The class P, typically taken to consist of all the "tractable" problems for a sequential computer, contains the class NC, which consists of those problems which can be efficiently solved on a parallel computer. This is because parallel computers can be simulated on a sequential machine. It is not known whether NC = P. In other words, it is not known whether there are any tractable problems that are inherently sequential. Just as it is widely suspected that P does not equal NP, so it is widely suspected that NC does not equal P.
The class P typically taken to consist of all the "tractable" problems for a sequential computer contains the class NC which consists of those problems which can be efficiently solved on a parallel computer This is because parallel computers can be simulated on a sequential machine It is not known whether NC = P In other words it is not known whether there are any tractable problems that are inherently sequential Just as it is widely suspected that P does not equal NP so it is widely suspected that NC does not equal P