MultiThreaded.h

#ifndef MANTID_KERNEL_MULTITHREADED_H_
#define MANTID_KERNEL_MULTITHREADED_H_

// _OPENMP is automatically defined if openMP support is enabled in the compiler.
#ifdef _OPENMP

// The syntax used to dfine a pragma within a macro is different on windows and GCC
#ifdef _MSC_VER 
#define PRAGMA __pragma
#else //_MSC_VER 
#define PRAGMA(x) _Pragma(#x)
#endif //_MSC_VER 

#include <omp.h>

/** Includes code to add OpenMP commands to run the next for loop in parallel.
*   This includes an arbirary check: condition.
*   "condition" must evaluate to TRUE in order for the
*   code to be executed in parallel
*/
#define PARALLEL_FOR_IF(condition) \
    PRAGMA(omp parallel for if (condition) )

/** Includes code to add OpenMP commands to run the next for loop in parallel.
*   This includes no checks to see if workspaces are suitable
*   and therefore should not be used in any loops that access workspaces.
*/
#define PARALLEL_FOR_NO_WSP_CHECK() \
    PRAGMA(omp parallel for)

/** Includes code to add OpenMP commands to run the next for loop in parallel.
*		The workspace is checked to ensure it is suitable for multithreaded access.
*/
#define PARALLEL_FOR1(workspace1) \
		PRAGMA(omp parallel for if (workspace1->threadSafe()))

/** Includes code to add OpenMP commands to run the next for loop in parallel.
*	 Both workspaces are checked to ensure they suitable for multithreaded access.
*/
#define PARALLEL_FOR2(workspace1, workspace2) \
		PRAGMA(omp parallel for if (workspace1->threadSafe() && workspace2->threadSafe()))

/** Includes code to add OpenMP commands to run the next for loop in parallel.
*	 All three workspaces are checked to ensure they suitable for multithreaded access.
*/
#define PARALLEL_FOR3(workspace1, workspace2, workspace3) \
                PRAGMA(omp parallel for if (workspace1->threadSafe() && workspace2->threadSafe() && workspace3->threadSafe()))

/** Ensures that the next execution line or block is only executed if
* there are multple threads execting in this region
*/
#define IF_PARALLEL \
                if (omp_get_num_threads() > 1)

/** Ensures that the next execution line or block is only executed if
* there is only one thread in operation
*/
#define IF_NOT_PARALLEL \
                if (omp_get_num_threads() == 1)

/** Begins a block to skip processing is the algorithm has been interupted
* Note the end of the block if not defined that must be added by including 
* PARALLEL_END_INTERUPT_REGION at the end of the loop
*/
#define PARALLEL_START_INTERUPT_REGION \
                if (!m_parallelException && !m_cancel) { \
                  try {

/** Ends a block to skip processing is the algorithm has been interupted
* Note the start of the block if not defined that must be added by including 
* PARALLEL_START_INTERUPT_REGION at the start of the loop
*/
#define PARALLEL_END_INTERUPT_REGION \
                  } /* End of try block in PARALLEL_START_INTERUPT_REGION */ \
                  catch(std::exception &ex) { \
                    if (!m_parallelException) \
                    { \
                      m_parallelException = true; \
                      g_log.error() << this->name() << ": " << ex.what() << "\n"; \
                    } \
                  } \
                  catch(...) { m_parallelException = true; } \
                } // End of if block in PARALLEL_START_INTERUPT_REGION

/** Adds a check after a Parallel region to see if it was interupted
*/
#define PARALLEL_CHECK_INTERUPT_REGION \
                if (m_parallelException) \
                { \
                  g_log.debug("Exception thrown in parallel region"); \
                  throw std::runtime_error(this->name()+": error (see log)"); \
                } \
                interruption_point();

/** Specifies that the next code line or block will only allow one thread through at a time
*/
#define PARALLEL_CRITICAL(name) \
                PRAGMA(omp critical(name))

/** Allows only one thread at a time to write to a specific memory location
 */
#define PARALLEL_ATOMIC \
                PRAGMA(omp atomic)

#define PARALLEL_THREAD_NUMBER omp_get_thread_num()

#define PARALLEL \
                PRAGMA(omp parallel)

#define PARALLEL_SECTIONS \
                PRAGMA(omp sections nowait)

#define PARALLEL_SECTION \
                PRAGMA(omp section)

#else //_OPENMP
///Empty definitions - to enable set your complier to enable openMP
#define PARALLEL_FOR_IF(condition)
#define PARALLEL_FOR_NO_WSP_CHECK()
#define PARALLEL_FOR1(workspace1)
#define PARALLEL_FOR2(workspace1, workspace2)
#define PARALLEL_FOR3(workspace1, workspace2, workspace3)
#define IF_PARALLEL if (false)
#define IF_NOT_PARALLEL
#define PARALLEL_START_INTERUPT_REGION
#define PARALLEL_END_INTERUPT_REGION
#define PARALLEL_CHECK_INTERUPT_REGION
#define PARALLEL_CRITICAL(name)
#define PARALLEL_ATOMIC
#define PARALLEL_THREAD_NUMBER 0
#define PARALLEL
#define PARALLEL_SECTIONS
#define PARALLEL_SECTION
#endif //_OPENMP

#endif //MANTID_KERNEL_MULTITHREADED_H_