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What Would Have Happened If Philae Were Nuclear Powered?

matfud Re:I'm quite surprised it wasn't (480 comments)

Philae does not have fold out solar panels. It is covered with panels but nothing to fold out. So not mass budget there.
The whole thing has a mass of about 100kg. There is not much to spare in it.

2 days ago
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Halting Problem Proves That Lethal Robots Cannot Correctly Decide To Kill Humans

matfud Re:By the same logic (314 comments)

"The stick does not have wires of hydraulics "
"The stick does not have cables or hydraulics connected to the flight surfaces. You had better hope them computers keep working"

sorry just random typing mistakes.

2 days ago
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'Star Wars: Episode VII' Gets a Name

matfud Re:My predictions (267 comments)

Sorry that is knowledge after the fact. I did not know it. I looked it up a few days after I said I thought C3PO did not have a skin. At some point it started to bother me so I looked it up. I'm not sure how much of that is retrofitted just to allow the droids to be in the first 3 movies.

Nevermind!

2 days ago
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'Star Wars: Episode VII' Gets a Name

matfud Re:My predictions (267 comments)

I did actually look around to find out why Darth Vader did not know C3PO and vs versa.

When they made the prequels they did consider it. Hence C3PO not having a skin for the first two films (why darth vader does not know him). And why C3PO is ordered to forget everything at the end of ep3 (so he does not know darth vader)

Woooo that is far more than I wanted to know about starwars. I thought it was cool when I saw the first three back to back in a cinema in the 1993. I had seen them before but never in a cinema :)

2 days ago
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Halting Problem Proves That Lethal Robots Cannot Correctly Decide To Kill Humans

matfud Re:By the same logic (314 comments)

Military aircraft went beyond that in the 1980's (experimented with in the 70's) They are unstable. Impossible to fly without computers.

Most modern airliners are also not possible to fly without the computers working. Not because they are unstable. But because the are fly by wire. If the computers fail. and fall back. and that fails. and they fall back again and that fails you can not move the wibbly bits on the aircraft. The stick does not have wires of hydraulics connected to the flight surfaces. You had better hope them computers keep working.

2 days ago
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Halting Problem Proves That Lethal Robots Cannot Correctly Decide To Kill Humans

matfud Re:By the same logic (314 comments)

People are still in control because there are many reasons why a target is not a target.

Phalanx and even older weapons systems can work in fully autonomous modes. (TELAR, PATRIOT and other missile defence systems can also do so).
They are not used in that way as if they are then a match is good or bad based on what they know. What they know is not very much. They are not listening on VHS for example, to some pilot saying "opps, sorry. Where exactly are we?" or a sailor saying "We are a trawler and have nets out. We can't get out of your way please avoid"

There are lots of reasons why things go wrong and hopefully a human in the loop can assess the out of band information and make a good decision.

 

2 days ago
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'Star Wars: Episode VII' Gets a Name

matfud Re:My predictions (267 comments)

Did he make a gold droid?

I ain't a star wars fanatic. I thought c3po did not have any covering (in ep 1)

about two weeks ago
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Space Tourism Isn't Worth Dying For

matfud Re:The Golden Gate Bridge (594 comments)

Most transatlanic air flight is just for fun. Most is for people going on holidays. That still has a demostrable and economic and societal purpose. And a massive enironmental impact.

But I agree with you.

Risk is something each person chooses in this kind of endevour. Why have there always been so many astrounauts in the US space program? They are the best of the best of all that apply and yet they still want so sit on many hundreds tons of BANG.

Test pilots may be nutters. As long as they knew what they were getting into (and I think they would not take a chance if they did not know) (well maybe as they are nutters) all the best for them.

about three weeks ago
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Space Tourism Isn't Worth Dying For

matfud Re:Well (594 comments)

Of the 700 ton (700,000kg) remaining mass the second stage (480 ton) 480,000kg took it from 7,880 f/s to 21,368 f/s velocity at 101 nm altitude
The third stage 128 ton (128,000kg) stuck it into orbit at 24,000f/s and was then used for the translunar orbit burn.

The rest of the mass went to the moon. Landed and returned.

