What gets the best MPG: 1 Sports Coup or 4 Compacts?

[SageBrushfire]

This is going to sound kind of strange but I'm writing this paper comparing computer processors to cars and I'm trying to figure out what would be more efficient.

I need to transport 32 people from one location to another. There's no traffic.

I have two options:

1 V8 Sports coup that seats 4 and gets 12MPG & we'll be driving at 100 mph the whole time!

4 V4 Compact Sedans that seat 4 each & get 24MPG but we'll only be driving at 25mph the whole time.

So what would allow me to move all those people the fastest and/or the cheapest?

I know this is kind of a math question but I'm trying to determine if using multiple high MPG sedans is more effective than one low MPG coup. With the sedans I only have to take 2 trips but I'm using 4 cars. With the coup I take 8 trips and only use 1 car.


Thanks in advance.

[Wyldesoul]

Depends upon your definition of efficiency. (actually, it doesn't, after calculations were done)

The compacts will definately get it done with less fuel used, however, time wise...

Given 100 mile distance, the compacts will take...

Let's see. 3 total "legs" at 4 hours each (there, back, there), 12 hours.

Sports car.... 8 trips, 15 legs (there, back, there, back, ect...), 1 hour each leg.... 15 hours.


The 4 compacts win in that aspect as well. Though they are only 1/4 of the speed, the multiple cars allows them to not waste all that time on return trips.

[Project84]

Sage, you should pay closer attention to logistics.

This seems like homework, and well, you won't learn anything if you don't figure it out for yourself! Biff was more on-key w/ the "legs" comments. Cars can't drive themselves!

[SageBrushfire]

Originally Posted by Project84

Sage, you should pay closer attention to logistics.

This seems like homework, and well, you won't learn anything if you don't figure it out for yourself! Biff was more on-key w/ the "legs" comments. Cars can't drive themselves!

^Heh I know it does sound like homework but I've already got my degree, I'm past all that.


This hypothetical would probably have to assume that you have 3 helpers or family members that can drive with you should you choose option B. (And Actually I guess I should assume each car holds 4 passengers, 1 driver for the sake of simplicity).

I'll post the paper so you can see what I was talking about but I gotta finish it first.

[Wyldesoul]

I imagine the point of the paper is just to demonstrate how a quad-core with an "equivalent speed" (or something along that lines) is superior to an equally powerful single core, correct?

[theholycow]

If we're talking about multi-core processors there are some different effects at work. The example that comes to mind is that a heavy, greedy, or runaway process will hog a whole core - and that's regardless of whether you have multiple cores or not. I often have one core completely saturated but I can still use my system without any slowness because the other core is available for normal processing.

For a single heavy data-crunching task I'd rather have two heavy-duty cores than four less capable cores, but for lots of little stuff (moving 32 people) or daily average usage I'd prefer more cores at the cost of lower speed per core.

[SageBrushfire]

Originally Posted by Biffmeistro

I imagine the point of the paper is just to demonstrate how a quad-core with an "equivalent speed" (or something along that lines) is superior to an equally powerful single core, correct?

Yeah pretty much, but also this:

Originally Posted by theholycow

If we're talking about multi-core processors there are some different effects at work. The example that comes to mind is that a heavy, greedy, or runaway process will hog a whole core - and that's regardless of whether you have multiple cores or not. I often have one core completely saturated but I can still use my system without any slowness because the other core is available for normal processing.

For a single heavy data-crunching task I'd rather have two heavy-duty cores than four less capable cores, but for lots of little stuff (moving 32 people) or daily average usage I'd prefer more cores at the cost of lower speed per core.

See I'm thinking the V8 car will be way better if you just need to get 1-4 people from point A to point B fast (If you have one process that needs to get done fast) while the sedans will be better when you have multiple places to go.

Thanks for the information. I have a first draft if you're interested. I still need to revise it heavily, I don't think I really covered everything I wanted to.

Sorry for the strange formatting but we don't seem to have Spoiler tags on this forum.

