Convert Inception v3 batch-normalized weights into weights and biases for MPSCNNConvolution.
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LICENSE initial commit Oct 28, 2016 initial commit Oct 28, 2016 initial commit Oct 28, 2016
prediction_comparison.txt initial commit Oct 28, 2016

Generating weights and biases for MPSCNNConvolution

Converts Inception v3 batch-normalized weights into weights and biases for MPSCNNConvolution.


The generated weights and biases are close to the weights included in the MetalImageRecognition sample code. The max delta for the weights and biases are listed below.

conv                                     [max delta: w=0.000406 b=0.000037]
conv_1                                   [max delta: w=0.000016 b=0.000040]
conv_2                                   [max delta: w=0.000005 b=0.000022]
conv_3                                   [max delta: w=0.000010 b=0.000014]
conv_4                                   [max delta: w=0.000008 b=0.000013]
mixed_conv                               [max delta: w=0.000006 b=0.000009]
mixed_tower_conv                         [max delta: w=0.000007 b=0.000012]
mixed_tower_conv_1                       [max delta: w=0.000005 b=0.000007]
mixed_tower_1_conv                       [max delta: w=0.000013 b=0.000062]
mixed_tower_1_conv_1                     [max delta: w=0.000014 b=0.000048]
mixed_tower_1_conv_2                     [max delta: w=0.000018 b=0.000033]
mixed_tower_2_conv                       [max delta: w=0.000021 b=0.000042]
mixed_1_conv                             [max delta: w=0.000007 b=0.000015]
mixed_1_tower_conv                       [max delta: w=0.000010 b=0.000013]
mixed_1_tower_conv_1                     [max delta: w=0.000008 b=0.000008]
mixed_1_tower_1_conv                     [max delta: w=0.000017 b=0.000020]
mixed_1_tower_1_conv_1                   [max delta: w=0.000013 b=0.000030]
mixed_1_tower_1_conv_2                   [max delta: w=0.000011 b=0.000019]
mixed_1_tower_2_conv                     [max delta: w=0.000031 b=0.000074]
mixed_2_conv                             [max delta: w=0.000008 b=0.000012]
mixed_2_tower_conv                       [max delta: w=0.000013 b=0.000025]
mixed_2_tower_conv_1                     [max delta: w=0.000006 b=0.000009]
mixed_2_tower_1_conv                     [max delta: w=0.000012 b=0.000025]
mixed_2_tower_1_conv_1                   [max delta: w=0.000008 b=0.000015]
mixed_2_tower_1_conv_2                   [max delta: w=0.000008 b=0.000010]
mixed_2_tower_2_conv                     [max delta: w=0.000034 b=0.000042]
mixed_3_conv                             [max delta: w=0.000010 b=0.000018]
mixed_3_tower_conv                       [max delta: w=0.000013 b=0.000020]
mixed_3_tower_conv_1                     [max delta: w=0.000013 b=0.000022]
mixed_3_tower_conv_2                     [max delta: w=0.000022 b=0.000031]
mixed_4_conv                             [max delta: w=0.000010 b=0.000021]
mixed_4_tower_conv                       [max delta: w=0.000010 b=0.000014]
mixed_4_tower_conv_1                     [max delta: w=0.000011 b=0.000015]
mixed_4_tower_conv_2                     [max delta: w=0.000011 b=0.000015]
mixed_4_tower_1_conv                     [max delta: w=0.000019 b=0.000025]
mixed_4_tower_1_conv_1                   [max delta: w=0.000015 b=0.000021]
mixed_4_tower_1_conv_2                   [max delta: w=0.000016 b=0.000016]
mixed_4_tower_1_conv_3                   [max delta: w=0.000016 b=0.000021]
mixed_4_tower_1_conv_4                   [max delta: w=0.000014 b=0.000025]
mixed_4_tower_2_conv                     [max delta: w=0.000031 b=0.000089]
mixed_5_conv                             [max delta: w=0.000012 b=0.000013]
mixed_5_tower_conv                       [max delta: w=0.000017 b=0.000025]
mixed_5_tower_conv_1                     [max delta: w=0.000022 b=0.000020]
mixed_5_tower_conv_2                     [max delta: w=0.000013 b=0.000019]
mixed_5_tower_1_conv                     [max delta: w=0.000017 b=0.000022]
mixed_5_tower_1_conv_1                   [max delta: w=0.000019 b=0.000022]
mixed_5_tower_1_conv_2                   [max delta: w=0.000014 b=0.000019]
mixed_5_tower_1_conv_3                   [max delta: w=0.000014 b=0.000018]
mixed_5_tower_1_conv_4                   [max delta: w=0.000012 b=0.000017]
mixed_5_tower_2_conv                     [max delta: w=0.000032 b=0.000051]
mixed_6_conv                             [max delta: w=0.000011 b=0.000014]
mixed_6_tower_conv                       [max delta: w=0.000019 b=0.000025]
mixed_6_tower_conv_1                     [max delta: w=0.000031 b=0.000022]
mixed_6_tower_conv_2                     [max delta: w=0.000016 b=0.000023]
mixed_6_tower_1_conv                     [max delta: w=0.000014 b=0.000027]
mixed_6_tower_1_conv_1                   [max delta: w=0.000026 b=0.000037]
mixed_6_tower_1_conv_2                   [max delta: w=0.000018 b=0.000023]
mixed_6_tower_1_conv_3                   [max delta: w=0.000018 b=0.000031]
mixed_6_tower_1_conv_4                   [max delta: w=0.000018 b=0.000051]
mixed_6_tower_2_conv                     [max delta: w=0.000026 b=0.000034]
mixed_7_conv                             [max delta: w=0.000012 b=0.000017]
mixed_7_tower_conv                       [max delta: w=0.000017 b=0.000023]
mixed_7_tower_conv_1                     [max delta: w=0.000027 b=0.000034]
mixed_7_tower_conv_2                     [max delta: w=0.000020 b=0.000030]
mixed_7_tower_1_conv                     [max delta: w=0.000020 b=0.000027]
mixed_7_tower_1_conv_1                   [max delta: w=0.000027 b=0.000027]
mixed_7_tower_1_conv_2                   [max delta: w=0.000015 b=0.000026]
mixed_7_tower_1_conv_3                   [max delta: w=0.000015 b=0.000023]
mixed_7_tower_1_conv_4                   [max delta: w=0.000014 b=0.000030]
mixed_7_tower_2_conv                     [max delta: w=0.000025 b=0.000039]
mixed_8_tower_conv                       [max delta: w=0.000096 b=0.000074]
mixed_8_tower_conv_1                     [max delta: w=0.000046 b=0.000093]
mixed_8_tower_1_conv                     [max delta: w=0.000094 b=0.000088]
mixed_8_tower_1_conv_1                   [max delta: w=0.000020 b=0.000038]
mixed_8_tower_1_conv_2                   [max delta: w=0.000016 b=0.000034]
mixed_8_tower_1_conv_3                   [max delta: w=0.000026 b=0.000064]
mixed_9_conv                             [max delta: w=0.000023 b=0.000030]
mixed_9_tower_conv                       [max delta: w=0.000020 b=0.000028]
mixed_9_tower_mixed_conv                 [max delta: w=0.000038 b=0.000065]
mixed_9_tower_mixed_conv_1               [max delta: w=0.000044 b=0.000059]
mixed_9_tower_1_conv                     [max delta: w=0.000019 b=0.000031]
mixed_9_tower_1_conv_1                   [max delta: w=0.000016 b=0.000025]
mixed_9_tower_1_mixed_conv               [max delta: w=0.000025 b=0.000063]
mixed_9_tower_1_mixed_conv_1             [max delta: w=0.000026 b=0.000064]
mixed_9_tower_2_conv                     [max delta: w=0.000026 b=0.000043]
mixed_10_conv                            [max delta: w=0.000385 b=0.000087]
mixed_10_tower_conv                      [max delta: w=0.000059 b=0.000101]
mixed_10_tower_mixed_conv                [max delta: w=0.000436 b=0.000089]
mixed_10_tower_mixed_conv_1              [max delta: w=0.000492 b=0.000091]
mixed_10_tower_1_conv                    [max delta: w=0.000035 b=0.000059]
mixed_10_tower_1_conv_1                  [max delta: w=0.000029 b=0.000055]
mixed_10_tower_1_mixed_conv              [max delta: w=0.000100 b=0.000048]
mixed_10_tower_1_mixed_conv_1            [max delta: w=0.000155 b=0.000050]
mixed_10_tower_2_conv                    [max delta: w=0.000045 b=0.000027]
softmax                                  [max delta: w=0.000005 b=0.000005]

