XavierFilller and MSRAFiller fail to fill a bias blob

[ghostsun89]

Issue summary

XavierFilller and MSRAFiller doesn't work in current master, the error info as below:

I0305 17:03:08.437372  6693 net.cpp:88] Creating Layer conv1
I0305 17:03:08.437381  6693 net.cpp:410] conv1 <- data
I0305 17:03:08.437389  6693 net.cpp:384] conv1 -> conv1
F0305 17:03:08.437960  6693 blob.hpp:122] Check failed: axis_index < num_axes() (1 vs. 1) axis 1 out of range for 1-D Blob with shape 64 (64)

Steps to reproduce

run a caffe prototxt with Convolution, which para filler use Xavier or MSRA.
I ran a Resnet50 prototxt. Part as follow:

layer {
	bottom: "data"
	top: "conv1"
	name: "conv1"
	type: "Convolution"
	convolution_param {
		num_output: 64
		kernel_size: 7
		pad: 3
		stride: 2
                weight_filler {
                  type: "msra"
                }
                bias_filler {
                  type: "msra"
                }
	}
}

[Noiredd]

I can reproduce this behavior. Looks like the bias_filler causes the issue whenever it's set to "msra" or "xavier". If I checkout the commit b3deb95 (right before merging #6240) the problems disappear.

Turns out prior to #6240 when we used Blob::channels (see line 151) on a 1-D blob, it returned 1. Current implementation uses Blob::shape, which makes the following check, erroring out if we request shape(1) of a 1-D blob. Fix would be to safeguard the call to shape - I will push it tomorrow, unless you want to beat me to it.

On the other hand, maybe we should add a bias filler check too, to make sure we catch this next time.

[ghostsun89]

@Noiredd Thanks a lot.

[Noiredd]

To be honest, using Xavier/MSRA for bias initialization does not make much sense: how to define fan_in and fan_out for it? Still, we shouldn't be throwing errors in this case - fix is on its way.