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+/ .* Improved

initial writing: 2009-05-01 last updated: 2009-06-07

x +/ .*y is now more efficient on vector and sparse matrix arguments. The following benchmarks illustrate the improvements in time and space.

sa=: 4 : 0  NB. random sparse array with density x and shape y
 m=. >.x**/y
 1$.y;(i.#y);0;((m,#y)?@$y);65536%~_5e8+m ?@$ 1e9
)

ts=: 6!:2 , 7!:2@]  NB. time and space

x=. d sa 2$n
y=. d sa 2$n
ts 'x +/ .* y'

d		n		J 7.01				J 6.02				Ratio
0.01		200		0.000479		2.60480e4		0.012485		5.57312e5		26.06		21.40
0.01		400		0.003083		2.09344e5		0.092145		3.89229e6		29.89		18.59
0.01		800		0.008078		1.59162e6		0.628309		3.01444e7		77.78		18.94
0.01		1600		0.053682		1.26232e7		4.999638		2.36795e8		93.13		18.76
0.1		200		0.008470		1.58342e6		0.118047		6.44698e6		13.94		4.07
0.1		400		0.042008		6.30714e6		0.853741		3.86877e7		20.32		6.13
0.1		800		0.084491		2.51917e7		7.353612		2.59295e8		87.03		10.29
0.1		1600		0.499803		1.00714e8		out of memory				-		-

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