From: Tulloch, Ed
Date: 04/22/2002
Subj: Questions

What does tiac signify? I don’t seem to have access even to the home domain level (www.tiac.net). I’m tld I must specify a username.

Tiac stands for The Internet Access Company. They were my original ISP in 1996 when I started the site. Since then the company was acquired and then sold. Currently the tiac customers are serviced by us.inter.net. I keep the site and the address because there are a zillion links to my site. Well, maybe not a zillion, but a lot. Generally speaking the .net extension signifies an ISP rather than a web site.

There was no doorway, just uprights. My recollection is that the depth of the boat was greater than the distance between the uprights. I wouldn’t count on the reliability of that memory, though.

Thank you for the kind words. I haven’t gotten much volleyball in whilst living in SD. I expect to visit my old haunts this summer; we shall see if I remember how to play the game.

Return to index of contributors

From: Charles Hitchcock
Date: 04/19/2002
Subj: various

Random comments:

Jackson Hedrick seems unaware of the history of computing; 1887 was decades after Babbage had “the first software project to finish late and over budget.”

I hadn’t thought of that. I am reminded of my never completed project to build a steam powered fortran compiler.

Indeed. The notion that in the middle ages people believed that the world was flat apparently is a myth invented by radical atheists in the nineteenth century.

(The real issue was that BU still has ]parietal hours[ in all the dorms. Apparently losing an open-and-shut First Amendment case wasn’t enough to teach Silber’s hand-picked successor to treat students as people — he told the protesters to piss off until they could bring 3,000 people to a demonstration. May he get what he wishes for.)

Some decades someone observed that American university’s notion of loco parentis was to assume authority over students but avoid responsibility for students, aka “We get to make the rules and hardass you with them, but if you get into trouble fuck off and die – we don’t know you.” I am not a fan of John Silber; at least Ghengis Khan had panache.

I’m sure I wouldn’t know and I will thank you kindly not to wonder.

It’s probably just another urban myth, but several years ago I heard about an official at the old Boston Garden who made the mistake of being rude to some roustabouts because someone from the circus had parked in his space. The story goes that he learned about elephants the hard way; they were backed up to his car before being stood up.

I hope he had a convertible.

Those little French restaurants around the corner are disasters for the weight conscious, no way (weigh?) around it. Now that the weather has improved I have taken to walking to town to get the mail. It is a mile and a half each way which makes for a nice little walk. It all seems to be working – I’ve lost 20 pounds so far. One complaint I have is that the pounds don’t seem to come off where you want them to come off. I lost some of that unsightly bulge in the belly – perhaps an inch or two in waist size – but not as much as I had hoped for. However some weight has come off the legs. I hope I don’t turn into one of those old geezers with pipestem legs and arms and an enormous pot belly.

A common belief is that you haven’t lost any weight from your legs — just converted fat to muscle, which is denser. (This was the state of obesology(?) 30 years ago, so it may be out of date.) You can always try abdominal crunches….

I’m not sure about that theory; I have a lot of fat in my head and I’m very dense. I’ve been doing a few situps now and then – they’re a lot harder than I remember them being.

From: John Puzzo
Date: 04/16/2002
Subj: Weight loss

prune juice and enemas

works every time

don’t bother to thank me

Don’t worry, I shan’t.

From: Wanda C
Date: 04/15/2002
Subj: Collected Humour

Just thought I would drop a note to say that the collected humor section is great and seems to kick start my day to being positive… Keeping adding these stories since it can turn a bad day into something very “positive”

Your wish is my command – provided, of course, that you make the right wish.

From: Sheena Caines
Date: 04/14/2002
Subj: Hi

I am 16 and I want to join the Marines after college. I know in teh interview for the scholarship, they ask you questions about the Marine Corps. I dont really know that much about it, so I figured since you were in it, you could help me out.

I’m puzzled; what scholarship are you talking about? It doesn’t sound as though the Corps is a pressing issue for you if it’s something that you want to do after college. That’s a long time for someone who is 16.

I am talking about the 4-year NROTC scholarship for college.

Aha. There are three things standing in your way. The first is the physical – you will have to be physically fit. There’s not much you can do about that; either you are or you aren’t. The second is your grades and your IQ. Again there isn’t much you can do about that – either you have the right stuff or your don’t. The third is the interview.

My take on this is that you should be honest, i.e., instead of trying to figure out what they want to hear, figure out what you want and why you want it. The one big thing they will want to know is: Why do you want to do this? That is the thing that you should think about, not just for the interview but really for yourself.

From: Thetallones
Date: 04/08/2002
Subj: Hmmm…(about the next show)

Interesting!! But I am looking for the show that sends people back on an island or to some place and who-ever stays the longest gets 1 million dollars!! Can you please help me find a application to get on that show!!

Thanks for all of your help!! Ohh by the way the show sounds really cool to see what men are really like!!

