A computation graph remembers one forward value per block, and the backward pass reads each stored value once and frees it.
Question: What does the computer remember?
Re-simulated Re-simulated: every node value, slot count and stage is computed exactly by data/scripts/c18.s04.L1.py from h_l = tanh(1.3 h_{l-1} + 0.1) with h_0 = 0.7, and nothing is measured from a source. The frames step through the forward pass, which stores one value per block, and the backward pass, which reads each stored value once and frees its slot. The depth control runs from 2 to 12 blocks: at the default 8 the bar fills 8 slots and empties them in 8 backward reads, and at 12 it peaks at 12.
Frame 1 of 17: Idle: nothing storedNothing is stored yet. The graph is labels and edges. Press play, or step forward, to run the forward pass. This chain has 8 blocks, so the peak occupancy will be 8 slots.
Idle: nothing stored. Nothing is stored yet. The graph is labels and edges. Press play, or step forward, to run the forward pass. This chain has 8 blocks, so the peak occupancy will be 8 slots.
Keyboard: Space plays or pauses, Left and Right step, Home goes to the first frame, End goes to the last frame.
Text description of this lab
A chain of rounded blocks runs left to right from input to output. In the forward pass each block lights in turn and adds its computed number to a memory bar below, one slot per block, until eight slots are filled; at twelve blocks, twelve slots. The sweep then reverses: blocks light right to left, each reads its stored number and empties its slot, until the bar is empty. A readout prints the stage, the slots held, and the peak.