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Section: 29.8.4 [inner.product] Status: Resolved Submitter: United States Opened: 2017-02-03 Last modified: 2017-05-31
Priority: Not Prioritized
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Discussion:Addresses US 161
There is a surprising sequential operation applying BinaryOp1 in inner_product that may, for example, require additional storage for the parallel algorithms to enable effective distribution of work, and is likely to be a performance bottleneck. GENERALIZED_SUM is probably intended here for the parallel version of the algorithm, with the corresponding strengthening on constraints on BinaryOp1 to allow arbitrary order of evaluation.
Proposed change: For the overloads taking an execution policy, copy the current specification, but replace algorithm in Effects with
GENERALIZED_SUM(plus<>(), init, multiplies<>(*i1, *i2), ...) GENERALIZED_SUM(binary_op1, init, binary_op2(*i1, *i2), ...)
Resolved by P0623R0.