You’ve written an interesting letter but it doesn’t seem to have anything to do with my site. The show you are talking about is Survivor. Check out the CBS website for info on the show.

I found your email and reference to a histogram sort tool that you’ve developed at http://www.nist.gov/dads/HTML/histogramSort.html

Do you make that code available? I’m doing an assignment, and need to do a frequency analysis of a large set of numbers (too large to fit into Excel).

You could have a copy of the code for the sort routine but I doubt that it would be of much use to you. I don’t have a histogram application as such; you would have to write some code to make use of it. It might help if I knew what environment you are in and what resources you have at hand.

From: AngelAce141
Date: 03/30/2002
Subj: question

Hello. I am writing a philosophy paper on CS Lewis, and I found your analysis on him quite interesting- I got a lot out of it. I do have a question for you, though, if you don’t mind my asking. You stated that Lewis focused on small aspects of human sin rather than larger instances happening (such as your example of death camps). I was wondering- why do you think Lewis approached the smaller aspects rather than the larger ones in life?

That is a good question and I’m not sure that I have a good answer. One can approach the question in two ways. One can ask can what was it in Lewis’s personality and situation in life that led him to consider the small aspects. Alternately, one can ask what roles the small and the large played in his conception of Christianity.

One could argue that Lewis led a small life. The central focus of his life was the fairly narrow world of the university. The observation, then, is that he wrote about the sort of thing with which he was familiar. This is a common enough phenomenon; many philosophers approach the problem of pain by considering the toothache. Following this line one might look carefully at the sorts of characters that occur in his fiction. This approach is necessarily speculative but it could make for lively and interesting prose.

One can also argue that Lewis had the right of it from the Christian perspective. There is a difference between being good and doing good. To deal with large scale suffering and misfortune requires social effort on a large scale; this social effort does not necessarily require that those engaged in the effort are nice people. The story of the humanitarian who does much good and yet is mean-spirited in his personal life is an old one. Christianity, however, asks that you be good rather than merely doing good. In this regard the small sins are more important because they are more immediate and personal. The Screwtape Letters are a good illustration of this thought.

One can explain his preference for the small over the large along these lines. However that does not explain the deficiency in his conception of evil. In my essay, A Christmas Carol Revisited, (which should not be taken seriously) I write:

As Orwell points out in his essay on Dickens there are two reactions, two advocacies, that can be made in response to the evils of the world. One is to urge humanity to have better hearts; the other is to urge humanity to change the system by which it orders its affairs. Dickens, Orwell writes, chose the first course.

Lewis, I suggest, follows the same course as Dickens. The defect of this approach is that it does not recognize that an evil system does not require particular evil on the part of those within the system. That is, evil in the large is not simply the sum of the small individual evils. It may have been that Lewis had no place in his thinking for this phenomenon.

From: Rebecca Hart
Date: 04/03/2002
Subj: Guide to Hiring Women

I’m wondering if you can tell me where you got the ‘Guide to Hiring Women’ you have posted on your about.com site. Have you actually seen the 1943 issue of Transportation Magazine, or did you get it via someone else? I’m looking for the actual original article, having trouble finding it. Thanks, Rebecca Hart

I haven’t actually seen the said 1943 issue, and to be honest I have doubts about its existence. The guide circulates on the internet. It may be genuine though; it isn’t that far from the reality of the day.

From: Carolyn Bagley
Date: 03/26/2002
Subj: horses and such

I really enjoyed reading about your history with horses. I used to ride as a kid, my parents say I rode my first rocking horse until it fell apart. The seed was planted early I guess.

At any rate, it has been many years since I have owned a horse but growing up I had two ponies and one horse. One was killed in an accident, sadly, the other two eventually handed down to my younger sister. We had them until they passed on.

I am 42 now and recently splurged on a riding lesson. I rode English growing up and you are right, it is harder and it is easier to look like you know what you are doing more quickly riding Western. Just the hard truth. But, having confidence and feeling comfortable on a horse is the key, bottom line.

Anyhow, I was sore for at least two weeks after that lesson and got no further than a trot. Kept trying to post and realized what a strong kid I had to have been, it was just all so much easier back when I was 10. I would love to ride again and maybe one day I will find a stable run by someone like Helga. That would sure be nice. Loved your story.

I enjoyed your letter. I haven’t ridden for a good while. I suppose I shall again one of these days but I expect that I shall be very sedate. The old bod is not quite as supple as it was in my salad days and my knees are definitely shot from playing twenty years of competition volleyball.

From: Wim Mortier
Date: 03/19/2002
Subj: Optimizing the merging of sorted arrays: what about the intersection of two sorted arrays?

one of the articles on your site is on “Optimizing the merging of sorted arrays”

“Suppose we are given two arrays, x and y, that are sort in ascending value and that we wish to merge them into an array z. (This is the inner loop operation in merge sorts.)”

I’m looking for an algorithm that does just that. My book on algorithms and data structures mentions binary search, binary trees, hash lists, nested loop joins, … big O notation, … My goal is of course to minimize the number of comparisons.