Not exactly efficeint.

Sorry the GP's claim of 10 percent is so wrong I thought I would see exactly how wrong it was. And the answer was very very :)

about three weeks ago
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Space Tourism Isn't Worth Dying For

matfud Re:Well (594 comments)

I agree with Karmashock.

Look at the profile for apollo 11.

http://history.nasa.gov/SP-402....

stage 1 sthutoff is about 36 nm altitude 51 nm down range. While that may seem fast I think it is only at a 35deg angle to verticle at the time.
it weighed 3,000,000kg and the first stage was 2,300,000kg of that (total weight)

about three weeks ago
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British Army Looking For Gamers For Their Smart-Tanks

matfud Re:No respawns (163 comments)

In british callenger 2 tanks he is. It is manually loaded.

But I have no idea if that can cause fingers to get stuck and severed.

about a month ago
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Fuel Efficiency Numbers Overstate MPG More For Cars With Small Engines

matfud Re:metric you insensitive clod! (403 comments)

Even NASA's crawler transporter gets 42 feet/gallon

about a month and a half ago
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Why the Z-80's Data Pins Are Scrambled

matfud Re:gear heads (167 comments)

Damn you you opposed piston engines (which balance pretty well)

about a month and a half ago
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Why the Z-80's Data Pins Are Scrambled

matfud Re:C=128 (167 comments)

Quite possibly :)

about a month and a half ago
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Why the Z-80's Data Pins Are Scrambled

matfud Re:Why is it necessary to reverse engineer this? (167 comments)

When your data and or instructions are not aligned on cache boundries and/or not limited by them (4k seems pretty standard for x86 and x64 3rd level caches but the processor may have different ideas about how that is segmented for L2 and L1) then you can cause cache thrashing by trying to tune for those specific variables. (your can cause the same by not tuning for them)

You say that it is remarkable how uniform current platforms are? I am interested as to why you think that as even on just x86 and x64 there are huge differences.

Anything "exotic" excluded.
chuckugly I like to learn :)
I would like to hear why you think that. I know you can boost some tight loops by many factors if you can get then in the L1, L2, L3 cache I may learn something. For larger scale dataprocessing it can be very tricky to keep the instructions in a cache page with regularly changing data (used in small blocks) also in the cache.

And no it is not easy and never has been. It can be remarkably hard on anything other that a micro-optimisation

 

about 2 months ago
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Why the Z-80's Data Pins Are Scrambled

matfud Re:Why is it necessary to reverse engineer this? (167 comments)

I am not disagreeing with you but some of the things I pointed out above are varibles with respect to harware and most of them DO affect memory locality. If you make an assmption that x parts of data are localy cached you can be truely wrong when run on a compatable chip with a different cache layout or even the same chip but with a different offset that is only partialy aligned with the cache.

Some algorithms in general tend to keep the data used close to gether and they may benifit. Some algorihms uses data in chunks scattered all over the place but the chunks are particularly freindly for the system and they work well (keeping it cahched well).

But as I said it is remarkably hard to do those kinds of optimisation without a particular system to run on.

about 2 months ago
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Why the Z-80's Data Pins Are Scrambled

matfud Re:C=128 (167 comments)

SKIP does seem a bit limited if it is only one entry that it skips.
I think you either overran the time to execte so events had already occured or you finished early and waited for the next frame/whatever.

So how did workbench give provide windows containing HAM8 images or where they only full screen windows with a menu bar? (too long ago and I do not remember). I was using PC's back then but I was most impressed with a flatmates Amiga. Shame it struggled to run Elite :)

about 2 months ago
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Why the Z-80's Data Pins Are Scrambled

matfud Re:gear heads (167 comments)

But do you know WHY a V8 does not fire in ascending order?

about 2 months ago
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Why the Z-80's Data Pins Are Scrambled

matfud Re:5v lines (167 comments)

Many modern chips that have analog components have the analog supply and ground close to the pins used for the analog functions (for pretty obvious reasons)

You many no longer be worried about running a few extra digital datapaths to make the outside data bus be in order but you still need to seperate analog and digital functions and that limits the output pins they can use

about 2 months ago

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