Computational complexity of matrix multiplication: Difference between revisions

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m Capitalising short description "algorithmic runtime requirements for matrix multiplication" per WP:SDFORMAT (via Bandersnatch)
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=== Lower bounds for ω ===
 
There is a trivial lower bound of {{tmath|\omega \ge 2}}. Since any algorithm for multiplying two {{math|''n'' × ''n''}}-matrices has to process all {{math|2''n''<sup>2</sup>}} entries, there is a trivial asymptotic lower bound of {{math|Ω(''n''<sup>2</sup>)}} operations for any matrix multiplication algorithm. Thus {{tmath|2\le \omega < 2.373}}. It is unknown whether {{tmath|\omega > 2}}. The best known lower bound for matrix-multiplication complexity is {{math|Ω(''n''<sup>2</sup> log(''n''))}}, for bounded coefficient [[Arithmetic circuit complexity|arithmetic circuits]] over the real or complex numbers, and is due to [[Ran Raz]].<ref>{{cite journal | last1 = Raz | first1 = Ran | author-link = Ran Raz | year = 2002| title = On the complexity of matrix product | journal = Proceedings of the Thirty-fourthFourth Annual ACM Symposium on Theory of Computing | pages = 144 | doi = 10.1145/509907.509932 | isbn = 1581134959 | s2cid = 9582328 }}</ref>
 
=== Rectangular matrix multiplication ===