Parallel example for computing pi efficiently is actually slow

[rforcen]

i create countProcessors() (CP) threads each one of them processes a chunk of 
ch.len/CP size
    
    
    proc mt_pi(n: int): float =
      proc term(i,n:int, ch:var seq[float]) =
        let
          size = ch.len
          chunk_sz = size div n
          rfrom = i * chunk_sz
          rto = if (i+1) * chunk_sz > size: size else: (i+1) * chunk_sz
        
        for index in rfrom..<rto: # process in this thread a chunk
          ch[index] = 4 * math.pow(-1, index.float) / (2*index.float + 1)
      
      let nth = countProcessors()
      
      var ch = newSeq[float](n+1)
      
      parallel:
        for k in 0..nth:
          spawn term(k, nth, ch)
      
      for k in 0..ch.high: result += ch[k]
    
    
    Run