Functions computable in polynomial space
Consider nondeterministic polynomial- time Turing machine that on input x outputs a 3 × 3 matrix with entries from {−1, 0, 1} on each of its paths. Define the function f where f ( x) is the upper left entry in the product of all these matrices (in an order of the paths to be made precise below). We...
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| Published in: | Information and computation Vol. 198; no. 1; pp. 56 - 70 |
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| Main Authors: | , |
| Format: | Journal Article |
| Language: | English |
| Published: |
San Diego, CA
Elsevier Inc
10.04.2005
Elsevier |
| Subjects: | |
| ISSN: | 0890-5401, 1090-2651 |
| Online Access: | Get full text |
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| Summary: | Consider nondeterministic polynomial-
time Turing machine that on input
x outputs a 3
×
3 matrix with entries from {−1,
0,
1} on each of its paths. Define the function
f where
f
(
x) is the upper left entry in the product of all these matrices (in an order of the paths to be made precise below). We show that the class of functions
f computable as just described is exactly the class FPSPACE of integer-valued functions computable by polynomial-space Turing machines. Along the way we obtain characterizations of FPSPACE in terms of arithmetic circuits and straight-line programs. |
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| ISSN: | 0890-5401 1090-2651 |
| DOI: | 10.1016/j.ic.2005.02.002 |