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Re: fast summing alternative?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg128377] Re: fast summing alternative?
  • From: Ray Koopman <koopman at sfu.ca>
  • Date: Thu, 11 Oct 2012 02:08:07 -0400 (EDT)
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On Oct 9, 10:34 pm, Ray Koopman <koop... at sfu.ca> wrote:
> On Oct 8, 9:48 pm, Ray Koopman <koop... at sfu.ca> wrote:> On Oct 7, 11:59
>>
>> tab2 = Transpose @ With[{negnewMat = - newMat}, MapThread[
>>        Dot, {weights, UnitStep[# + negnewMat]} ]& /@ sortMat ]
>
> This should be faster:
>
> tab3 = Transpose[ MapThread[Dot,{weights,#}]& /@ Partition[
>        UnitStep[Plus@@Transpose@Tuples@{sortMat,-newMat}], bNum] ]

This may be marginally faster yet:

tab4 = Transpose@Developer`PartitionMap[ MapThread[Dot,{weights,#}]&,
       UnitStep[Plus@@Transpose@Tuples@{sortMat,-newMat}], bNum]



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