TY - GEN

T1 - On read-once vs. multiple access to randomness in logspace

AU - Nisan, Noam

PY - 1990

Y1 - 1990

N2 - In the correct definition of randomized space-bounded computation, the machine has access to a random coin. The coin can be flipped at will, but outcomes of previous coin flips cannot be recalled unless they are saved in the machine's limited memory. In contrast to this read-once mechanism of accessing the random source, one may consider Turing machines which have access to a random tape. Here, the random bits may be multiply accessed by the machine. The author demonstrates a very concrete sense in which multiple access to the random bits is better than read-once access to them: Every language accepted with bounded two-sided error by a read-once-randomized logspace machine can be accepted with zero error by a randomized logspace machine having multiple access to the random bits.

AB - In the correct definition of randomized space-bounded computation, the machine has access to a random coin. The coin can be flipped at will, but outcomes of previous coin flips cannot be recalled unless they are saved in the machine's limited memory. In contrast to this read-once mechanism of accessing the random source, one may consider Turing machines which have access to a random tape. Here, the random bits may be multiply accessed by the machine. The author demonstrates a very concrete sense in which multiple access to the random bits is better than read-once access to them: Every language accepted with bounded two-sided error by a read-once-randomized logspace machine can be accepted with zero error by a randomized logspace machine having multiple access to the random bits.

UR - http://www.scopus.com/inward/record.url?scp=0025661863&partnerID=8YFLogxK

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AN - SCOPUS:0025661863

SN - 0818620722

T3 - Proc Fifth Annu Struct Complexity Theor

SP - 179

EP - 184

BT - Proc Fifth Annu Struct Complexity Theor

PB - Publ by IEEE

T2 - Proceedings of the Fifth Annual Structure in Complexity Theory Conference

Y2 - 8 July 1990 through 11 July 1990

ER -