Trait MPSImageSizeEncodingState

Source

pub unsafe trait MPSImageSizeEncodingState: NSObjectProtocol {
    // Provided methods
    unsafe fn sourceWidth(&self) -> NSUInteger
       where Self: Sized + Message { ... }
    unsafe fn sourceHeight(&self) -> NSUInteger
       where Self: Sized + Message { ... }
}

Available on crate feature MPSNeuralNetworkTypes only.

Expand description

MPSStates conforming to this protocol contain information about a image size elsewhere in the graph

In some graphs a sequence of operations are done, then they are undone ins a series of ‘reverse’ operations. Examples might be pooling vs pooling gradient / upsampling, or convolution vs. convolution transpose. In such cases, the ‘reverse’ pass generally is converting from a smaller image to a larger image, and there is insufficient information to do this correctly. Several answers exist and we don’t know which is correct.

As an example, consider trying to ‘undo’ integer division with a multiplication. The expression c = a/b is incomplete because there is also a remainder, which may constitute information lost. If we want to reconstitute a based on c and b, we need to use a = c * b + remainder, not just a = cb. Similarly, when undoing a downsizing operation, we need the original size to find which answer in the range of a = cb + [0,b-1] is the right one.