>>> import numpy as np 
>>> Pooling_dout =np.arange(432000).reshape(12, 12, 30, 100)
>>> pooling_backward_dout = Pooling_dout.transpose(0, 2, 3, 1)
>>> pooling_backward_dout
array([[[[ 0, 3000, 6000, ..., 27000, 30000, 33000],
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 [ 2, 3002, 6002, ..., 27002, 30002, 33002],
 ...,
 [ 97, 3097, 6097, ..., 27097, 30097, 33097],
 [ 98, 3098, 6098, ..., 27098, 30098, 33098],
 [ 99, 3099, 6099, ..., 27099, 30099, 33099]],
 [[ 100, 3100, 6100, ..., 27100, 30100, 33100],
 [ 101, 3101, 6101, ..., 27101, 30101, 33101],
 [ 102, 3102, 6102, ..., 27102, 30102, 33102],
 ...,
 [ 197, 3197, 6197, ..., 27197, 30197, 33197],
 [ 198, 3198, 6198, ..., 27198, 30198, 33198],
 [ 199, 3199, 6199, ..., 27199, 30199, 33199]],
 [[ 200, 3200, 6200, ..., 27200, 30200, 33200],
 [ 201, 3201, 6201, ..., 27201, 30201, 33201],
 [ 202, 3202, 6202, ..., 27202, 30202, 33202],
 ...,
 [ 297, 3297, 6297, ..., 27297, 30297, 33297],
 [ 298, 3298, 6298, ..., 27298, 30298, 33298],
 [ 299, 3299, 6299, ..., 27299, 30299, 33299]],
 ...,
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 ...,
 [ 2797, 5797, 8797, ..., 29797, 32797, 35797],
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 ...,
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 ...,
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 ...,
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 [[ 36200, 39200, 42200, ..., 63200, 66200, 69200],
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 ...,
 [ 36297, 39297, 42297, ..., 63297, 66297, 69297],
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 [ 36299, 39299, 42299, ..., 63299, 66299, 69299]],
 ...,
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 ...,
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 [ 38802, 41802, 44802, ..., 65802, 68802, 71802],
 ...,
 [ 38897, 41897, 44897, ..., 65897, 68897, 71897],
 [ 38898, 41898, 44898, ..., 65898, 68898, 71898],
 [ 38899, 41899, 44899, ..., 65899, 68899, 71899]],
 [[ 38900, 41900, 44900, ..., 65900, 68900, 71900],
 [ 38901, 41901, 44901, ..., 65901, 68901, 71901],
 [ 38902, 41902, 44902, ..., 65902, 68902, 71902],
 ...,
 [ 38997, 41997, 44997, ..., 65997, 68997, 71997],
 [ 38998, 41998, 44998, ..., 65998, 68998, 71998],
 [ 38999, 41999, 44999, ..., 65999, 68999, 71999]]],
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 [ 72001, 75001, 78001, ..., 99001, 102001, 105001],
 [ 72002, 75002, 78002, ..., 99002, 102002, 105002],
 ...,
 [ 72097, 75097, 78097, ..., 99097, 102097, 105097],
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 [ 72099, 75099, 78099, ..., 99099, 102099, 105099]],
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 ...,
 [ 72197, 75197, 78197, ..., 99197, 102197, 105197],
 [ 72198, 75198, 78198, ..., 99198, 102198, 105198],
 [ 72199, 75199, 78199, ..., 99199, 102199, 105199]],
 [[ 72200, 75200, 78200, ..., 99200, 102200, 105200],
 [ 72201, 75201, 78201, ..., 99201, 102201, 105201],
 [ 72202, 75202, 78202, ..., 99202, 102202, 105202],
 ...,
 [ 72297, 75297, 78297, ..., 99297, 102297, 105297],
 [ 72298, 75298, 78298, ..., 99298, 102298, 105298],
 [ 72299, 75299, 78299, ..., 99299, 102299, 105299]],
 ...,
 [[ 74700, 77700, 80700, ..., 101700, 104700, 107700],
 [ 74701, 77701, 80701, ..., 101701, 104701, 107701],
 [ 74702, 77702, 80702, ..., 101702, 104702, 107702],
 ...,
 [ 74797, 77797, 80797, ..., 101797, 104797, 107797],
 [ 74798, 77798, 80798, ..., 101798, 104798, 107798],
 [ 74799, 77799, 80799, ..., 101799, 104799, 107799]],
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 [ 74801, 77801, 80801, ..., 101801, 104801, 107801],
 [ 74802, 77802, 80802, ..., 101802, 104802, 107802],
 ...,
 [ 74897, 77897, 80897, ..., 101897, 104897, 107897],
 [ 74898, 77898, 80898, ..., 101898, 104898, 107898],
 [ 74899, 77899, 80899, ..., 101899, 104899, 107899]],
 [[ 74900, 77900, 80900, ..., 101900, 104900, 107900],
 [ 74901, 77901, 80901, ..., 101901, 104901, 107901],
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 ...,
 [ 74997, 77997, 80997, ..., 101997, 104997, 107997],
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 ...,
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 ...,
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 ...,
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 [324198, 327198, 330198, ..., 351198, 354198, 357198],
 [324199, 327199, 330199, ..., 351199, 354199, 357199]],
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 ...,
 [324297, 327297, 330297, ..., 351297, 354297, 357297],
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 [324299, 327299, 330299, ..., 351299, 354299, 357299]],
 ...,
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 ...,
