Mailinglist Archive: opensuse (686 mails)

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Re: [opensuse] 64 bit vs 32 bit RAM consumption
Werner Flamme said the following on 07/23/2013 02:45 PM:


If you have to add 2 and 3 it will take the same time on both archs. 64
bit is not faster, it is larger. Compare a road truck of 6 wheels to
another of 12 wheels and double length.

Huh? That doesn't make sense to me?
Can you explain it it detail - and drop the analogy.

Give op-code example. Doesn't have to be from a real machine, just hypothetical.



If you define 64bit integer variables and you store the values 2 and 3

... those are small integers ...


inside those, the 64bit math will be a faster, since it requires only
one register operation (per variable). On 32bit architecture, it may
take two - unless you have a compiler that is smart enough to check for
zeroes before adding ;-)

Again, that doesn't make any sense. What zeros?

Yes, 64-bit math will be faster, that is math involving integers greater than 2^32. How often do we do that? Apart, that is, from calculating addresses when we have an address space greater than can be addresses with 32-bits. But surely you're not doing that 'as arithmetic' but letting the compiler figure out the code for a pointer into an array.

And I hope that you're not dealing with arrays of more than 2^32 elements ...


What's that? Large text strings? You mean 'books'?


--
The Soft overcomes the Hard
The Slow overcomes the Fast
Let your workings remain a mystery
Just show people the Results


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