I suppose the size of array A and B influences the choice of the algorithm.

Given A: a sorted array of n numbers and B: a sorted array of m numbers,

If A and B are identical, the number of comparisons is 5, that’s the smallest number of comparisons one can get. (using a nested loop join)

A   B
1   1
2   2
3   3
4   4
5   5

So: log 2 (100) = 7 => to be repeated 3 times => 21 comparisons at most.

If n = 100 and m = 100, and both arrays are identical, the best algorithm will have to compare only 100 times. If I use a binary search in this case, I would need to compare 7 x 100 times. Far slower.

At what point does a binary search become faster than a nested loop join? B needs to be a lot bigger than A to gain speed by using a binary search. But how much bigger?

Could this be true?

If n is x times smaller than m, then a binary search is faster, given x = log 2 (m).

I’m not a scientist or number cruncher, just a guy trying to get software a bit faster.

Your problem is simpler than you think it is. The simple way to do this, given sorted arrays x and y of lengths n and m, is to use two pointers, one in x and one in y. The code looks something like this in C:

for (i=0, j=0, k=0; i<n && j<m;) {
     if (x[i] < y[j]) i++;           /* x[i] is small, advance i */
     else if (x[i] > y[j]) j++;      /* y[j] is small, advance j */
     else {                          /* x[i]==y[j], output x[i], adv i and j */
           z[k] = x[i];
           i++; j++; k++;
     }
}

This code is O(n+m). You don’t have to sort the arrays though. You can set up a hash table. First enter one array into the table and then walk through the other array, checking each value in the second array to see if it is present in the table, outputting those values which are present. Again the cost is O(n+m).

Is this clear or do you need more detail?

thanks for the response, the source and the Big O notation of the discussed algorithms.

Let’s elaborate: I have the luxury (?) of receiving nothing else but sorted arrays. So I want to exploit this fact. I’m also calculating the intersection of _multiple_ sorted arrays. So I’ll have to intersect them one by one, or use another algorithm. (?)

Talking about costs:
array A: 35 elements
array B: 35 elements
nested loop/hash: 35+35        = 70    <-- faster
binary search: 35 x log 2 (35) = 180
array A: 35 elements
array B: 500000 elements
nested loop/has: 500000+35         = 500035
binary search: 35 x log 2 (500000) = 663    <-- faster

If the array sizes are very different, it seems wise to prefer a binary search over a nested loop or hash.

Are there flaws in my logic? If my assumption is true, how big does the size difference need to be to prefer binary search over a hash/nested loop?

If you run a comparison loop the number of comparisons is ~ n+m whereas in a binary search the cost is ~ m*log2(n). You can solve this to get

m0 = n/log2(n/2)

as the break even point, i.e., for m.gt.m0 use the comparison loop and for m.lt.m0 use the binary search. However it isn’t that simple.

Given the same number of comparisons the comparison loop is faster than the binary search because the logic is simpler. Ergo m0 is smaller than indicated by our formula.

On the other hand you can, at the cost of more complicated logic, use a more efficient search algorithm by taking into account the results of previous binary searches. Thus, suppose array A has n elements and B has m elements and you do a binary search of A for B[0] (assuming 0 indexing) to find A[k] matching B[0] for some k. When we search for B[1] we only need to examine the range A[k-1] to A[n-1]. Each search reduces the range required for the next. The obvious thing to do is to use the same trick that we use for the binary search. That is, given A and B, we search A with B[m/2]. Having found A[k] matching B[m/2] we search A[0]…A[k-1] with the lower half of B and A[k+1]..A[n-1] with the upper half of B. I will have to check to see if Knuth gives the analysis for this trick.

In any case, given that you want the intersection of several lists you will probably want to use both the comparison loop and the binary search with a cost test.

From: Clark Whelton
Date: 03/05/2002
Subj: Request

Can you tell me where I should look, or whom I should ask, to find the name and author of a science fiction story I read in the 1950s, probably 1953-55 in Astounding, Galaxy, or Amazing Stories.

The story is about criminals in the future who are exiled to a prison planet. But instead of landing in a prison colony, they find themselves in the midst of a dangerous, alien jungle. They have to work together to fight their way to safety. Later they learn that the colony got tired of being overwhelmed by the periodic arrivals of criminals, so the newcomers were dropped in the jungle. Only those who learned the hard way to cooperate and help each other survived.

I’ve always wanted to read this story again. If you have any suggestions, I would be most grateful.

With thanks in advance, Clark Whelton [email protected]

I don’t recognize it off of the top of my head but I have posted in inquiry in the rec.arts.sf.written. One of the sharks there will probably recognize it.

From: RedLeaf19
Date: 03/13/2002
Subj: North/South Station puzzle

That North/South Station puzzle was probably the stupidest riddle I have ever seen. The answer doesn’t make any sense and its not creative

Come on. Don’t be shy. Tell us what you really think about it.