Commit 291480a1 authored by Tomáš Oberhuber's avatar Tomáš Oberhuber
Browse files

Writting segmented scan tutorial.

parent 263bebcc

Documentation/Tutorials/ReductionAndScan/CMakeLists.txt

+6 −3
Original line number Diff line number Diff line
@@ -23,6 +23,8 @@ IF( BUILD_CUDA ) 
   ADD_CUSTOM_COMMAND( COMMAND ScanExample > ScanExample.out OUTPUT ScanExample.out )

   CUDA_ADD_EXECUTABLE( ExclusiveScanExample ExclusiveScanExample.cu )

   ADD_CUSTOM_COMMAND( COMMAND ExclusiveScanExample > ExclusiveScanExample.out OUTPUT ExclusiveScanExample.out )

   CUDA_ADD_EXECUTABLE( SegmentedScanExample SegmentedScanExample.cu )

   ADD_CUSTOM_COMMAND( COMMAND SegmentedScanExample > SegmentedScanExample.out OUTPUT SegmentedScanExample.out )

ENDIF()



IF( BUILD_CUDA )
@@ -38,5 +40,6 @@ ADD_CUSTOM_TARGET( TutorialsReduction-cuda ALL DEPENDS 
   MapReduceExample-3.out

   ReductionWithArgument.out

   ScanExample.out

   ExclusiveScanExample.out )

   ExclusiveScanExample.out

   SegmentedScanExample.out )

ENDIF()

Documentation/Tutorials/ReductionAndScan/SegmentedScanExample.cpp

+15 −13
Original line number Diff line number Diff line
@@ -11,7 +11,7 @@ using namespace TNL::Containers; 
using namespace TNL::Containers::Algorithms;



template< typename Device >

void scan( Vector< double, Device >& v )

void segmentedScan( Vector< double, Device >& v, Vector< bool, Device >& flags )

{

   /***

    * Reduction is sum of two numbers.
@@ -23,29 +23,31 @@ void scan( Vector< double, Device >& v ) 
    * where the scan is performed, lambda function which is used by the scan and

    * zero element (idempotent) of the 'sum' operation.

    */

   Scan< Device >::perform( v, 0, v.getSize(), reduce, 0.0 );

   SegmentedScan< Device >::perform( v, flags, 0, v.getSize(), reduce, 0.0 );

}



int main( int argc, char* argv[] )

{

   /***

    * Firstly, test the prefix sum with vectors allocated on CPU.

    * Firstly, test the segmented prefix sum with vectors allocated on CPU.

    */

   Vector< double, Devices::Host > host_v( 10 );

   host_v = 1.0;

   Vector< bool, Devices::Host > host_flags{ 1,0,0,1,0,0,0,1,0,1,0,0, 0, 0 };

   Vector< double, Devices::Host > host_v { 1,3,5,2,4,6,9,3,5,3,6,9,12,15 };

   std::cout << "host_flags = " << host_flags << std::endl;

   std::cout << "host_v     = " << host_v << std::endl;

   scan( host_v );

   std::cout << "The prefix sum of the host vector is " << host_v << "." << std::endl;

   segmentedScan( host_v, host_flags );

   std::cout << "The segmented prefix sum of the host vector is " << host_v << "." << std::endl;



   /***

    * And then also on GPU.

    */

#ifdef HAVE_CUDA

   Vector< double, Devices::Cuda > cuda_v( 10 );

   cuda_v = 1.0;

   std::cout << "cuda_v = " << cuda_v << std::endl;

   scan( cuda_v );

   std::cout << "The prefix sum of the CUDA vector is " << cuda_v << "." << std::endl;

   //Vector< bool, Devices::Cuda > cuda_flags{ 1,0,0,1,0,0,0,1,0,1,0,0, 0, 0 };

   //Vector< double, Devices::Cuda > cuda_v { 1,3,5,2,4,6,9,3,5,3,6,9,12,15 };

   //std::cout << "cuda_flags = " << cuda_flags << std::endl;

   //std::cout << "cuda_v     = " << cuda_v << std::endl;

   //segmentedScan( cuda_v, cuda_flags );

   //std::cout << "The segmnted prefix sum of the CUDA vector is " << cuda_v << "." << std::endl;

#endif

   return EXIT_SUCCESS;

}

Documentation/Tutorials/ReductionAndScan/tutorial_03_ReductionAndScan.md

+6 −0
Original line number Diff line number Diff line
@@ -251,4 +251,10 @@ In addition to common scan, we need to encode the segments of the input sequence 
[1,0,0,1,0,0,0,1,0,1,0,0, 0, 0]

[1,3,5,2,4,6,9,3,5,3,6,9,12,15]

```

**Note: Segmented scan is not implemented for CUDA yet.**



\include SegmentedScanExample.cpp



The result reads as:



\include SegmentedScanExample.out