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use mv in ComposedLinearOperator.as_matrix to avoid unecessary materialisation #196

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use mv in ComposedLinearOperator.as_matrix to avoid unecessary materialisation #196

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da6af45
Optimize ComposedLinearOperator materialisation and as_matrix
jpbrodrick89 Jan 31, 2026
0cfecac
Merge branch 'main' into jpb/composed-materialise
jpbrodrick89 Feb 2, 2026
b13d829
run precommit
jpbrodrick89 Feb 2, 2026
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24 changes: 19 additions & 5 deletions lineax/_operator.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1148,12 +1148,20 @@ def mv(self, vector):
return self.operator1.mv(self.operator2.mv(vector))

def as_matrix(self):
return jnp.matmul(
self.operator1.as_matrix(),
self.operator2.as_matrix(),
precision=lax.Precision.HIGHEST, # pyright: ignore
if isinstance(self.operator1, IdentityLinearOperator):
return self.operator2.as_matrix()
if isinstance(self.operator2, IdentityLinearOperator):
return self.operator1.as_matrix()
_, unravel = eqx.filter_eval_shape(
jfu.ravel_pytree, self.operator1.in_structure()
)

def mv_flat(v):
out = self.operator1.mv(unravel(v))
return jfu.ravel_pytree(out)[0]

return jax.vmap(mv_flat, in_axes=1, out_axes=1)(self.operator2.as_matrix())

def transpose(self):
return self.operator2.transpose() @ self.operator1.transpose()

Expand Down Expand Up @@ -1939,7 +1947,13 @@ def _(operator):

@materialise.register(ComposedLinearOperator)
def _(operator):
return materialise(operator.operator1) @ materialise(operator.operator2)
op1 = materialise(operator.operator1)
op2 = materialise(operator.operator2)
if isinstance(op1, IdentityLinearOperator):
return op2
if isinstance(op2, IdentityLinearOperator):
return op1
return op1 @ op2


@diagonal.register(ComposedLinearOperator)
Expand Down
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