On-the-fly net resizing, without reallocation (where possible) #594

This is in keeping with BVLC#742.

This allows nets to be reshaped very quickly (essentially for free) as long as sufficient memory has been allocated. Calling Blob::Reshape in order to free up memory becomes impossible; however, this is not a normal use case (and deleting blobs does free memory).

Note that calling Reshape when no reshape is necessary should be effectively a no-op, so this is not a performance regression.

This will make it possible to add reshaping to cuDNN layers.

Note that we are dropping some checks from LRN layer. However, these checks are fairly redundant; something is very wrong if these layers are producing top blobs that are different sizes than their inputs, and tests are the right place to catch that. The thing that really should be checked (that isn't) is that that local_size needs to be odd; this will be added in a future commit.

Strictly speaking, Reshape doesn't need to be called until the first Forward call; however, much existing code (especially tests) assumes that top blobs will be set up in SetUp, so we may as well do it there.

Now that top blobs are set up in Layer::Reshape, it's Reshape that is mandatory, and simple layers often don't need to implement LayerSetUp. Reshape is (already) declared abstract, so not implementing it is a compile-time error.

Since we are now calling Reshape in the Forward pass, it's only fair to include it when timing. Reshape calls should normally be four or so orders of magnitude faster than Forward calls; this change also makes it easy to notice a mistake that causes something slow to happen in Reshape.

Note that it is not normally necessary to call this function when using reshapable nets, but sometimes it can be useful to compute the sizes of intermediate layers without waiting for the forward pass.

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On-the-fly net resizing, without reallocation (where possible) #594

On-the-fly net resizing, without reallocation (where possible) #594

Commits on Sep 18, 2014