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torch-mlir/lib/Conversion/TorchToLinalg/Random.cpp

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Also available under a BSD-style license. See LICENSE.
//
//===----------------------------------------------------------------------===//
#include "torch-mlir/Conversion/TorchToLinalg/TorchToLinalg.h"
#include "PopulatePatterns.h"
#include "mlir/Dialect/Arith/IR/Arith.h"
#include "mlir/Dialect/Linalg/IR/Linalg.h"
#include "mlir/Dialect/SCF/IR/SCF.h"
#include "mlir/IR/Matchers.h"
#include "torch-mlir/Conversion/TorchToLinalg/Utils.h"
#include "torch-mlir/Conversion/Utils/Utils.h"
#include "torch-mlir/Dialect/Torch/IR/TorchOps.h"
#include "torch-mlir/Dialect/Torch/Utils/TorchUpstream.h"
#include "torch-mlir/Dialect/TorchConversion/IR/TorchConversionOps.h"
using namespace mlir;
using namespace mlir::torch;
using namespace mlir::torch::Torch;
namespace {
// TODO: Dropout should probably be handled in DecomposeComplexOps instead of
// here.
class ConvertAtenDropoutOp : public OpConversionPattern<AtenDropoutOp> {
public:
using OpConversionPattern::OpConversionPattern;
LogicalResult
matchAndRewrite(AtenDropoutOp op, OpAdaptor adaptor,
ConversionPatternRewriter &rewriter) const override {
if (failed(verifyLinalgCompatibleTypes(op, rewriter)))
return failure();
bool train;
if (!matchPattern(op.getTrain(), m_TorchConstantBool(&train)))
return rewriter.notifyMatchFailure(op,
"Expected train to be constant bool.");
if (train)
return failure();
auto resultType = cast<RankedTensorType>(
getTypeConverter()->convertType(op->getResult(0).getType()));
rewriter.replaceOpWithNewOp<tensor::CastOp>(op, resultType,
adaptor.getInput());
return success();
}
};
} // namespace
static Value toLinearIndex(OpBuilder &b, Location loc,
ArrayRef<Value> indicesIntValues,
ArrayRef<Value> shapeIntValues) {
assert(indicesIntValues.size() == shapeIntValues.size() &&
"Expected `indices` and `shape` to have the same size");
Value result =
b.create<arith::ConstantOp>(loc, b.getZeroAttr(b.getI64Type()));
for (auto [index, stride] : llvm::zip(indicesIntValues, shapeIntValues)) {
assert(isa<mlir::IntegerType>(index.getType()) &&
isa<mlir::IntegerType>(stride.getType()) &&
"Input arrays to `toLinearIndex` must only contain values of type "
"`mlir::IntegerType`");
Value mul = b.create<arith::MulIOp>(loc, result, stride);
result = b.create<arith::AddIOp>(loc, mul, index);
}
return result;
}
// Squares64 Algorithm for generating 64-bit random numbers.
// See: https://arxiv.org/abs/2004.06278
static Value randomUniformUInt(OpBuilder &b, Location loc, Value ctr,
Value key) {
auto mul = [&](Value lhs, Value rhs) -> Value {
return b.create<arith::MulIOp>(loc, lhs, rhs);
};
auto add = [&](Value lhs, Value rhs) -> Value {
return b.create<arith::AddIOp>(loc, lhs, rhs);
};
Value cst32 = b.create<arith::ConstantOp>(loc, b.getI64IntegerAttr(32));
auto shiftRight32 = [&](Value val) -> Value {
return b.create<arith::ShRUIOp>(loc, val, cst32);
};
auto swapLoHi = [&](Value val) -> Value {
Value leftShift = b.create<arith::ShLIOp>(loc, val, cst32);
Value rightShift = shiftRight32(val);
return b.create<arith::OrIOp>(loc, leftShift, rightShift);
};
auto bitwiseXOr = [&](Value lhs, Value rhs) -> Value {
