pirand.knucpp

/******************************************************************************
  Copyright 2016 KNUPATH
  All rights reserved.
  KNUPATH Proprietary and Confidential

  File: pirand.knucpp

  Description: Kernel code for KPI pi estimation example

******************************************************************************/

#include "kpi/kpi_kernel.h"

const float        R         = 1.0;
const unsigned int RAND_MASK = 0x00ffffff;
const float        maxRand   = (float) RAND_MASK;

float getRandCoord()
{
    float randNum = (float) (KPI_Rand() & RAND_MASK);
    float coord = (randNum / maxRand * 2.0 * R) - R;
    return coord;
}

bool isInCircle(float x, float y)
{
    float dist = __builtin_knureon_fsqrt((x * x) + (y * y));
    return (dist <= R);
}

// Generate random points within a square and find the ratio of points
// which fall within an inscribed circle
extern "C" __knu_kernel
void piRandRatio(int coordsPerRank)
{
    const int RANK       = KPI_Rank();
    int WORLD_SIZE = KPI_World_Size();

    // Each rank needs a different rand seed
    KPI_Srand(0x314159 * RANK, 0x314159 * 2 * RANK, 0x314159 * 3 * RANK);

    int numInCircle = 0;
    int numCoords;

    for (numCoords = 0; numCoords < coordsPerRank; numCoords++)
    {
        // Generate random coordinates within square
        float x = getRandCoord();
        float y = getRandCoord();

        // Count the number of coordinates within an inscribed circle
        if (isInCircle(x, y))
        {
            numInCircle++;
        }
    }

    if(0 != RANK)
    {
        // All tDSPs except RANK 0 will send the ratio of coordinates
        // within the circle to the "aggregator" at RANK 0
        float ratioInCircle = (float) numInCircle / (float) coordsPerRank;
        // Send the ratio to rank 0
        KPI_Send(&ratioInCircle, 1, 0);
    }
    else
    {
        // RANK 0 will collect data from the other tDSPs and send the
        // result to the host.
        float     aggRatioInCircle = 0.0f;

        // Sum up the resulting ratios of points inside the circle
        for (int i = 1; i < WORLD_SIZE; i++)
        {
            float ratioInCircle;
            KPI_Recv(&ratioInCircle, 1);
            aggRatioInCircle += ratioInCircle;
        }

        // Calculate average ratio of points inside the circle
        aggRatioInCircle /= (float) (WORLD_SIZE - 1);

        // Estimate pi = 4 * (points inside circle) / (total points)
        float pi = aggRatioInCircle * 4.0;

        // Send result to host
        KPI_Send_Host(&pi, sizeof(pi)/4, 0);

        // Send World Size
        KPI_Send_Host(&WORLD_SIZE, 1, 0);
    }
}