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[Arith] linear system and equation solver #5171

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merged 7 commits into from
Apr 10, 2020
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@yzhliu yzhliu commented Mar 30, 2020

Co-authored-by: Sergei Grechanik sergei.grechanik+h@gmail.com

Linear system data structures and linear equations solver (via Smith Normal Form)

this is part of tensor level autodiff. will be used by #5121

Originally implemented by @sgrechanik-h in #2634 I modified a bit to make it more mathematical. @sgrechanik-h please help to check if the math is correct and whether SuperSimplify is required (I use tir::Simplify instead in this PR, I think it is only required in condition lift)

@sgrechanik-h @tqchen @MarisaKirisame @junrushao1994 @hzfan Please review

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tqchen commented Mar 30, 2020

NOTE: please try to rewrite to directly use the auxiliary class arith::Analyzer instead of the Simplify function, so that the temp data structure can be created only once

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yzhliu commented Mar 31, 2020

@tqchen changed to use arith::Analyzer


/*!
* \brief Represent a linear system including variables, their ranges and
* the linear relations between them (either equations or inequalities)
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I think it's worth mentioning that the system is integer.

Also I'm not sure if LinearSystem is a good name, because it may be useful to have non-linear (in)equalities in relations (which doesn't break the algorithms that work on the linear part).

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good suggestion. how about Formulas, Constraints, RelationSet, IntRelationSet, or InequalitySet (if we make term "inequality" to also include equations)? @sergei-grechanik

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IntegerSet or IntegerSystem maybe?

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sounds good. There's IntSet in tvm, so I'll do IntegerSystem.

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think it a bit more, should we use a more general name? as in solver, we will check the relation and ignore the non-integer equations, which implies it is valid to contain non-integer relations inside. @sergei-grechanik

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If variables are integer, I think it's still ok to call it IntegerSystem. But if we allow non-integer variables (I doubt it is a good idea), then I don't know, Set and System sound too unspecific, Constraints may be ok.

include/tvm/arith/linear_system.h Outdated Show resolved Hide resolved
tests/python/unittest/test_arith_solve_linear_system.py Outdated Show resolved Hide resolved
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About SuperSimplify: it was a combination of the canonical simplifier and the rewriting simplifier that worked best for autodiff (I actually ran it with different combinations and rewrite->canonical->rewrite turned out to be the best, although canonical->rewrite was good too). I think currently the default Simplify function is rewrite->canonical, not sure if this order has a good justification.

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yzhliu commented Apr 1, 2020

@sergei-grechanik do you have example that we have to end with rewrite?

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LGTM, although i have essentially zero expertise in numerical algorithm, so I didnt really understand what is going on.

node->variables = std::move(variables);
node->ranges = std::move(ranges);
node->relations = std::move(relations);
data_ = std::move(node);
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what is data_?

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it's ObjectRef->data_ whose type is ObjectPtr

src/arith/solve_linear_equation.cc Show resolved Hide resolved
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tqchen commented Apr 1, 2020

cc @Hzfengsy @spectrometerHBH @merrymercy please also take a look if you have time, should be relevant to your areas

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@yzhliu Unfortunately I don't have an example. It's written in my notes that "we should end with rw because it factors multipliers out". If it's only that, it's probably not that important.

src/arith/solve_linear_equation.cc Show resolved Hide resolved

// Transform formulas into rows of the matrix
// S_{mxn} V^{-1}_{nxn} x_{nx1} = U y, in which n is # of variables
// here we initialize S_{mxn} to be A, U to be identity matrix.
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V to be identity matrix?

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V was described above. here what I mean is
U^{-1} S V^{-1} x = y = [coefs] => S V^{-1} x = U [coefs]
which implies U is identity.

src/arith/solve_linear_equation.cc Outdated Show resolved Hide resolved
@yzhliu yzhliu force-pushed the linear_solver branch 2 times, most recently from c58057b to c2678f8 Compare April 5, 2020 06:05
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yzhliu commented Apr 5, 2020

@sergei-grechanik I rename it to IntConstraints, and also add checker to ensure the variables to be integers. please take a review again.

* \param V an identity matrix, it will be modified to V_{nxn}
* \param x the x in A x = y. it will be modified to V^{-1}_{nxn} x_{nx1}
* \param y the y in A x = y. it will be modified to U_{mxm} y_{mx1}
*/
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I was thinking about this and came to conclusion that computing the proper Smith normal form may improve stability of automatic differentiation (I mean generating the same gradient code for slightly different but equivalent input code). However, I'm not sure if it's worth it (and not in this PR of course).