return b.create<arith::XOrIOp>(loc, lhs, rhs);
};
Value t, x, y, z;
x = mul(ctr, key);
y = x;
z = add(y, key);
x = add(mul(x, x), y);
x = swapLoHi(x);
x = add(mul(x, x), z);
x = swapLoHi(x);
x = add(mul(x, x), y);
x = swapLoHi(x);
t = x = add(mul(x, x), z);
x = swapLoHi(x);
return bitwiseXOr(t, shiftRight32(add(mul(x, x), y)));
}
// generate uniform random Float64
static Value randomUniformF64(OpBuilder &b, Location loc, Value ctr, Value key,
Value min, Value max) {
Value randomVal = randomUniformUInt(b, loc, ctr, key);
// scale = (max - min) * const(F64, 5.4210108E-20)
// which is derived from rand(min,max) =
// rand()/(RAND_MAX/(max-min)) where RAND_MAX = 2^64 - 1
Value epsilon = b.create<arith::ConstantOp>(
loc, b.getFloatAttr(b.getF64Type(), 5.4210108E-20));
Value range = b.create<arith::SubFOp>(loc, max, min);
Value scale = b.create<arith::MulFOp>(loc, range, epsilon);
// res = cast(F64, tempN) * scale + min
Value updateFloat = b.create<arith::UIToFPOp>(loc, b.getF64Type(), randomVal);
Value updateScaled = b.create<arith::MulFOp>(loc, updateFloat, scale);
Value uniformSample = b.create<arith::AddFOp>(loc, updateScaled, min);
return uniformSample;
}
namespace {
class ConvertAtenUniformOp : public OpConversionPattern<AtenUniformOp> {
public:
using OpConversionPattern::OpConversionPattern;
LogicalResult
matchAndRewrite(AtenUniformOp op, OpAdaptor adaptor,
ConversionPatternRewriter &rewriter) const override {
if (failed(verifyLinalgCompatibleTypes(op, rewriter)))
return failure();
Location loc = op.getLoc();
Value self = adaptor.getSelf();
Value from = adaptor.getFrom();
Value to = adaptor.getTo();
Value generator = adaptor.getGenerator();
RankedTensorType resultType = cast<RankedTensorType>(self.getType());
Type elemTy = resultType.getElementType();
Type f64Ty = rewriter.getF64Type();
if (!isa<mlir::FloatType>(elemTy))
return rewriter.notifyMatchFailure(op, "This op only support float type");
if (!isa<Torch::NoneType>(generator.getType()))
return rewriter.notifyMatchFailure(
op, "The generator has to be None because only global default "
"generator is supported");
// Get key, min and max used by `linalg.generic` compute payload.
Value key = rewriter.create<TorchConversion::GetNextSeedOp>(loc);
Value min = convertScalarToDtype(rewriter, loc, from, f64Ty);
Value max = convertScalarToDtype(rewriter, loc, to, f64Ty);
// Construct the `linalg.generic` op.
auto resultRank = resultType.getRank();
SmallVector<AffineMap, 1> indexingMaps(
1, rewriter.getMultiDimIdentityMap(resultRank));
SmallVector<utils::IteratorType> iteratorTypes(
resultRank, utils::IteratorType::parallel);
SmallVector<Value> sizes = getTensorSizes(rewriter, loc, self);
SmallVector<Value> sizesIntValues =
castIndexVectorToInt64Vector(rewriter, loc, sizes);
Value initTensor =
rewriter.create<tensor::EmptyOp>(loc, getAsOpFoldResult(sizes), elemTy);
Value uniformRes =
rewriter
.create<linalg::GenericOp>(
loc, initTensor.getType(), /*inputs=*/ValueRange{},
/*outputs=*/initTensor, indexingMaps, iteratorTypes,
[&](OpBuilder &b, Location loc, ValueRange args) {
SmallVector<Value> indicesIntValues;
for (int i = 0; i < resultRank; i++) {
indicesIntValues.push_back(castIndexToInt64(
b, loc, b.create<linalg::IndexOp>(loc, i)));
}
Value linearIndex =
