Module: DarvinFunctions

Defined in:
ext/darvin_functions.c

Class Method Summary collapse

Class Method Details

.nkmax(varray) ⇒ Object

vself is a reference to the module or itself

varray is a Ruby array



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# File 'ext/darvin_functions.c', line 17

VALUE mDarvinFunctions_nkmax(VALUE vself, VALUE varray) {
  VALUE new_array;
  int  i, j, trail, offset;
  long  *tot;                                    // total for specific interval
  long  *maxTot;                               // current sum for (i-1)

  (void)vself;                                  // silence unused variable warning message

  if (NIL_P(varray) || RARRAY_LEN(varray) == 0)
    return varray;

  new_array = rb_ary_new2(RARRAY_LEN(varray));

  tot = ALLOCA_N(long, RARRAY_LEN(varray));      // allocate memory
  maxTot = ALLOCA_N(long, RARRAY_LEN(varray)); // allocate memory

  trail = 0;                                   // trailing value
  
  maxTot[0] = tot[0] = FIX2INT(RARRAY_PTR(varray)[0]);               // need first total (for single cell average), seed for others

  /*
   * this loop initializes the totals for all slot averages (1-n)
   * assume numbers are 1 2 3 4 5
   * maxTot[] will be 1, 3, 6, 10, 15
   * The idea is each slot is initialized to the earliers total values, 
   * that is slot0 is initialized to 1
   *         slot1 is initialized to 1 + 2
   *         ...
   *         slot4 is initialized to 1 + 2 + 3 + 4 + 5
   */
  for (i=1; i<RARRAY_LEN(varray); i++)                                 // loop thru all the numbers
    maxTot[i] = tot[i] = (tot[i-1] + FIX2INT(RARRAY_PTR(varray)[i])); // compute tot for subsequent cells (starting at cell 0)

  for (offset=1; offset<RARRAY_LEN(varray); offset++) {                // loop starting at index 1 (index-1 is the value to subtract)
    trail = FIX2INT(RARRAY_PTR(varray)[offset-1]);                    // this is the value to subtract from the beginning of the list
    
    for (i=offset; i<RARRAY_LEN(varray); i++) {                       // first time subtract 1 from all (except n list)
      j = i - offset;                                                  // subtract trail and add next value
      tot[j] += (FIX2INT(RARRAY_PTR(varray)[i]) - trail);              // to temp variable
      if (tot[j] > maxTot[j]) maxTot[j] = tot[j];                     // set maxTot for slot if larger
    }
  }
  
  for (i=0; i<RARRAY_LEN(varray); i++) {
    rb_ary_push(new_array, INT2FIX(roundNumber((double)maxTot[i] / (double)(i+1))));
  }

  return new_array;
}