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MathGroup Archive 1992

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Determinant Function (Final Version?)

  • To: mathgroup <mathgroup at yoda.physics.unc.edu>
  • Subject: Determinant Function (Final Version?)
  • From: HAY at leicester.ac.uk
  • Date: Sun, 19 APR 92 13:30:13 GMT

Still faster(and simpler): The latest moral seems to be to work on structures as
directly as possible. But why didn't I see this before! 

NewDet3[M_] := 
	Plus@@Times@@(
		Append[Transpose[Transpose[#,{1,2,2}]],Signature/@#]&@
		Permutations[M]
	)

Timings (MacIIfx, Mma V 2.0):

a[n_] := Table[ StringJoin["a",ToString[i],ToString[j]], {i,1,n},{j,1,n}]

Do[ Print[ First[ Timing[ NewDet3[ a[n]]]]], {n,1,7}]

0.0666667 Second
0.0666667 Second
0.116667 Second
0.266667 Second
0.75 Second
4.1 Second
30.95 Second

Timings for NewDet2 were

0.0666667 Second
0.0833333 Second
0.133333 Second
0.283333 Second
0.933333 Second
5.13333 Second
38.1833 Second


Apologies for the long development period.

From
Allan Hayes
Department of Mathematics
The University
Leicester LE1 7RH
U.K.
hay at leicester.ac.uk





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