ && bool("ViennaCL FATAL error: Context already created!"));

          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Initializing new ViennaCL context." << std::endl;
          #endif

          cl_int err;
          std::vector<cl_device_id> device_id_array;
          if (devices_.empty()) //get the default device if user has not yet specified a list of devices
          {
            //create an OpenCL context for the provided devices:
            #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
            std::cout << "ViennaCL: Setting all devices for context..." << std::endl;
            #endif

            platform pf(pf_index_);
            std::vector<device> devices = pf.devices(device_type_);
            #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
            std::cout << "ViennaCL: Number of devices for context: " << devices.size() << std::endl;
            #endif
            vcl_size_t device_num = std::min<vcl_size_t>(default_device_num_, devices.size());
            for (vcl_size_t i=0; i<device_num; ++i)
              devices_.push_back(devices[i]);

            if (devices.size() == 0)
            {
              std::cerr << "ViennaCL: FATAL ERROR: No devices of type '";
              switch (device_type_)
              {
                case CL_DEVICE_TYPE_CPU:          std::cout << "CPU"; break;
                case CL_DEVICE_TYPE_GPU:          std::cout << "GPU"; break;
                case CL_DEVICE_TYPE_ACCELERATOR:  std::cout << "ACCELERATOR"; break;
                case CL_DEVICE_TYPE_DEFAULT:      std::cout << "DEFAULT"; break;
                default:
                  std::cout << "UNKNOWN" << std::endl;
              }
              std::cout << "' found!" << std::endl;
            }
          }

          //extract list of device ids:
          for (std::vector< viennacl::ocl::device >::const_iterator iter = devices_.begin();
                                                                    iter != devices_.end();
                                                                  ++iter)
            device_id_array.push_back(iter->id());

          h_ = clCreateContext(0,
                               static_cast<cl_uint>(devices_.size()),
                               &(device_id_array[0]),
                               NULL, NULL, &err);
          VIENNACL_ERR_CHECK(err);

          initialized_ = true;
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Initialization of new ViennaCL context done." << std::endl;
          #endif
        }

        /** @brief Reuses a supplied context. */
        void init_existing(cl_context c)
        {
          assert(!initialized_ && bool("ViennaCL FATAL error: Context already created!"));
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Initialization of ViennaCL context from existing context." << std::endl;
          #endif

          //set context handle:
          h_ = c;
          h_.inc(); // if the user provides the context, then the user will also call release() on the context. Without inc(), we would get a seg-fault due to double-free at program termination.

          if (devices_.empty())
          {
            //get devices for context:
            cl_int err;
            cl_uint num_devices;
            vcl_size_t temp;
            //Note: The obvious
            //  err = clGetContextInfo(h_, CL_CONTEXT_NUM_DEVICES, sizeof(cl_uint), &num_devices, NULL);
            //does not work with NVIDIA OpenCL stack!
            err = clGetContextInfo(h_.get(), CL_CONTEXT_DEVICES, VIENNACL_OCL_MAX_DEVICE_NUM * sizeof(cl_device_id), NULL, &temp);
            VIENNACL_ERR_CHECK(err);
            assert(temp > 0 && bool("ViennaCL: FATAL error: Provided context does not contain any devices!"));
            num_devices = static_cast<cl_uint>(temp / sizeof(cl_device_id));

            #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
            std::cout << "ViennaCL: Reusing context with " << num_devices << " devices." << std::endl;
            #endif

            std::vector<cl_device_id> device_ids(num_devices);
            err = clGetContextInfo(h_.get(), CL_CONTEXT_DEVICES, num_devices * sizeof(cl_device_id), &(device_ids[0]), NULL);
            VIENNACL_ERR_CHECK(err);

            for (vcl_size_t i=0; i<num_devices; ++i)
              devices_.push_back(viennacl::ocl::device(device_ids[i]));
          }
          current_device_id_ = 0;

          initialized_ = true;
          #if defined(VIENNACL_DEBUG_ALL) || defined(VIENNACL_DEBUG_CONTEXT)
          std::cout << "ViennaCL: Initialization of ViennaCL context from existing context done." << std::endl;
          #endif
        }


        bool initialized_;
        cl_device_type device_type_;
        viennacl::ocl::handle<cl_context> h_;
        std::vector< viennacl::ocl::device > devices_;
        vcl_size_t current_device_id_;
        vcl_size_t default_device_num_;
        ProgramContainer programs_;
        std::map< cl_device_id, std::vector< viennacl::ocl::command_queue> > queues_;
        std::string build_options_;
        vcl_size_t pf_index_;
        vcl_size_t current_queue_id_;
    }; //context



    /** @brief Adds a kernel to the program */
    inline viennacl::ocl::kernel & viennacl::ocl::program::add_kernel(cl_kernel kernel_handle, std::string const & kernel_name)
    {
      assert(p_context_ != NULL && bool("Pointer to context invalid in viennacl::ocl::program object"));
      viennacl::ocl::kernel temp(kernel_handle, *this, *p_context_, kernel_name);
      kernels_.push_back(temp);
      return kernels_.back();
    }

    /** @brief Returns the kernel with the provided name */
    inline viennacl::ocl::kernel & viennacl::ocl::program::get_kernel(std::string const & name)
    {
      //std::cout << "Requiring kernel " << name << " from program " << name_ << std::endl;
      for (KernelContainer::iterator it = kernels_.begin();
            it != kernels_.end();
           ++it)
      {
        if (it->name() == name)
          return *it;
      }
      std::cerr << "ViennaCL: FATAL ERROR: Could not find kernel '" << name << "' from program '" << name_ << "'" << std::endl;
      std::cout << "Number of kernels in program: " << kernels_.size() << std::endl;
      throw "Kernel not found";
      //return kernels_[0];  //return a defined object
    }


    inline void viennacl::ocl::kernel::set_work_size_defaults()
    {
      assert( p_program_ != NULL && bool("Kernel not initialized, program pointer invalid."));
      assert( p_context_ != NULL && bool("Kernel not initialized, context pointer invalid."));

      if (   (p_context_->current_device().type() == CL_DEVICE_TYPE_GPU)
          || (p_context_->current_device().type() == CL_DEVICE_TYPE_ACCELERATOR) // Xeon Phi
         )
      {
        local_work_size_[0] = 128;      local_work_size_[1] = 0;  local_work_size_[2] = 0;
        global_work_size_[0] = 128*128; global_work_size_[1] = 0; global_work_size_[2] = 0;
      }
      else //assume CPU type:
      {
        //conservative assumption: one thread per CPU core:
        local_work_size_[0] = 1; local_work_size_[1] = 0; local_work_size_[2] = 0;

        size_type units = p_context_->current_device().max_compute_units();
        size_type s = 1;

        while (s < units) // find next power of 2. Important to make reductions work on e.g. six-core CPUs.
          s *= 2;

        global_work_size_[0] = s; global_work_size_[1] = 0; global_work_size_[2] = 0;
      }
    }

  }
}

#endif