Re: "No aliasing = no garbage collection"

["P.H.Welch" <P.H.Welch@xxxxxxxxx>]

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From: Ruth Ivimey-Cook <Ruth.Ivimey-Cook@xxxxxxxxxx>
Subject: Re: "No aliasing = no garbage collection"
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At 13:30 22/09/00 +0100, you wrote:
>} In my opinion, garbage collection is an efficiency mechanism.
>} Conclusion (assuming I remembered correctly that the proof can be done):
>}   if you are not bothered with performance, use a garbage collector,
>}   and save on memory budget, use virtual memory as well.
>}
>}   if you are bothered with performance, buy twice as much memory, and
>}   do not use a garbage collector, nor virtual memory.  Simply, use
>}   enough memory.
>Yes, I agree...
>
>The temptation to attach every bell and whistle is a strong one.
>But that problem becomes an opportunity when you remember that
>implies that the niche of clean, understandable simplicity is
>almost unoccupied.
>Larry

I am slightly worried by this view. The experience of many ARM customers, 
working in the embedded space, is that memory is definitely not cheap. The 
reasons are:

1. What memory you have must be on-chip with the processor, which mostly 
limits it to small quantities of SRAM and slightly larger quantities of ROM 
or EPROM.

2. The cost of many consumer items is a multiple of the manufacturing cost. 
That is, if it costs $5 to build, it costs $50 at the retailer (and that is 
perhaps understating the multiple). Consequently, adding a $10 DRAM to a 
design is not an option -- it would add $100 to the selling price.

3. Items like mobile phones typically have huge memory requirements -- 
3-5MB ROMS is not unusual, and RAM is also needed in large quantity. And 
yet if you look inside these devices you find only a couple of chips. 
Doubling the physical space required for memory is not possible -- it 
doesn't fit.

I believe there should be a garbage collection scheme added to occam. It is 
a great language for many things, but it is let down in areas which people 
care about intensely.

Regards,

Ruth