public function getTotalDPU()
    {
        if ($this->_csdl === false) {
            throw new DataSift_Exception_InvalidData('Total DPU not available');
        }
        if ($this->_total_dpu === false) {
            // Catch any compilation errors so they don't pass up to the caller
            try {
                $this->validate();
            } catch (DataSift_Exception_CompileFailed $e) {
            }
        }
        return $this->_total_dpu;
    }