98 lines
2.7 KiB
Python
98 lines
2.7 KiB
Python
import numpy as np
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def tensor(*args, **kwargs):
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return Tensor(*args, **kwargs)
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class Tensor:
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# TODO Implement 'requires_grad' functionality.
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def __init__(self, value):
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# NOTE We technically could support both numpy arrays and scalar values,
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# but it is too much work.
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if not isinstance(value, np.ndarray):
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print(f"{type(value)} is not compatible with {np.ndarray}")
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exit(-1)
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self.value = value
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self.grad = np.zeros_like(value)
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# Required for backprop.
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self._parents = None
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self._back = None
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# uwu literally the only place where I have type annotations
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def __repr__(self) -> str:
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return f"Tensor(value={self.value}, grad={self.grad})"
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# Save values for the backward pass.
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def _save(self, *args):
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self._parents = args
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# TODO Maybe refactor the functions system? Maybe something like pytorch/tinygrad?
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def add(self, other):
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tensor = Tensor(np.add(self.value, other.value))
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tensor._save(self, other)
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def back(upstream):
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return np.dot(np.ones_like(self.value).T, upstream), np.dot(np.ones_like(self.value).T, upstream)
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tensor._back = back
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return tensor
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def mul(self, other):
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tensor = Tensor(np.dot(self.value, other.value))
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tensor._save(self, other)
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def back(upstream):
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a, b = tensor._parents
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return np.dot(b.value, upstream), np.dot(a.value.T, upstream)
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tensor._back = back
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return tensor
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def expt(self, exponent):
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tensor = Tensor(self.value ** exponent)
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tensor._save(self)
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def back(upstream):
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a, = tensor._parents
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return [np.dot(exponent * (a.value ** (exponent - 1)), upstream)]
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tensor._back = back
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return tensor
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def reciprocal(self):
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tensor = Tensor(1.0 / self.value)
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tensor._save(self)
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def back(upstream):
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a, = tensor._parents
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return [np.dot(-1.0 / (a.value ** 2), upstream)]
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tensor._back = back
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return tensor
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def exp(self):
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tensor = Tensor(np.exp(self.value))
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tensor._save(self)
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def back(upstream):
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a, = tensor._parents
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return [np.dot(np.exp(a.value), upstream)]
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tensor._back = back
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return tensor
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# TODO Compute gradients only for tensors that need it.
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def _backprop(self, upstream):
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# Backprop through the tensor iff it has any parents.
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if self._parents is not None:
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for node, grad in zip(self._parents, self._back(upstream)):
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# Set the node gradient to the computed gradient.
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node.grad = grad
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# Iterate through all (possible) parent nodes of this node.
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node._backprop(grad)
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def backward(self):
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# Partial of self with respect to self is ALWAYS 1.
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self.grad = np.ones_like(self.value)
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self._backprop(self.grad)
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