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The Lamport timestamp algorithm is a simple logical clock algorithm used to determine the order of events in a distributed computer system.As different nodes or processes will typically not be perfectly synchronized, this algorithm is used to provide a partial ordering of events with minimal overhead, and conceptually provide a starting point for the more advanced vector clock method.
Common examples of this type of timestamp are a postmark on a letter or the "in" and "out" times on a time card. With the advent of digital data systems, the term has expanded to refer to digital date and time information attached to digital data.
Just as in Lamport timestamps, inter-process messages contain the state of the sending process's logical clock. A vector clock of a system of N processes is an array /vector of N logical clocks, one clock per process; a local "largest possible values" copy of the global clock-array is kept in each process.
This algorithm creates 3(N − 1) messages per request, or (N − 1) messages and 2 broadcasts. 3(N − 1) messages per request includes: (N − 1) total number of requests (N − 1) total number of replies (N − 1) total number of releases
If the resolution of the timestamp is too large (coarse), the possibility of two or more timestamps being equal is increased and thus enabling some transactions to commit out of correct order. For example, for a system that creates one hundred unique timestamps per second, two events that occur 2 milliseconds apart may be given the same ...
Command or function Resolution Epoch or range Android: java.lang.System.currentTimeMillis() 1 ms 1 January 1970 BIOS INT 1Ah, AH=00h [1] 54.9254 ms 18.2065 Hz Midnight of the current day INT 1Ah, AH=02h [2] 1 s Midnight of the current day INT 1Ah, AH=04h [3] 1 day 1 January 1980 to 31 December 1999 or 31 December 2079 (system dependent) CP/M Plus
For example, 00:00:00 UTC on 1 January 1971 is represented in Unix time as 31 536 000. Negative values, on systems that support them, indicate times before the Unix epoch, with the value decreasing by 1 for every non-leap second before the epoch. For example, 00:00:00 UTC on 1 January 1969 is represented in Unix time as −31 536 000.
[1] A transport stream may contain multiple programs and each program may have its own time base. The time bases of different programs within a transport stream may be different. Because PTSs apply to the decoding of individual elementary streams, they reside in the PES packet layer of both the transport streams and program streams. End-to-end ...