A few MobileNetV3 tweaks

* fix expansion ratio on early block
* change comment re stride mistake in paper
* fix rounding not being called properly for all multipliers != 1.0

models/genmobilenet.py

@@ -285,7 +285,7 @@ class _BlockBuilder:
     def _make_block(self, ba):
         bt = ba.pop('block_type')
         ba['in_chs'] = self.in_chs
-        ba['out_chs'] = _round_channels(ba['out_chs'])
+        ba['out_chs'] = self._round_channels(ba['out_chs'])
         ba['bn_momentum'] = self.bn_momentum
         ba['bn_eps'] = self.bn_eps
         ba['folded_bn'] = self.folded_bn
@@ -676,6 +676,7 @@ class GenMobileNet(nn.Module):
             # efficient head, currently only mobilenet-v3 performs pool before last 1x1 conv
             x = self.global_pool(x)  # always need to pool here regardless of bool
             x = self.conv_head(x)
+            # no BN
             x = self.act_fn(x)
             if pool:
                 # expect flattened output if pool is true, otherwise keep dim
@@ -884,7 +885,7 @@ def _gen_mobilenet_v3(depth_multiplier, num_classes=1000, **kwargs):
         # stage 0, 112x112 in
         ['ds_r1_k3_s1_e1_c16_are_noskip'],  # relu
         # stage 1, 112x112 in
-        ['ir_r1_k3_s2_e4_c24_are', 'ir_r1_k3_s1_e6_c24_are'],  # relu
+        ['ir_r1_k3_s2_e4_c24_are', 'ir_r1_k3_s1_e3_c24_are'],  # relu
         # stage 2, 56x56 in
         ['ir_r3_k5_s2_e3_c40_se0.25_are'],  # relu
         # stage 3, 28x28 in
@@ -893,9 +894,10 @@ def _gen_mobilenet_v3(depth_multiplier, num_classes=1000, **kwargs):
         # stage 4, 14x14in
         ['ir_r2_k3_s1_e6_c112_se0.25'],  # hard-swish
         # stage 5, 14x14in
-        # FIXME the paper contains a weird block-stride pattern 1-2-1 that doesn't fit the usual 2-1-...
-        # What is correct?
-        ['ir_r3_k5_s2_e6_c160_se0.25'],  # hard-swish
+        # FIXME paper has a mistaken block-stride pattern 1-2-1 that doesn't fit the usual 2-1-..., ignoring
+        # The paper numbers result in an exp factor of 4.2 in the middle of this block, but keeping at 6
+        # results in a param count closer to 5.4m
+        ['ir_r1_k5_s2_e6_c160_se0.25', 'ir_r1_k5_s1_e6_c160_se0.25', 'ir_r1_k5_s1_e6_c160_se0.25'],  # hard-swish
         # stage 6, 7x7 in
         ['cn_r1_k1_s1_c960'],  # hard-swish
     ]