Help / Release / J 5.03 / (+/ % #)\ Improved

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(+/ % #)\ Improved

initial writing: 2003-11-10 last updated: 2003-12-04

The dyad (+/ % #)\ computes the moving average and is now implemented by special code for positive left arguments and integer and floating point right arguments. The following table illustrates the improvements in time and space.

x=: 0.01*?n$1000
ts=: 6!:2 , 7!:2@]  NB. time and space
ts 'm (+/ % #)\x'

m		n		J 5.03			J 5.02			Ratio
50		1e5		0.010857	1.051264e6		0.428732	3.148352e6		39.49		2.99
50		2e5		0.021686	2.099840e6		0.855940	6.294080e6		39.47		3.00
50		4e5		0.047796	4.196992e6		1.693698	1.258554e7		35.44		3.00
50		8e5		0.097144	8.391296e6		3.408151	2.516845e7		35.08		3.00
100		1e5		0.011251	1.051264e6		0.467502	3.148864e6		41.55		3.00
100		2e5		0.022939	2.099840e6		0.920847	6.294592e6		40.14		3.00
100		4e5		0.044595	4.196992e6		1.843981	1.258605e7		41.35		3.00
100		8e5		0.092017	8.391296e6		3.680761	2.516896e7		40.00		3.00
200		1e5		0.011448	1.051264e6		0.625874	3.149888e6		54.67		3.00
200		2e5		0.022340	2.099840e6		1.255497	6.295616e6		56.20		3.00
200		4e5		0.045064	4.196992e6		2.504865	1.258707e7		55.58		3.00
200		8e5		0.089157	8.391296e6		5.023058	2.516998e7		56.34		3.00
400		1e5		0.011027	1.051264e6		0.776791	3.151936e6		70.45		3.00
400		2e5		0.022462	2.099840e6		1.565228	6.297664e6		69.68		3.00
400		4e5		0.047861	4.196992e6		3.124304	1.258912e7		65.28		3.00
400		8e5		0.091099	8.391296e6		6.275170	2.517203e7		68.88		3.00

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