Computer Processors and Automobiles


	I was reading about processors one day and an idea popped into my
head. Processors are a lot like cars (and like a great deal of things
but cars are an especially accessible comparison). What sparked this
was my own curiosity about processor speed vs. cores. I was wondering
if a 12.0 GHz single-core processor would be as effective as a 3.0Ghz
quad core processor. 	

At a glance it seems like they'd be almost exactly the same. Four
cores at 3.0 GHz would appear to be as effective as one core going at
12.0 GHz; it's 4 times slower but there are 4 times as many cores.
Then I imagined the processors as cars. The processes were the
people; the starting points and destinations represented individual
programs requesting and completing processes. 	

With this scenario our 12.0 GHz processor becomes a speedy sports
coup with a V12 engine. Wherever we go we'll be driving at up to 120
miles per hour! Our 3.0Ghz quad core becomes 4 separate compact
sedans with minuscule V3 engines. Wherever you need to go you'll have
4 cars at your disposal but the maximum speed is only 30 miles per
hour. 	

Now it becomes clear that each scenario has its own benefits and
detriments. For instance, if you want to take one small trip to a far
off location, you'll want that V12 sports coup. It will get you from
point A to point B much faster than taking one of the sedans. However
if you need to take a large amount of people to different locations,
you're going to want to take the compact sedans. They go painfully
slow but they can be at 4 different locations at once. 	

This is not unlike hyper-threading and multiprocessing in computers.
A single-core processor with an amazing clock rate will accomplish
one process at lightning speed but if you have multiple processes
going on at once, it has to take many different trips and spread its
speed around. A multi-core processor, in contrast, can do all of
these tasks at the same time without breaking a sweat, even if it's
technically slower. 	

And with this we haven't even spoken of efficiency. Our V12 coup is a
total gas guzzler, your best case scenario is that you'll get around
12 miles per gallon. Our 4 sedans, however, get about 24 miles per
gallon, and since they can take a lot more people per trip they have
less overall trips to make. If you do the math you'll find that, in
general, the coup will cost twice as much in gas as the sedans. 	

This we can compare to the wattage and voltage needs of computer
processors where electricity is directly comparable to gasoline. A
12.0 GHz processor would require substantially more electricity to
run than a 3.0 GHz quad-core processor, perhaps much more than just
double the power as in our car example. This makes quad-core
processors far less expensive to maintain. 	

As you can see, there's really no reason to create a single-core
processor that has a ridiculously high speed because you can get
effectively the same performance with much better multitasking
ability and efficiency by having more processing cores. That's
especially relevant today because more than ever we rely on computers
to multitask and handle many different processes at once. Being able
to do one process at lightning speed is a benefit that would only
rarely come into play. 	

This has lead to the progression of processors that we see today.
Clock speeds have been floating around 3.4 GHz for the past 7 years
but cores and threads have significantly increased. Intel's
top-of-the-line Core i7 has 6 cores and hyper-threading, giving you
12 different virtual processing units. Of course CPU's can be and are
often overclocked. It stands to reason that the core/thread boom will
slow down and CPU developers will either turn their focus towards
dramatically increased caches or back to increasing speed. My bet is
on better cache, I wouldn't be surprised if we don't start seeing
processors with 24/48/96MB caches in the future.

[theholycow]

How about the V8 van that seats 8 vs. economy or 2-seat sports cars?

Some thoughts on what you wrote:
- Change "coup" to "coupe". They are two very different things.
- The compacts have inline-3 engines, not V3. A V3 would never be made because it would rattle your teeth off.
- The V12 guzzler won't get anywhere near 12MPG at 120MPH.
- FWIW, I think it was about 10 years ago that clock speeds maxed out at 3Ghz before multi-core processors came out, and the multi-core processors had their clock speed significantly reduced.
- You forgot to take into consideration traffic and speed limits. Just as there are traffic and speed limits on roads, there are on a system bus. It has always been a problem that the rest of the motherboard can't keep up with a single heavy-duty processor, and I think that's part of the reason multi-core processors came about...less cache required, less predicting the future required to fill that cache, a more steady stream of data rather than having to burst enough data to support all that power in chunks.