Calculate Output Volume

Problem Statement

Calculate the spatial dimensions of a convolutional layer output.

Background

The output size $O$ of a convolutional layer is determined by input size $I$, filter size $F$, padding $P$, and stride $S$ using the formula:

$O = \lfloor \frac{I - F + 2P}{S} \rfloor + 1$

If the filter is larger than the padded input (i.e., $I - F + 2P < 0$), the configuration is invalid.

Your Task

Write a function conv_output_size(input_size, filter_size, padding, stride) that returns the output dimension. If the configuration is invalid (filter larger than padded input), return -1.

Output Format

Return an integer representing the output dimension, or -1 if invalid.