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Re: [matrix][cssom-view] DOMMatrix operating on single or double precision floating point numbers

From: Robert O'Callahan <robert@ocallahan.org>
Date: Mon, 23 Sep 2013 08:56:50 +1200
Message-ID: <CAOp6jLbyPJmhyyYaEE7MnUN0gRM4CieT8F5CajZn01Qv8KRWdw@mail.gmail.com>
To: Dirk Schulze <dschulze@adobe.com>
Cc: www-style list <www-style@w3.org>
On Sun, Sep 22, 2013 at 1:42 PM, Dirk Schulze <dschulze@adobe.com> wrote:

> Some people objected in using double precision, since double precision
> operations can take more computation cycles, especially on mobile devices.
> The counter proposal is to use single precision floating points and
> truncate on passing double precision values. Truncation to single precision
> and expanding to double precision (for instance to return a DOMPoint) takes
> more time as well. So even that has disadvantages. Note that arithmetic
> operations in JS are done with double precision, internal operations could
> still benefit of single precision operations.
>
> On the other side, many implementations with at least one exception
> (Gecko) operate on double precision already. The web exposed, prefixed
> interfaces WebKitCSSMatrix [2] and MSCSSMatrix [3] for instance are
> operating on double precision values. This already causes accumulating
> errors that can be seen between Gecko's and WebKit's implementation of CSS
> Transforms when applying multiple transformations.
>
> DOMQuad and DOMPoint will be involved in arithmetic operations as well and
> it would be great to find a consensus on the precision question which may
> solve problems on CSS Transforms as well.
>

I'm OK with going with doubles everywhere.

Rob
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Received on Sunday, 22 September 2013 20:57:21 UTC

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