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planner: remove Bühlmann factor cache

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The Bühlmann factors were cached in a thread-safe hashmap. It seemed
somewhat dubious that entering a critical section and doing a hash-lookup
would be significantly faster than a simple exp() call.

Indeed, in a very cache friendly test (16 entries, tight loop) calling the
factor() function 32 000 000 times from a different translation units we get:
  - with cache: 604 ms
  - without cache: 266 ms
Therefore, remove the cache. Given that 32 000 000 calls take only 266 ms,
it appears not sensible to try to optimize this function anyway.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
This commit is contained in:
Berthold Stoeger 2020-05-05 22:24:50 +02:00 • committed by Robert C. Helling
parent f37f428762
commit 123937901f
3 changed files with 6 additions and 47 deletions
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25
core/qthelper.cpp
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@ -1601,31 +1601,6 @@ char *intdup(int index)
return strdup(tmpbuf);
}
QHash<int, double> factor_cache;
QReadWriteLock factorCacheLock;
extern "C" double cache_value(int tissue, int timestep, enum inertgas inertgas)
{
double value;
int key = (timestep << 5) + (tissue << 1);
if (inertgas == HE)
++key;
factorCacheLock.lockForRead();
value = factor_cache.value(key);
factorCacheLock.unlock();
return value;
}
extern "C" void cache_insert(int tissue, int timestep, enum inertgas inertgas, double value)
{
int key = (timestep << 5) + (tissue << 1);
if (inertgas == HE)
++key;
factorCacheLock.lockForWrite();
factor_cache.insert(key, value);
factorCacheLock.unlock();
}
extern "C" void print_qt_versions()
{
printf("%s\n", qPrintable(QStringLiteral("built with Qt Version %1, runtime from Qt Version %2").arg(QT_VERSION_STR).arg(qVersion())));