tomleslie

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9 years, 245 days

MaplePrimes Activity


These are questions asked by tomleslie

For the last 24hrs or so I have found it almost impossible to upload worksheet files in response to questions.

My usual approach is

Big green up-arrow:
(uploader pop-up appears)

Browse files

(this still works)

Upload file

This is the problem step - I generally just get "waiting for Mapleprimes" in my browser's annunciator box: and I wait, and wait, (as in >5 minutes) and still this step does not complete. Just to be annoying, every once in a while the file will upload as normal, such but success is now the exception

I'm seeing the same issue in Firefox 45.0.2 and Chrome 50.0.2661.75mon Win 7, 64-bit.

Anyone else seeing the same issue?

 

 

The font size in the output pane of the standard interface, interactive debugger is really, really small and I can't figure out how to increase it. (Other than drop my screen resolution from its native 2560x1440, which makes it bigger but "fuzzier" - not a huge improvement for tired eyes!!)

Consider the equation

eqn1:=5^(2*abs(y-1)+2) = (1/15625)*625^abs(y-1);

and note that

eval( eqn1, y=-3);
eval( eqn1, y=5);

both return valid solutions. So why does

testeq(eqn1);

throw a numeric exception.

Given the manual description of testeq(), I would expect it to return either true or FAIL - but not a numeric exceprion!!!!

Any ideas?

 

Consider the following code, which just generates two "identical" matrices, differing only in their requested storage type, and then does some simple manipulations.

restart;
#
# Define matrix using sparse storage
#
   testM:= Matrix( 40,40,
                           (i,j)->`if`(j>=i,1,0),fill=0,
                           storage=sparse
                        ):
#
# Define identical(?) matrix with rectangular storage
#
   nm:= Matrix( 40,40,
                        testM,
                        storage=rectangular
                     ):
#
# Define procedure to return some matrix properties
#
   matData:= proc( myMat::Matrix)
                            return op(3, myMat)[2], # check storage type
                                      myMat[5, 1..-1], # get 5-th row
                                      add(myMat[5, 1..-1]); # add elements in 5-th row
                    end proc:
#
# Get properies of the two matrices - should be identical
# but check result of adding elements in the 5-th row
#
    matData(testM);
    matData(nm);

The matData procedure ought to produce the same results for the two matrices, with the exception of the storrage type. But the 'add()' command does not. The 'myMat[5, 1..-1]' command produces the same vector, the 5-th row - but stick an add() wrapper around it and all hell breaks loose.

Is this a bug or am I missing something?

Suggestions such as avoiding sparse data storage are not really acceptable: the above is a much simplified version of my original problem where I was using graph theory to play with a "cost function" and (with G a graph) the command,

WeightMatrix(MinimalSpanningTree(G))

returned a sparse-storage matrix - and I didn't notice. There appears to be no option on the WeightMatrix() command to control the storage tyoe of the returned matrix. Result was that all subsequent code based on slicing/dicing/and particularly 'add()ing' sub-blocks of this weight matrix fell apart

Don't get me wrong: I can sort of accept that the weight matrix of minimal spanning tree would (hopefully) be mainly zeros so sparse-storage might be a good default option but I don't see why the results of a command such as

add(myMat[5, 1..-1])

should vary depending on the internal storage used for the matrix, particularly when I have no control over the storage type being adopted

 

Tried posting responses to a question this evening. Click the question title, hit the "reply" button and enter a phrase like "Clarification" in the Title filed of the reply form, the reply form just disappears. Tried this in Firefox and Chrome - same behaviour. Means I can no longer contribute - has somebody broken something??? Or I have a problem with *all* my browsers

PS not even sure that this post will appear correctly

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