toLinearIndex(b, loc, indicesIntValues, sizesIntValues);
Value res =
randomUniformF64(b, loc, linearIndex, key, min, max);
Value truncRes = res;
if (isa<Float16Type, Float32Type>(elemTy))
truncRes = b.create<arith::TruncFOp>(loc, elemTy, res);
b.create<linalg::YieldOp>(loc, truncRes);
})
.getResult(0);
Type newResultType = getTypeConverter()->convertType(op.getType());
rewriter.replaceOpWithNewOp<tensor::CastOp>(op, newResultType, uniformRes);
return success();
}
};
} // namespace
namespace {
class ConvertAtenMultinomialOp : public OpConversionPattern<AtenMultinomialOp> {
public:
using OpConversionPattern::OpConversionPattern;
LogicalResult
matchAndRewrite(AtenMultinomialOp op, OpAdaptor adaptor,
ConversionPatternRewriter &rewriter) const override {
if (failed(verifyLinalgCompatibleTypes(op, rewriter)))
return failure();
Location loc = op.getLoc();
Value self = adaptor.getSelf();
Value numSamples = adaptor.getNumSamples();
Value generator = adaptor.getGenerator();
RankedTensorType selfType = cast<RankedTensorType>(self.getType());
Type elemTy = selfType.getElementType();
Type f64Ty = rewriter.getF64Type();
Type i64Ty = rewriter.getI64Type();
Type indexTy = rewriter.getIndexType();
int64_t inputRank = selfType.getRank();
bool bReplacement;
if (!isa<mlir::FloatType>(elemTy))
return rewriter.notifyMatchFailure(op, "This op only support float type");
if (!mlir::isa<Torch::NoneType>(generator.getType()))
return rewriter.notifyMatchFailure(
op, "The generator has to be None because only global default "
"generator is supported");
if (!matchPattern(op.getReplacement(), m_TorchConstantBool(&bReplacement)))
return rewriter.notifyMatchFailure(
op, "Unsupported: replacement must be a boolean value");
if (!bReplacement)
return rewriter.notifyMatchFailure(op,
"Unimplemented: replacement = False");
if (!mlir::isa<mlir::IntegerType>(numSamples.getType())) {
return rewriter.notifyMatchFailure(
op, "Unsupported: num_samples must be an integer value");
}
if (!(inputRank == 1 || inputRank == 2)) {
return rewriter.notifyMatchFailure(
op, "torch.multinomial accepts only rank 1 or 2 tensors as weights");
}
Value cstZero = rewriter.create<arith::ConstantOp>(
loc, i64Ty, rewriter.getI64IntegerAttr(0));
Value cstOne = rewriter.create<arith::ConstantOp>(
loc, i64Ty, rewriter.getI64IntegerAttr(1));
Value zeroIndex = rewriter.create<arith::ConstantIndexOp>(loc, 0);
Value oneIndex = rewriter.create<arith::ConstantIndexOp>(loc, 1);
Value numSamplesIndex =
rewriter.create<arith::IndexCastOp>(loc, indexTy, numSamples);
Value numDistributions;
Value numCategoriesIndex;
ValueRange resultShape;
if (inputRank == 1) {
numDistributions = cstOne;
numCategoriesIndex =
rewriter.create<tensor::DimOp>(loc, indexTy, self, zeroIndex);
resultShape = ValueRange{numSamplesIndex};
} else {
Value numDistIndex =
rewriter.create<tensor::DimOp>(loc, indexTy, self, zeroIndex);
numCategoriesIndex =
rewriter.create<tensor::DimOp>(loc, indexTy, self, oneIndex);
numDistributions =
rewriter.create<arith::IndexCastOp>(loc, i64Ty, numDistIndex);
resultShape = ValueRange{numDistIndex, numSamplesIndex};
}
Value numCategories =
rewriter.create<arith::IndexCastOp>(loc, i64Ty, numCategoriesIndex);
Value resultTensor = rewriter.create<tensor::EmptyOp>(
