//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
#ifndef BUGPOINT_LIST_REDUCER_H
#define BUGPOINT_LIST_REDUCER_H
+#include "llvm/Support/raw_ostream.h"
#include <vector>
-#include <iostream>
+#include <cstdlib>
+#include <algorithm>
namespace llvm {
enum TestResult {
NoFailure, // No failure of the predicate was detected
KeepSuffix, // The suffix alone satisfies the predicate
- KeepPrefix, // The prefix alone satisfies the predicate
+ KeepPrefix // The prefix alone satisfies the predicate
};
virtual ~ListReducer() {}
//
bool reduceList(std::vector<ElTy> &TheList) {
std::vector<ElTy> empty;
+ std::srand(0x6e5ea738); // Seed the random number generator
switch (doTest(TheList, empty)) {
case KeepPrefix:
if (TheList.size() == 1) // we are done, it's the base case and it fails
case KeepSuffix:
// cannot be reached!
- std::cerr << "bugpoint ListReducer internal error: selected empty set.\n";
+ errs() << "bugpoint ListReducer internal error: selected empty set.\n";
abort();
case NoFailure:
return false; // there is no failure with the full set of passes/funcs!
}
+ // Maximal number of allowed splitting iterations,
+ // before the elements are randomly shuffled.
+ const unsigned MaxIterationsWithoutProgress = 3;
+ bool ShufflingEnabled = true;
+
+Backjump:
unsigned MidTop = TheList.size();
- while (MidTop > 1) {
+ unsigned MaxIterations = MaxIterationsWithoutProgress;
+ unsigned NumOfIterationsWithoutProgress = 0;
+ while (MidTop > 1) { // Binary split reduction loop
// Halt if the user presses ctrl-c.
if (BugpointIsInterrupted) {
- std::cerr << "\n\n*** Reduction Interrupted, cleaning up...\n\n";
+ errs() << "\n\n*** Reduction Interrupted, cleaning up...\n\n";
return true;
}
+
+ // If the loop doesn't make satisfying progress, try shuffling.
+ // The purpose of shuffling is to avoid the heavy tails of the
+ // distribution (improving the speed of convergence).
+ if (ShufflingEnabled &&
+ NumOfIterationsWithoutProgress > MaxIterations) {
+ std::vector<ElTy> ShuffledList(TheList);
+ std::random_shuffle(ShuffledList.begin(), ShuffledList.end());
+ errs() << "\n\n*** Testing shuffled set...\n\n";
+ // Check that random shuffle doesn't loose the bug
+ if (doTest(ShuffledList, empty) == KeepPrefix) {
+ // If the bug is still here, use the shuffled list.
+ TheList.swap(ShuffledList);
+ MidTop = TheList.size();
+ // Must increase the shuffling treshold to avoid the small
+ // probability of inifinite looping without making progress.
+ MaxIterations += 2;
+ errs() << "\n\n*** Shuffling does not hide the bug...\n\n";
+ } else {
+ ShufflingEnabled = false; // Disable shuffling further on
+ errs() << "\n\n*** Shuffling hides the bug...\n\n";
+ }
+ NumOfIterationsWithoutProgress = 0;
+ }
unsigned Mid = MidTop / 2;
std::vector<ElTy> Prefix(TheList.begin(), TheList.begin()+Mid);
// shorten the list to the "kept" elements.
TheList.swap(Suffix);
MidTop = TheList.size();
+ // Reset progress treshold and progress counter
+ MaxIterations = MaxIterationsWithoutProgress;
+ NumOfIterationsWithoutProgress = 0;
break;
case KeepPrefix:
// The predicate still holds, shorten the list to the prefix elements.
TheList.swap(Prefix);
MidTop = TheList.size();
+ // Reset progress treshold and progress counter
+ MaxIterations = MaxIterationsWithoutProgress;
+ NumOfIterationsWithoutProgress = 0;
break;
case NoFailure:
// Otherwise the property doesn't hold. Some of the elements we removed
// must be necessary to maintain the property.
MidTop = Mid;
+ NumOfIterationsWithoutProgress++;
break;
}
}
+ // Probability of backjumping from the trimming loop back to the binary
+ // split reduction loop.
+ const int BackjumpProbability = 10;
+
// Okay, we trimmed as much off the top and the bottom of the list as we
// could. If there is more than two elements in the list, try deleting
// interior elements and testing that.
if (TheList.size() > 2) {
bool Changed = true;
std::vector<ElTy> EmptyList;
- while (Changed) {
+ while (Changed) { // Trimming loop.
Changed = false;
- std::vector<ElTy> TrimmedList;
+
+ // If the binary split reduction loop made an unfortunate sequence of
+ // splits, the trimming loop might be left off with a huge number of
+ // remaining elements (large search space). Backjumping out of that
+ // search space and attempting a different split can significantly
+ // improve the convergence speed.
+ if (std::rand() % 100 < BackjumpProbability)
+ goto Backjump;
+
for (unsigned i = 1; i < TheList.size()-1; ++i) { // Check interior elts
if (BugpointIsInterrupted) {
- std::cerr << "\n\n*** Reduction Interrupted, cleaning up...\n\n";
+ errs() << "\n\n*** Reduction Interrupted, cleaning up...\n\n";
return true;
}
projects / oota-llvm.git / blobdiff