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Stop pre-constructing reverse-mode tape blocks, and reuse them after a rewind - #1625
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…a rewind Blocks are raw storage now, so a second-order tape adds no leaves to the first-order tape, and a rewound tape refills its blocks instead of allocating new ones. Documents that rvar copies share a node. Closes #1624 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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thanks, i'll take a look at this tomorrow |
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Blocks are raw storage now, so a second-order tape adds no leaves to the first-order tape,
and a rewound tape refills its blocks instead of allocating new ones. Documents that rvar copies share a node.
Closes #1624
Rewinding now destroys the discarded elements, so the blocks no longer have to do it.
get_active_tape<double, 2>()gradofx*x*y + sin(y)after thatApple M-series, clang -O2; the reproducers are in #1624. The reverse-mode and gradient-optimizer tests pass, also under ASan/UBSan.
@demroz, this changes your allocator; would you take a look?
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