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COMMON: Cos/Sin Table switch internal structure so at() is faster

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A new internal table has been added so that no if checks need to
be performed for the at() lookup.

The old table can still be accessed using getTable or atLegacy().

at() and atLegacy() return the same values, but at() is faster.
This commit is contained in:
David Fioramonti 2018-08-16 16:47:28 -07:00 • committed by Eugene Sandulenko
parent cf99bb0a5e
commit 51c11efbbc
4 changed files with 55 additions and 20 deletions
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24
common/cosinetables.cpp
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@ -34,35 +34,45 @@ CosineTable::CosineTable(int nPoints) {
_nPoints = nPoints;
_radResolution = 2.0 * M_PI / _nPoints;
_refSize = _nPoints / 4;
_table = new float[_nPoints / 2];
_tableEOS = new float[_nPoints / 2];
_table = new float[_nPoints];
for (int i = 0; i < _nPoints; i++)
_table[i] = cos(i * _radResolution);
// Table contains cos(2*pi*i/_nPoints) for 0<=i<=_nPoints/4,
// followed by 3_nPoints/4<=i<_nPoints
for (int i = 0; i <= _nPoints / 4; i++)
_table[i] = cos(i * _radResolution);
_tableEOS[i] = cos(i * _radResolution);
for (int i = 1; i < _nPoints / 4; i++)
_table[_nPoints / 2 - i] = _table[i];
_tableEOS[_nPoints / 2 - i] = _tableEOS[i];
}
float CosineTable::at(int index) const {
assert((index >= 0) && (index < _nPoints));
return _table[index];
}
float CosineTable::atLegacy(int index) const {
assert((index >= 0) && (index < _nPoints));
if (index < _refSize)
// [0,pi/2)
return _table[index];
return _tableEOS[index];
if ((index > _refSize) && (index < 2 * _refSize))
// (pi/2,pi)
return -_table[2 * _refSize - index];
return -_tableEOS[2 * _refSize - index];
if ((index >= 2 * _refSize) && (index < 3 * _refSize))
// [pi,3/2pi)
return -_table[index - 2 * _refSize];
return -_tableEOS[index - 2 * _refSize];
if ((index > 3 * _refSize) && (index < _nPoints))
// (3/2pi,2pi)
return _table[_nPoints - index];
return _tableEOS[_nPoints - index];
return 0.0f; // cos(pi/2) and cos(3pi/2) = 0
}
CosineTable::~CosineTable() {
delete[] _tableEOS;
delete[] _table;
}