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accel: limit how far we will search in findBest

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Justin Viiret 2017-05-17 14:43:15 +10:00 committed by Matthew Barr
parent fb3a03dc69
commit cfdac66404
1 changed files with 33 additions and 8 deletions
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41
src/nfagraph/ng_limex_accel.cpp
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@ -215,16 +215,30 @@ struct SAccelScheme {
}; };
} }
/**
* \brief Limit on the number of (recursive) calls to findBestInternal().
*/
static constexpr size_t MAX_FINDBEST_CALLS = 1000000;
static static
void findBest(vector<vector<CharReach> >::const_iterator pb, void findBestInternal(vector<vector<CharReach>>::const_iterator pb,
vector<vector<CharReach> >::const_iterator pe, vector<vector<CharReach>>::const_iterator pe,
const SAccelScheme &curr, SAccelScheme *best) { size_t *num_calls, const SAccelScheme &curr,
SAccelScheme *best) {
assert(curr.offset <= MAX_ACCEL_DEPTH); assert(curr.offset <= MAX_ACCEL_DEPTH);
if (++(*num_calls) > MAX_FINDBEST_CALLS) {
DEBUG_PRINTF("hit num_calls limit %zu\n", *num_calls);
return;
}
DEBUG_PRINTF("paths left %zu\n", pe - pb); DEBUG_PRINTF("paths left %zu\n", pe - pb);
if (pb == pe) { if (pb == pe) {
if (curr < *best) { if (curr < *best) {
DEBUG_PRINTF("new best\n");
*best = curr; *best = curr;
DEBUG_PRINTF("new best: count=%zu, class=%s, offset=%u\n",
best->cr.count(), describeClass(best->cr).c_str(),
best->offset);
} }
return; return;
} }
@ -262,7 +276,7 @@ void findBest(vector<vector<CharReach> >::const_iterator pb,
DEBUG_PRINTF("worse\n"); DEBUG_PRINTF("worse\n");
continue; continue;
} }
findBest(pb + 1, pe, in, best); findBestInternal(pb + 1, pe, num_calls, in, best);
if (curr.cr == best->cr) { if (curr.cr == best->cr) {
return; /* could only get better by offset */ return; /* could only get better by offset */
@ -270,6 +284,19 @@ void findBest(vector<vector<CharReach> >::const_iterator pb,
} }
} }
static
SAccelScheme findBest(const vector<vector<CharReach>> &paths,
const CharReach &terminating) {
SAccelScheme curr(terminating, 0U);
SAccelScheme best;
size_t num_calls = 0;
findBestInternal(paths.begin(), paths.end(), &num_calls, curr, &best);
DEBUG_PRINTF("findBest completed, num_calls=%zu\n", num_calls);
DEBUG_PRINTF("selected scheme: count=%zu, class=%s, offset=%u\n",
best.cr.count(), describeClass(best.cr).c_str(), best.offset);
return best;
}
namespace { namespace {
struct DAccelScheme { struct DAccelScheme {
DAccelScheme(CharReach cr_in, u32 offset_in) DAccelScheme(CharReach cr_in, u32 offset_in)
@ -557,9 +584,7 @@ AccelScheme findBestAccelScheme(vector<vector<CharReach>> paths,
/* if we were smart we would do something netflowy on the paths to find the /* if we were smart we would do something netflowy on the paths to find the
* best cut. But we aren't, so we will just brute force it. * best cut. But we aren't, so we will just brute force it.
*/ */
SAccelScheme curr(terminating, 0U); SAccelScheme best = findBest(paths, terminating);
SAccelScheme best;
findBest(paths.begin(), paths.end(), curr, &best);
/* find best is a bit lazy in terms of minimising the offset, see if we can /* find best is a bit lazy in terms of minimising the offset, see if we can
* make it better. need to find the min max offset that we need.*/ * make it better. need to find the min max offset that we need.*/