loc, getAsOpFoldResult(resultShape), i64Ty);
// sum weights for normalization
torch_to_linalg::ReductionOpInfo opInfo;
if (inputRank == 1)
opInfo = {false, self, {0}};
else
opInfo = {false, self, {1}};
Value initSum = rewriter.create<arith::ConstantOp>(
loc, f64Ty, rewriter.getF64FloatAttr(0.0));
auto sumBody = [&](OpBuilder &b, Location loc, ValueRange payloadArgs) {
Value input = payloadArgs[0];
Value result = payloadArgs[1];
Value nextSum = b.create<arith::AddFOp>(loc, input, result);
b.create<linalg::YieldOp>(loc, nextSum);
};
Value sumWeights = torch_to_linalg::createReductionLinalgGeneric(
rewriter, loc, opInfo, initSum, sumBody);
// Get multinomial samples for each weight vector
auto multinomialComputation = [&](OpBuilder &b, Location loc, Value j,
ValueRange args) {
Value jIndex = b.create<arith::IndexCastOp>(loc, indexTy, j);
Value sum;
if (inputRank == 1) {
sum = b.create<tensor::ExtractOp>(loc, sumWeights, ValueRange{});
} else {
sum = b.create<tensor::ExtractOp>(loc, sumWeights, ValueRange{jIndex});
}
// compute cdf in loop
Value initCdf = b.create<tensor::EmptyOp>(
loc, getAsOpFoldResult(ValueRange{numCategoriesIndex}), elemTy);
Value cdf =
b.create<scf::ForOp>(
loc, cstZero, numCategories, cstOne, ValueRange{initCdf},
[&](OpBuilder &b, Location loc, Value i, ValueRange vals) {
Value distribution = vals[0];
// if (i > 0)
auto comparisonPredicate = arith::CmpIPredicateAttr::get(
b.getContext(), arith::CmpIPredicate::sgt);
Value condition = b.create<arith::CmpIOp>(
loc, comparisonPredicate, i, cstZero);
Value iIndex = b.create<arith::IndexCastOp>(loc, indexTy, i);
// curr_cum = i > 0 ? prob[i] + prob[i-1] : prob[i]
ValueRange ind;
if (inputRank == 1) {
ind = ValueRange{iIndex};
} else {
ind = ValueRange{jIndex, iIndex};
}
Value currWeight = b.create<tensor::ExtractOp>(loc, self, ind);
Value currMass = b.create<arith::DivFOp>(loc, currWeight, sum);
Value currCum =
b.create<scf::IfOp>(
loc, condition,
[&](OpBuilder &b, Location loc) {
Value prevI =
b.create<arith::SubIOp>(loc, i, cstOne);
Value prevIndex = b.create<arith::IndexCastOp>(
loc, indexTy, prevI);
Value prevMass = b.create<tensor::ExtractOp>(
loc, distribution, ValueRange{prevIndex});
Value currSum = b.create<arith::AddFOp>(
loc, currMass, prevMass);
b.create<scf::YieldOp>(loc, ValueRange(currSum));
},
[&](OpBuilder &b, Location loc) {
b.create<scf::YieldOp>(loc, ValueRange{currMass});
})
.getResult(0);
Value updatedCdf = b.create<tensor::InsertOp>(
loc, currCum, distribution, ValueRange(iIndex));
b.create<scf::YieldOp>(loc, ValueRange(updatedCdf));
})
.getResult(0);
/*
* Above we've computed the CDF for the unnormalized distribution given to
* us by the user. In order to actually sample from this distribution we
* do the following below: 1) Sample a random floating point value, r in
* [0,1), from a uniform distribution. 2) Perform a binary search in the
* cdf to find the first bin in the CDF where cdf[i] < r. This guarantees
* a random sample from the provided distribution with the appropriate
* probabilities.
*
* This logic is pulled straight from PyTorch's Multinomial Kernel:
* https://github.com/pytorch/pytorch/blob/e4623de4cf6097ff399aa9eb0cef44b44ca76da4/aten/src/ATen/native/cpu/MultinomialKernel.cpp#L23
* */
// Get key, min and max used by RNG.