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I see. I'll put a todo here.

@yzhliu yzhliu force-pushed the linear_solver branch 2 times, most recently from 3f7424e to 0010a64 Compare April 8, 2020 07:27
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Ok, looks good to me

@tqchen tqchen merged commit e21f268 into apache:master Apr 10, 2020
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tqchen commented Apr 10, 2020

trevor-m pushed a commit to trevor-m/tvm that referenced this pull request Apr 16, 2020
* [arith] linear system and equation solver

Co-authored-by: Sergei Grechanik <sergei.grechanik+h@gmail.com>

* avoid constructing analyzer every time

* generate random test cases and address comments

Co-authored-by: Sergei Grechanik <sergei.grechanik@gmail.com>

* rename linear_system to int_constraints

* add comments and use random seed

* message for reporting failure with seed

* add SEqualReduce to IntConstraints; allow variables & ranges to be None

Co-authored-by: Sergei Grechanik <sergei.grechanik+h@gmail.com>
Co-authored-by: Sergei Grechanik <sergei.grechanik@gmail.com>
zhiics pushed a commit to neo-ai/tvm that referenced this pull request Apr 17, 2020
* [arith] linear system and equation solver

Co-authored-by: Sergei Grechanik <sergei.grechanik+h@gmail.com>

* avoid constructing analyzer every time

* generate random test cases and address comments

Co-authored-by: Sergei Grechanik <sergei.grechanik@gmail.com>

* rename linear_system to int_constraints

* add comments and use random seed

* message for reporting failure with seed

* add SEqualReduce to IntConstraints; allow variables & ranges to be None

Co-authored-by: Sergei Grechanik <sergei.grechanik+h@gmail.com>
Co-authored-by: Sergei Grechanik <sergei.grechanik@gmail.com>
dpankratz pushed a commit to dpankratz/incubator-tvm that referenced this pull request Apr 24, 2020
* [arith] linear system and equation solver

Co-authored-by: Sergei Grechanik <sergei.grechanik+h@gmail.com>

* avoid constructing analyzer every time

* generate random test cases and address comments

Co-authored-by: Sergei Grechanik <sergei.grechanik@gmail.com>

* rename linear_system to int_constraints

* add comments and use random seed

* message for reporting failure with seed

* add SEqualReduce to IntConstraints; allow variables & ranges to be None

Co-authored-by: Sergei Grechanik <sergei.grechanik+h@gmail.com>
Co-authored-by: Sergei Grechanik <sergei.grechanik@gmail.com>
monklof pushed a commit to monklof/incubator-tvm that referenced this pull request Jan 22, 2021
…m_data:master to master

* commit 'cd0d52daa6942bdafa9363ff6cfa3d25fcd5b8d6': (824 commits)
  [Intrinsic] Add log1p, ldexp, atan2, hypot, nextafter, copysign (apache#5312)
  [Rust][CI] Restore Rust CI (apache#5137)
  Remove PrimExpr from String (apache#5311)
  [Requantize] Cleanup and Optimize Lowering (apache#5286)
  [IR][TRANSFORM] Enable CopyOnWrite for passes. (apache#5309)
  [PYTORCH]Abs, Arange, Softplus ops (apache#5295)
  [LLVM] Fix generation of LLVM intrinsics (apache#5282)
  [BYOC] Add example of Composite + Annotate for DNNL fused op (apache#5272)
  [Frontend][TensorFlow]Improve TensorFlow Static Shape Tensor Array (apache#5243)
  [RUNTIME] Introduce RValue reference(move) support to TypedPackedFunc (apache#5271)
  [RELAY][FRONTEND][CAFFE2] add Mul and ConvTranspose operator (apache#5302)
  [BYOC] Refine AnnotateTarget and MergeCompilerRegion Passes (apache#5277)
  [CI] Fix the hexagon string (apache#5304)
  [Arith] linear system and equation solver (apache#5171)
  [PYTORCH]Repeat, Reciprocal & Reshape Op support (apache#5280)
  [FRONTEND][TENSORFLOW] Fix gather_nd indices (apache#5279)
  Update device_annotation.cc (apache#5291)
  [REFACTOR][IR] Move to runtime::String (apache#5276)
  [NDArray] Set shape_ in NDArray::FromDLPack (apache#5301)
  [RUNTIME] Initial implementation of Hexagon runtime support (apache#5252)
  ...
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