Subject: [boost] [parameter] Compile-time performance
From: Domagoj Saric (domagoj.saric_at_[hidden])
Date: 2011-02-25 07:58:48
I have an in-house framework a part of which is very similar to
Boost.Parameter so I tried to refactor it to use Boost.Parameter and,
unfortunately, noticed a big compile-time hit (the project has a very large
number instantiations of class templates with 'named non-type template
With my code (and MSVC++ 10) build time was ~56 seconds with a maximum
cl.exe memory allocation size of ~720 MB. After switching to Boost.Parameter
build time whent to ~2:24 seconds with a maximum cl.exe memory allocation
size of ~815 MB.
The most likely suspect is the usage of a forward-sequence for parameter
type storage (argument packs) from which you fetch passed parameters using
key-based lookup with the value_type<> metafunction. In my code I use an
associative container (mpl::map) for the task which has a
'natural'/'efficient' key-based lookup...
To confirm this I minimally changed the Boost.Parameter-based version of my
code only to use mpl::maps instead of Boost.Parameter ArgumentPacks and
built time fell to ~58 seconds...(true, this does not have all the
compile-time check for correct usage and concept validation that
ParameterSpecs and ArgumentPacks have but I'd expect this to have a much
smaller effect than key-based lookup on a forward sequence)...
Is there an inherent issue that forbids the use of an associative container
for ArgumentPacks or can this be fixed?
-- "What Huxley teaches is that in the age of advanced technology, spiritual devastation is more likely to come from an enemy with a smiling face than from one whose countenance exudes suspicion and hate." Neil Postman
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