Carl Love

Carl Love

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12 years, 333 days
Himself
Wayland, Massachusetts, United States
My name was formerly Carl Devore.

MaplePrimes Activity


These are replies submitted by Carl Love

Results are nearly unsearchable on MaplePrimes! It's a pity that all that information is going to waste. If the search result is one of my Answers, then you'll need to work your way through a list of nearly 3000 Answers to find what you want. If the true answer appears not in the Answer itself but in a Reply to an Answer, then it's even worse: You won't find it unless you stumble upon it.

An Answer is a terrible thing to waste! I beg the MaplePrimes administrators to simply let Google index MaplePrimes. I've asked for this several times before, with no Reply, not a single word. As far as I know (and I'm definitely not sure about this), this would require almost no effort---you just ask Google to do it.

@John Fredsted Unfortunately my protocol doesn't work in this situation. You either need to wait for the out to display or kill the Java process.

This problem was already solved at the OS level on the first few computers that I ever worked on, 38 years ago (DEC-10 & PDP 11/70). One pressed Ctrl-O to stop seeing the output and Ctrl-O to start seeing it again. Whatever happened to that protocol?

@brian bovril Here's a corrected worksheet. The problem was not randomness but that one needs to call DrawGraph(..., style= spring) first in order to set the vertex positions for the GetVertexPositions command. Then one needs to call DrawGraph again to redo the graph using those positions and the more-elegant vertex labels. This is all to work around a bug.
 

restart:

dist:= Matrix(
   (7$2), shape= symmetric, scan= band[0,6],
   [[0$7],
    [7, 11, 7, 15, 14, 8],
        [4, 12, 16, 5, 6],
             [5, 5, 3, 9],
             [12, 14, 11],
                  [7, 11],
                     [14]
   ]
);

dist := Matrix(7, 7, {(1, 1) = 0, (1, 2) = 7, (1, 3) = 4, (1, 4) = 5, (1, 5) = 12, (1, 6) = 7, (1, 7) = 14, (2, 2) = 0, (2, 3) = 11, (2, 4) = 12, (2, 5) = 5, (2, 6) = 14, (2, 7) = 11, (3, 3) = 0, (3, 4) = 7, (3, 5) = 16, (3, 6) = 3, (3, 7) = 11, (4, 4) = 0, (4, 5) = 15, (4, 6) = 5, (4, 7) = 9, (5, 5) = 0, (5, 6) = 14, (5, 7) = 6, (6, 6) = 0, (6, 7) = 8, (7, 7) = 0}, storage = triangular[upper], shape = [symmetric])

demand:= <100, 200, 120, 45, 250, 80, 75>:

hubs:=[seq(parse(i), i = "A" .. "G")]:

seq(assign(Index(hubs[k])= k), k= 1..nops(hubs));

seq(assign(Vlabels(v)= sprintf("%a %d", v, round(demand[Index(v)]))), v= hubs);

edges:= {{A,C},{A,D},{C,D},{C,F},{D,F},{D,G},{G,E},{E,B},{B,A}}:

subsindets(edges, set(name), e-> [e, dist[Index~(e)[]]]);

{[{A, B}, 7], [{A, C}, 4], [{A, D}, 5], [{B, E}, 5], [{C, D}, 7], [{C, F}, 3], [{D, F}, 5], [{D, G}, 9], [{E, G}, 6]}

edgesL:= subsindets(%, name, Vlabels);

{[{"A 100", "B 200"}, 7], [{"A 100", "C 120"}, 4], [{"A 100", "D 45"}, 5], [{"B 200", "E 250"}, 5], [{"C 120", "D 45"}, 7], [{"C 120", "F 80"}, 3], [{"D 45", "F 80"}, 5], [{"D 45", "G 75"}, 9], [{"E 250", "G 75"}, 6]}

macro(GT= GraphTheory):

G:= GT:-Graph(edgesL);

GRAPHLN(undirected, weighted, ["A 100", "B 200", "C 120", "D 45", "E 250", "F 80", "G 75"], Array(%id = 18446744579093236182), `GRAPHLN/table/1`, Matrix(%id = 18446744579097074606))

These shenanigans with GetVertexPositions and SetVertexPositions are here to compensate for a bug in DrawGraph(..., style= spring). As you can see, the vertex labels are not printed as elegantly as they should be.

GT:-DrawGraph(G, style= spring);

GT:-SetVertexPositions(G, GT:-GetVertexPositions(G, style= spring));

GraphTheory:-DrawGraph(G, font= [HELVETICA,BOLD,10]);

``


 

Download DrawnGraph.mw

@brian bovril I'm sorry, Brian: There is some randomness in the style= spring algorithm that I failed to account for. I'm working on a solution. I don't think that this has anything to do with you using a different version of Maple.

@MDD The package was introduced in Maple 2015.

@MDD Sorry, but the package PolyhedralSets doesn't exist in Maple 15.

What makes you think that there is a solution in the cube (-1000..1000)^3? Indeed, your use of the imaginary I in all three equations leads me to doubt that there are any real solutions. fsolve immediately finds a solution in the complex cube (-1000-1000*I..1000+1000*I)^3.

@tomleslie If you have pressed the button, and the code is still executing (as opposed to simply scrolling spooled output), then the code will stop, eventually, when it returns to Maple-level code. Repressing the button has no effect.

@vv I caught the error and posted the correction while you were writing. But thanks anyway. And I added an expansion of that cryptic code at your suggestion.

@Axel Vogt Hmm. You save first, then kill; I kill first, then save. If you run into another situation where you can't save first, give my method a try. Anyway, I think that's it's faster in all cases, but especially if the mserver is consuming most of your memory.

@Markiyan Hirnyk I edited the Answer, including more explanation. It's very frustrating to me that people would risk losing their unsaved work by killing the Java process. That's totally unnecessary.

@alisha shaikh NB is a standard abbreviation for "note well". The letters come from the Latin phrase meaning the same thing.

If there's any place where f is negative, complex numbers will enter the solution due the fractional exponent of f. It might be beneficial to include an initial approximate solution with f nonnegative.

@Christopher2222 Can you give me an example of what you mean by an attribute? Do you mean a type, like integer, string, etc.?

When you say "call the full list of the Record", do you mean that you want to see the contents of the fields without the field names?

@Vee The % refers to the output of the previous command (even if that output was suppressed). There's also %% and %%%: the former refers to the output of the command previous to the previous command, and the latter refers to the command before that. That's as fas back as you can go.

@Scot Gould Moderators can and do change Posts to Questions and vice versa.

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