// Compile with gcc: 
//   gcc -pg profiletest3.c -oprofiletest3 -lm

#include <stdio.h>
#include <math.h>

// Global variables 

double *data;      // The data.
int N;             // Size of the data.
int numTrials;     // Number of trials to use in estimation.
int *max;          // Store partial maxima.


// Random-number generator

static r_seed = 12345678L;

double uniform ()
{
  static long m = 2147483647;
  static long a = 48271;
  static long q = 44488;
  static long r = 3399;
  long t, lo, hi;

  hi = r_seed / q;
  lo = r_seed - q * hi;
  t = a * lo - r * hi;
  if (t > 0)
    r_seed = t;
  else
    r_seed = t + m;
  return ( (double) r_seed / (double) m );

}

// Build random array

double* makeRandomArray (int length)
{
  int i;

  double *A = (double*) malloc (sizeof(double) * length);
  for (i=0; i<length; i++) {
    A[i] = floor (length*uniform ());
  }
  return A;
}


// Find partial maximum: the max value in data[0],...,data[limit].

int findMax (int limit)
{
  return max[limit];
}

void preComputeMax ()
{
  int limit, i;
  double m;

  max = (int*) malloc (sizeof(int) * N);

  m = data[0];
  for (i=1; i<N; i++) {
    if (data[i] > m)
      m = data[i];
    max[i] = m;
  }

}


// Find partial sum: the sum of data[0],...,data[limit].

double findSum (int limit)
{
  int k;
  double sum;

  sum = 0;
  for (k=0; k<limit; k++)
    sum += data[k];
  return sum;
}


void estimateMax ()
{
  double total, avg;
  int n, value, limit;

  // 1. Maintain total.
  total = 0;

  // 2. Repeat numTrials times.
  for (n=0; n<numTrials; n++) {

    // 2.1 Pick a sub-array randomly.
    limit = floor (N*uniform());

    // 2.2 Compute partial max.
    value = findMax (limit);

    // 2.3 Accumulate.
    total += value;
  }

  // 3. Compute average.
  avg = total / (double) numTrials;

  // 4. Output.
  printf ("Estimate of maximum=%lf\n", avg);
}


void estimateSum ()
{
  double total, avg;
  int n, value, limit;

  // 1. Maintain total.
  total = 0;

  // 2. Repeat numTrials times.
  for (n=0; n<numTrials; n++) {

    // 2.1 Pick a sub-array randomly.
    limit = floor (N*uniform());

    // 2.2 Compute partial sum.
    value = findSum (limit);

    // 2.3 Accumulate.
    total += value;
  }

  // 3. Compute average.
  avg = total / (double) numTrials;

  // 4. Output.
  printf ("Estimate of sum=%lf\n", avg);
}

int main ()
{
  // Set data size and number of trials.
  N = 1000;
  numTrials = 100000;

  // Create random data.
  data = makeRandomArray (N);

  // Precompute
  preComputeMax();

  // Estimate the average partial-maximum.
  estimateMax();

  // Estimate the average partial-sum.
  estimateSum();
}