The predictions between the Tensorflow Batch-Normalized model, the original model and the generated model are close but not exact. A comparison of 1000 ImageNet images is included in prediction_comparison.txt. The top-1 and top-5 error rates for the original and generated models (vs the Tensorflow Batch-Normalized model) are:

Original  Top-1: 24.6%
Generated Top-1: 24.3%
Original  Top-5:  4.2%
Generated Top-5:  4.2%



Basic usage:


will download the Inception v3 weights into the input directory and generate weights and biases in the output directory. The file format follows the MetalImageRecognition sample code.

If you want to compare the generated values to the MetalImageRecognition values:

./ --dat-dir=[path to MetalImageRecognition .dat files]

Other options:

  • --help: Display the help message.
  • --inception3-url: Inception v3 model URL.
  • --input-dir: Directory to download the Inception v3 model.
  • --output-dir: Directory to generate weights and biases.
  • --dat-dir: Directory of MetalImageRecognition .dat files.

Implementation Details

Apple's MetalImageRecognition README provides this note for converting batch-normalized weights into weights and biases:

The weights for this particular network were batch normalized but for inference we may use :

w = 𝛄 / √(s + 0.001), b = ß - ( A * m )

s: variance
m: mean
𝛄: gamma
ß: beta

w: weights of a feature channel
b: bias of a feature channel 

for every feature channel separately to get the corresponding weights and biases

In the paper 'Batch Normalization: Accelerating Deep Network Training by Reducing Internal Covariate Shift' by Sergey Ioffe and Christian Szegedy (, we can use Algorithm 2, Output, Step 11 to derive:

Weight = \frac{\gamma}{\sqrt{Var[x]+0.001}} * Weight_{BN}

Bias = \beta - (\frac{\gamma}{\sqrt{Var[x]+0.001}})*E[x]