Re: 48-bit fixnums

[Bruno H. <br...@cl...>]

Sam wrote:
> and what does adding 2 bytes to each vector have to do with this?

It's not 2 bytes, it's 8 bytes: First, when a length field increases from 4 to 8
bytes, it's +4 bytes. Due to alignment reasons (on 64-bit platforms,
varobject_alignment is 8), it's either +0 or +8.

> this will add
> (* 2 (+ 11246 4638 2936 292 495 95))
> 39404 bytes - less than 40k to a 2M image - 2%.

No, it will add either 0 or 160k to a 2MB image - 0% or 8%. And 8% more memory
means typically 16% slowdown (rule of thumb).

Now, when you look at the definitions of VAROBJECT_HEADER and VRECORD_HEADER,
you see that on 64-bit platforms there is currently a hole of 4 bytes in the
header. So it's really +0% more memory. !! :-)

Bruno