3 lecture_oct14_constructiveLearning

3 lecture_oct14_constructiveLearning - Problems with BP...

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Copyright Thomas R. Shultz 1 cc 1 Constructive learning cc 2 Problems with BP Too slow Too artistic Levels? Units per level? Restrictions on connections? cc 3 Why is BP so slow? Step-size problem Moving target problem cc 4 Step-size problem weight error cc 5 Quickprop (Fahlman) curvature slope w = Δ 1 2 1 2 w w s s curvature cc 6 Moving target problem Each hidden tries to become a feature detector to contribute to solution But all units are changing
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Copyright Thomas R. Shultz 2 cc 7 Herd effect Units must decide which subtask to solve If A generates larger or more coherent error signal, then units Once A is solved, they move toward B, so A reappears cc 8 Network output phases Output units Input units Hidden units cc 9 First network input phase Input units Output units Candidates cc 10 End of first network input phase Input units Output units Best candidate cc 11 Second network output phase Input units Output units New hidden unit cc 12 Two-spirals -7 -3 1 5 -7 -3 1 5 x y
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Copyright Thomas R. Shultz
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3 lecture_oct14_constructiveLearning - Problems with BP...

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