A reader-writer lock minimizes writer and reader overhead by employing lock structures that are shared among groups of processors that have lower latencies. The pin includes a cylindrical body having a vertical notch, a pair of symmetrically opposite latches depending from the cylindrical body to enable the pin to elastically deform, and a pair of barbs extending outwardly and slightly upwardly from bottom ends of the latches respectively. Otherwise, if single-error words on a page contain erased and programmed bit errors, then a refresh operation, consisting of an erase and program, takes place. Adaptive compression also allows for anomalous conditions such as out-of-range data values to be handled gracefully. The optical device projects a light beam, and breaking the beam with a gesture signals the response. By irradiation of the laser beam on the thermoelectromotive force generator, it is possible to detect a short-circuit defect, which lies between the first-layer wires.