Eliminate scratch memory used when generating contexts #557
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apoelstra
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Concept ACK. Are you going to batch that extra inv? |
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Yep, done. |
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@sipa can you take a look at this? |
apoelstra
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Replaced all instances of |
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Needs rebase on #553 (not urgent, I'll review soon rebased or not). |
apoelstra
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Rebased. |
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Addressed all comments. |
apoelstra
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ACK, please squash the fixes in the respective commits? It's a really cool trick; I hadn't expected it would be possible to reconstruct everything from Y and Z-ratios, but the formulas work out. It seems this actually makes |
apoelstra
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Squashed. |
apoelstra
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I think it's a bit easier to understand if the z-ratios are stored with the y-values that they'll be used with (instead of off by 1). Like this: peterdettman@f1ab49c |
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I think @peterdettman's commit is great, it does simplify the logic a fair bit. |
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Added both of Peter's commits squashed into one, and an addition commit that adds even more comments explaining how the effective-affine isomorphic curve plays into everything. @peterdettman do you think this is better? @sipa can you comment on this? We're back to "working backward" in the sense that I do a series of equations starting from abstract coordinates and ending up with values that have variable bindings, but it's all pretty explicit now. |
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apoelstra
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@apoelstra Looks very readable now; I'll review in detail soon. |
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Yes, better, thanks for improving that. |
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Nice! |
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utACK b3bf5f9 |
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Ready for merge? |
b3bf5f9 ecmult_impl: expand comment to explain how effective affine interacts with everything (Andrew Poelstra) efa783f Store z-ratios in the 'x' coord they'll recover (Peter Dettman) ffd3b34 add `secp256k1_ge_set_all_gej_var` test which deals with many infinite points (Andrew Poelstra) 84740ac ecmult_impl: save one fe_inv_var (Andrew Poelstra) 4704527 ecmult_impl: eliminate scratch memory used when generating context (Andrew Poelstra) 7f7a2ed ecmult_gen_impl: eliminate scratch memory used when generating context (Andrew Poelstra) Pull request description: Builds on #553 Tree-SHA512: 6031a601a4a476c1d21fc8db219383e7930434d2f199543c61aca0118412322dd814a0109c385ff1f83d16897170dd0c25051697b0f88f15234b0059b661af41
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Addition/subtraction with constants are effectively free except sometimes in the tightest of loops, the compiler will usually remove them, when it doesn't they usually get hidden by pipelines. This code is run-once code, it should be optimized for clarity and maintainability most and testability much more than for size (within reason) and performance. |
0522caa Explain caller's obligations for preallocated memory (Tim Ruffing) 238305f Move _preallocated functions to separate header (Tim Ruffing) 695feb6 Export _preallocated functions (Tim Ruffing) 814cc78 Add tests for contexts in preallocated memory (Tim Ruffing) ba12dd0 Check arguments of _preallocated functions (Tim Ruffing) 5feadde Support cloning a context into preallocated memory (Tim Ruffing) c4fd5da Switch to a single malloc call (Tim Ruffing) ef020de Add size constants for preallocated memory (Tim Ruffing) 1bf7c05 Prepare for manual memory management in preallocated memory (Tim Ruffing) Pull request description: @apoelstra This builds on #557. Manually managing memory is always a pain in the ass in some way. I tried to keep the pain manageable. I'm open to suggestions to make this less ugly or error-prone. to do: * tests * export functions ACKs for commit 0522ca: Tree-SHA512: 8ddb5b70219b6f095e780a9812d2387ab2a7f399803ce4101e27da504b479a61ebe08b6380568c7ba6f1e73d7d0b1f58a3c0a66fa0fdec7a64cd0740e156ce38
Builds on #553