From P.H.Welch@ukc.ac.uk Sun Oct 31 15:49:04 2004 From: P.H.Welch To: java-threads@ukc.ac.uk, occam-com@ukc.ac.uk Date: Fri, 22 Sep 2000 17:56:28 +0100 Subject: Re: "No aliasing = no garbage collection" Message-ID: < ... forwarding ... > From: Ruth Ivimey-Cook Subject: Re: "No aliasing = no garbage collection" In-Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed 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