XORTRAN
XORTRAN is a multilayer perceptron (MLP) written in FORTRAN IV, compiled and executed under RT-11 on a PDP-11/34A (via SIMH simulator).
It learns the classic non-linear XOR problem using:
One hidden layer (4 neurons, leaky ReLU activation)
Backpropagation with mean squared error loss
He-like initialization (manual Gaussian via Box-Muller lite)
Learning rate annealing (0.5 → 0.1 → 0.01)
Tanh output
The code compiles with the DEC FORTRAN IV compiler (1974). Execution requires a system with at least 32 kilobytes of memory and an FP11 floating-point processor. The PDP-11/34A was chosen as it was the smallest and most affordable PDP-11 equipped with an FP11 floating-point processor in the 1970s.
The training of the 17 parameters should take less than a couple minutes on the real hardware. In SIMH, setting the throttle to 500K ( set throttle 500K ) will provide a more realistic execution speed.
... continue reading