agent elevator writes: In 2010, Saudi Arabia hosted an international design competition aimed at safely accommodating more pilgrims at Mecca's Grand Mosque. One of the participants told IEEE Spectrum that the crowd densities there (6 people per square meter) bogged down off-the-shelf software so badly that simulation run times were about 10 to 20 times slower than real time crowd movement. Nevertheless, he found some workarounds that gave designers a plan to double the Grand Mosque's peak visitor rate from 40,000 to 102,000 people per hour. Last week's stampede took place well away from the mosque, but signals sent to pilgrims telling them when to speed up or slow down could help prevent such a tragedy, the crowd simulation expert said. Other engineers are turning to fuzzy logic as way to predict how crowds will react in a panic.