Value key = b.create<TorchConversion::GetNextSeedOp>(loc);
Value min = b.create<arith::ConstantOp>(loc, f64Ty,
rewriter.getF64FloatAttr(0.0));
Value max = b.create<arith::ConstantOp>(loc, f64Ty,
rewriter.getF64FloatAttr(1.0));
// iterate and sample class indices
Value result = args[0];
Value finalResult =
rewriter
.create<scf::ForOp>(
loc, cstZero, numSamples, cstOne, ValueRange{result},
[&](OpBuilder &b, Location loc, Value i, ValueRange args) {
// Sample random float
Value uniformSample =
randomUniformF64(b, loc, i, key, min, max);
// binary search in cdf to find our sample
Value left = b.create<arith::ConstantOp>(
loc, i64Ty, b.getI64IntegerAttr(0));
Value right = numCategories;
auto checkCondition = [&](OpBuilder &b, Location loc,
ValueRange vals) {
Value left = vals[0];
Value right = vals[1];
// while (right > left)
auto comparisonPredicate = arith::CmpIPredicateAttr::get(
b.getContext(), arith::CmpIPredicate::sgt);
Value loopCondition = b.create<arith::CmpIOp>(
loc, comparisonPredicate, right, left);
b.create<scf::ConditionOp>(loc, loopCondition, vals);
};
ValueRange whileResults =
b.create<scf::WhileOp>(
loc, TypeRange{i64Ty, i64Ty},
ValueRange{left, right}, checkCondition,
[&](OpBuilder &b, Location loc, ValueRange vals) {
Value left = vals[0];
Value right = vals[1];
Value two = b.create<arith::ConstantOp>(
loc, i64Ty, b.getI64IntegerAttr(2));
Value diff =
b.create<arith::SubIOp>(loc, right, left);
Value diffMid =
b.create<arith::DivSIOp>(loc, diff, two);
Value midPointer =
b.create<arith::AddIOp>(loc, left, diffMid);
Type indexTy = b.getIndexType();
Value midIndex = b.create<arith::IndexCastOp>(
loc, indexTy, midPointer);
// branch and update search indices
auto thenBlock = [&](OpBuilder &b,
Location loc) {
// left = mid + 1
Value newLeft = b.create<arith::AddIOp>(
loc, midPointer, cstOne);
b.create<scf::YieldOp>(
loc, ValueRange{newLeft, right});
};
auto elseBlock = [&](OpBuilder &b,
Location loc) {
// right = mid
b.create<scf::YieldOp>(
loc, ValueRange{left, midPointer});
};
Value cumProb = b.create<tensor::ExtractOp>(
loc, cdf, ValueRange{midIndex});
auto cmpPredicate =
arith::CmpFPredicateAttr::get(
b.getContext(),
arith::CmpFPredicate::OLT);
Value branchCondition = b.create<arith::CmpFOp>(
loc, cmpPredicate, cumProb, uniformSample);
ValueRange branchResults =
b.create<scf::IfOp>(loc, branchCondition,
thenBlock, elseBlock)
.getResults();
Value newLeft = branchResults[0];
Value newRight = branchResults[1];
b.create<scf::YieldOp>(
loc, ValueRange{newLeft, newRight});
})
.getResults();
// sample_idx = left_pointer
Value samplePointer = whileResults[0];
Value iIndex =
b.create<arith::IndexCastOp>(loc, indexTy, i);
Value prevResult = args[0];
Value newResult;
if (inputRank == 1) {
// result[i] = sample_idx
newResult = b.create<tensor::InsertOp>(
loc, samplePointer, prevResult, ValueRange{iIndex});
} else {
// result[j][i] = sample_idx
newResult = b.create<tensor::InsertOp>(
loc, samplePointer, prevResult,
ValueRange{jIndex, iIndex});
}
b.create<scf::YieldOp>(loc, ValueRange{newResult});
})
.getResult(0);
b.create<scf::YieldOp>(loc, ValueRange{finalResult});
};
Value finalResultTensor =
rewriter
.create<scf::ForOp>(loc, cstZero, numDistributions, cstOne,
ValueRange{resultTensor},
multinomialComputation)
.getResult(0);
Type newResultType = getTypeConverter()->convertType(op.getType());
rewriter.replaceOpWithNewOp<tensor::CastOp>(op, newResultType,
finalResultTensor);
return success();
}
};
} // namespace
void mlir::torch::torch_to_linalg::populateRandomPatternsAndLegality(
TypeConverter &typeConverter, RewritePatternSet &patterns,
ConversionTarget &target) {
MLIRContext *context = patterns.getContext();
target.addIllegalOp<AtenDropoutOp>();
patterns.add<ConvertAtenDropoutOp>(typeConverter, context);
target.addIllegalOp<AtenUniformOp>();
patterns.add<ConvertAtenUniformOp>(typeConverter, context);
target.addIllegalOp<AtenMultinomialOp>();
patterns.add<ConvertAtenMultinomialOp>(typeConverter, context);
}
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