Since objects aren't addressable by default, there wouldn't be the problems with a bit-packed Boolean collection that C++'s "vector<bool>" has. Does "[Bool]" currently have the option of packed optimization, or would it have to be added via a proposal? Or does it have to be a separate type instead?
This also brings to mind bit fields and fixed-sized bit sets, but those might have to wait for value-based generic parameters, and that's at least until Swift 4....
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It has to be a separate “bitvector” type.
FWIW, C++’s vector<bool> optimization is widely considered to be a bad idea, and many people have talked about trying to remove it from the C++ standard entirely.
-Chris
On Jul 3, 2016, at 2:42 PM, Daryle Walker via swift-evolution <swift-evolution@swift.org> wrote:
Since objects aren't addressable by default, there wouldn't be the problems with a bit-packed Boolean collection that C++'s "vector<bool>" has. Does "[Bool]" currently have the option of packed optimization, or would it have to be added via a proposal? Or does it have to be a separate type instead?
As an additive thing, probably not much chance of seeing it in Swift 3,
then?
I tried wrapping CFBitVector just the other day but found performance to be
rather lacking for a number of operations because CF doesn't expose the
underlying storage. It would be nice to have something in the stdlib and
I'd be happy to contribute to proposal and/or implementation.
On Sun, Jul 3, 2016 at 17:45 Chris Lattner via swift-evolution < swift-evolution@swift.org> wrote:
> On Jul 3, 2016, at 2:42 PM, Daryle Walker via swift-evolution < > swift-evolution@swift.org> wrote:
>
> Since objects aren't addressable by default, there wouldn't be the
problems with a bit-packed Boolean collection that C++'s "vector<bool>"
has. Does "[Bool]" currently have the option of packed optimization, or
would it have to be added via a proposal? Or does it have to be a
separate type instead?It has to be a separate “bitvector” type.
FWIW, C++’s vector<bool> optimization is widely considered to be a bad
idea, and many people have talked about trying to remove it from the C++
standard entirely.-Chris
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AFAIK, the problem lies within the vector<bool> implementation. Other bit-packed implementations (e.g. boost:dynamic_bitset) are much more efficient. In certain cases, there are performance advantages to the bit packed representation as it is more cache-friendly.
That said, I don’t think that such specialised data structures should be part of the standard library. I’d leave this to a third-party solution.
— Taras
On 04 Jul 2016, at 00:44, Chris Lattner via swift-evolution <swift-evolution@swift.org> wrote:
On Jul 3, 2016, at 2:42 PM, Daryle Walker via swift-evolution <swift-evolution@swift.org> wrote:
Since objects aren't addressable by default, there wouldn't be the problems with a bit-packed Boolean collection that C++'s "vector<bool>" has. Does "[Bool]" currently have the option of packed optimization, or would it have to be added via a proposal? Or does it have to be a separate type instead?
It has to be a separate “bitvector” type.
FWIW, C++’s vector<bool> optimization is widely considered to be a bad idea, and many people have talked about trying to remove it from the C++ standard entirely.
Right.
-Chris
On Jul 3, 2016, at 3:49 PM, Xiaodi Wu <xiaodi.wu@gmail.com> wrote:
As an additive thing, probably not much chance of seeing it in Swift 3, then?
This is actually a Google Summer of Code project I'm working on to be added to the swift-collections package! My API Review will be posted momentarily!