The heating packet of the present invention comprises an air-permeable bag containing a heat-generating composition or a sheet-like heat-generating body which generates heat upon contacting oxygen in air. One illustrative embodiment includes a first watchdog timer internal to the microprocessor and a second watchdog timer external to the microprocessor. The program code testing system determines accesses of architectural structures made by the two or more threads of the multi-threaded program code and uses the determined accesses to determine a time for which the program code is exposed to soft errors. or above; and an energy storage density of at least 15 Jcc.