LFD Book Forum Homework 6 #10
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#11
05-14-2012, 01:23 PM
 cassio Member Join Date: Apr 2012 Location: Florianopolis - Brazil Posts: 16
Re: Homework 6 #10

Quote:
 Originally Posted by Yellin There may be some confusion here between "nodes", which are the little circles in the neural net diagrams, and "units", which are the x's that enter and leave the circles. So mibeeson's example may mean there are 2 input units, of which one is constant, with two nodes, each receiving the two input units and producing one unit each. Adding one constant unit to the two units from those two nodes makes for 3 hidden units; the three go to one output node, which produces the output unit. Each node needs weights for each of its incoming units, so there are 4 weights from the first layer of nodes plus 3 from the three units entering the output node. Is this reasonable, or am I the one who is confused?
Yellin, in my understanding you are right in the example you gave. And I would like to add the other interpretation of the problem proposed by mjbeeson where rohanag opened my eyes: if I have 2 input units (one of them is the constant) and one node that receive both connections from the input units. Now to next layer, I have the unit value from the node and one constant unit (what result in two units in this hidden layer), both connecting with the output node. Thus, I have two weights in first part and more two in the last. Am I right?

Last edited by cassio; 05-14-2012 at 01:37 PM. Reason: grammar
#12
05-14-2012, 01:48 PM
 mjbeeson Member Join Date: Apr 2012 Posts: 25
Re: Homework 6 #10

I don't think that's the way we are to read the homework. Notice problem 8, where it says,
"10 input units (including the constant value)...and 36 hidden units (include the constant inputs of each hidden layer).
The "including" part important in the counting.
#13
08-16-2012, 06:00 AM
 dvs79 Member Join Date: Jul 2012 Location: Moscow, Russia Posts: 24
Re: Homework 6 #10

Has anybody got the correct answer? My answer was wrong and I can't see where is a mistake in my reasoning.
The maximum number of weights should be for the network looking like 10-18-18-1 (including constant nodes in the first three layers), right? But number of weights for it is not one in the answer key.
#14
08-17-2012, 09:01 AM
 Keith Member Join Date: Jul 2012 Posts: 16
Re: Homework 6 #10

I got this one right. I used Excel (of all things) to explore all arrangements with one and two hidden layers, and also looked at portions of arrangements with more hidden layers. The spreadsheet does the arithmetic with simple copied formulas and gives the correct answer without too much work.
#15
08-17-2012, 01:39 PM
 dvs79 Member Join Date: Jul 2012 Location: Moscow, Russia Posts: 24
Re: Homework 6 #10

Oh, I see. My stupid blunder.

Thnx!
#16
08-21-2012, 12:33 PM
 DavidNJ Member Join Date: Jul 2012 Posts: 28
Re: Homework 6 #10

Now I feel like an idiot!

You could also have used goal seek in Excel.
#17
08-21-2012, 02:08 PM
 tzs29970 Invited Guest Join Date: Apr 2012 Posts: 52
Re: Homework 6 #10

In case anyone is curious, there are 9227465 possible networks that satisfy the constraints of this problem.
#18
02-13-2013, 03:02 PM
 ilya239 Senior Member Join Date: Jul 2012 Posts: 58
Re: Homework 6 #10

Quote:
 Originally Posted by mjbeeson Counting weights. Just to clarify if I am counting right: suppose we have 2 input nodes and one hidden layer with 2 nodes and one output node. So then we have 4 weights, right? According to the problem statement the constant input nodes are counted in the "2". Similarly if every input or hidden layer has an even number of nodes then we must get an even number for the total number of weights. Do you agree? Or do I have an off-by-one error in this count somehow?
"2 input nodes", does that include the constant node or not? I.e. does layer 0 look like or like ? What's the right standard terminology to use here?
#19
02-13-2013, 06:02 PM
 yaser Caltech Join Date: Aug 2009 Location: Pasadena, California, USA Posts: 1,478
Re: Homework 6 #10

Quote:
 Originally Posted by ilya239 What's the right standard terminology to use here?
In the statement of this problem (preamble before Problem 9), the constant variables are counted as units.
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#20
02-17-2013, 09:15 AM
 spramod Junior Member Join Date: Jan 2013 Posts: 8
Re: Homework 6 #10

Professor, after the deadline, could you please post an explanation to this and Question 9, if there's a general case analytical solution, or if there's any other straightforward method?

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