 [326797, 329797, 332797, ..., 353797, 356797, 359797],
 [326798, 329798, 332798, ..., 353798, 356798, 359798],
 [326799, 329799, 332799, ..., 353799, 356799, 359799]],
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 [326801, 329801, 332801, ..., 353801, 356801, 359801],
 [326802, 329802, 332802, ..., 353802, 356802, 359802],
 ...,
 [326897, 329897, 332897, ..., 353897, 356897, 359897],
 [326898, 329898, 332898, ..., 353898, 356898, 359898],
 [326899, 329899, 332899, ..., 353899, 356899, 359899]],
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 [326901, 329901, 332901, ..., 353901, 356901, 359901],
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 ...,
 [326997, 329997, 332997, ..., 353997, 356997, 359997],
 [326998, 329998, 332998, ..., 353998, 356998, 359998],
 [326999, 329999, 332999, ..., 353999, 356999, 359999]]],
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 ...,
 [360097, 363097, 366097, ..., 387097, 390097, 393097],
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 [360099, 363099, 366099, ..., 387099, 390099, 393099]],
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 ...,
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 ...,
 [360297, 363297, 366297, ..., 387297, 390297, 393297],
 [360298, 363298, 366298, ..., 387298, 390298, 393298],
 [360299, 363299, 366299, ..., 387299, 390299, 393299]],
 ...,
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 [362701, 365701, 368701, ..., 389701, 392701, 395701],
 [362702, 365702, 368702, ..., 389702, 392702, 395702],
 ...,
 [362797, 365797, 368797, ..., 389797, 392797, 395797],
 [362798, 365798, 368798, ..., 389798, 392798, 395798],
 [362799, 365799, 368799, ..., 389799, 392799, 395799]],
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 [362801, 365801, 368801, ..., 389801, 392801, 395801],
 [362802, 365802, 368802, ..., 389802, 392802, 395802],
 ...,
 [362897, 365897, 368897, ..., 389897, 392897, 395897],
 [362898, 365898, 368898, ..., 389898, 392898, 395898],
 [362899, 365899, 368899, ..., 389899, 392899, 395899]],
 [[362900, 365900, 368900, ..., 389900, 392900, 395900],
 [362901, 365901, 368901, ..., 389901, 392901, 395901],
 [362902, 365902, 368902, ..., 389902, 392902, 395902],
 ...,
 [362997, 365997, 368997, ..., 389997, 392997, 395997],
 [362998, 365998, 368998, ..., 389998, 392998, 395998],
 [362999, 365999, 368999, ..., 389999, 392999, 395999]]],
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 [396001, 399001, 402001, ..., 423001, 426001, 429001],
 [396002, 399002, 402002, ..., 423002, 426002, 429002],
 ...,
 [396097, 399097, 402097, ..., 423097, 426097, 429097],
 [396098, 399098, 402098, ..., 423098, 426098, 429098],
 [396099, 399099, 402099, ..., 423099, 426099, 429099]],
 [[396100, 399100, 402100, ..., 423100, 426100, 429100],
 [396101, 399101, 402101, ..., 423101, 426101, 429101],
 [396102, 399102, 402102, ..., 423102, 426102, 429102],
 ...,
 [396197, 399197, 402197, ..., 423197, 426197, 429197],
 [396198, 399198, 402198, ..., 423198, 426198, 429198],
 [396199, 399199, 402199, ..., 423199, 426199, 429199]],
 [[396200, 399200, 402200, ..., 423200, 426200, 429200],
 [396201, 399201, 402201, ..., 423201, 426201, 429201],
 [396202, 399202, 402202, ..., 423202, 426202, 429202],
 ...,
 [396297, 399297, 402297, ..., 423297, 426297, 429297],
 [396298, 399298, 402298, ..., 423298, 426298, 429298],
 [396299, 399299, 402299, ..., 423299, 426299, 429299]],
 ...,
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 [398701, 401701, 404701, ..., 425701, 428701, 431701],
 [398702, 401702, 404702, ..., 425702, 428702, 431702],
 ...,
 [398797, 401797, 404797, ..., 425797, 428797, 431797],
 [398798, 401798, 404798, ..., 425798, 428798, 431798],
 [398799, 401799, 404799, ..., 425799, 428799, 431799]],
 [[398800, 401800, 404800, ..., 425800, 428800, 431800],
 [398801, 401801, 404801, ..., 425801, 428801, 431801],
 [398802, 401802, 404802, ..., 425802, 428802, 431802],
 ...,
 [398897, 401897, 404897, ..., 425897, 428897, 431897],
 [398898, 401898, 404898, ..., 425898, 428898, 431898],
 [398899, 401899, 404899, ..., 425899, 428899, 431899]],
 [[398900, 401900, 404900, ..., 425900, 428900, 431900],
 [398901, 401901, 404901, ..., 425901, 428901, 431901],
 [398902, 401902, 404902, ..., 425902, 428902, 431902],
 ...,
 [398997, 401997, 404997, ..., 425997, 428997, 431997],
 [398998, 401998, 404998, ..., 425998, 428998, 431998],
 [398999, 401999, 404999, ..., 425999, 428999, 431999]]]])

>>> pool_size = 4
>>> dmax = np.zeros((pooling_backward_dout.size, pool_size))
>>> dmax.shape
(432000, 4)
>>> pooling_backward_dout.flatten()
array([ 0, 3000, 6000, ..., 425999, 428999, 431999])
>>>