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en:group:seminars:20110722 [2011/07/18 10:45] maatouk |
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| ==== abstract ==== | ==== abstract ==== | ||
| - | TBA | + | We prove a time-space tradeoff lower bound of T = Omega(n log(n/S) log log(n/S)) for randomized oblivious branching programs to compute 1GAP, also known as the pointer jumping problem, a problem for which there is a simple deterministic time n and space O(log n) RAM (random access machine) algorithm. |
| + | We give a similar time-space tradeoff of T = Omega(n log(n/S) log log(n/S)) for | ||
| + | Boolean randomized oblivious branching programs computing GIP-MAP, a variation of the generalized inner product problem that can be computed in time n and space O(\og^2 n) by a | ||
| + | deterministic Boolean branching program. | ||
| + | |||
| + | These are also the first lower bounds for randomized oblivious branching programs computing explicit functions that apply for T=omega(n log n). They also show that any simulation of general branching programs by randomized oblivious ones requires either | ||
| + | a superlogarithmic increase in time or an exponential increase in space. | ||