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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
View file

@ -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;
}

12
common/cosinetables.h
View file

@ -46,15 +46,23 @@ public:
* - Entries (excluding) nPoints/4 up to nPoints/2:
* (excluding) cos(3/2*pi) till (excluding) cos(2*pi)
*/
const float *getTable() { return _table; }
const float *getTable() { return _tableEOS; }
/**
* Returns cos(2*pi * index / nPoints )
* Index must be in range [0, nPoints - 1]
* Faster than atLegacy
*/
float at(int index) const;
/**
* Returns cos(2*pi * index / nPoints )
* Index must be in range [0, nPoints - 1]
*/
float at(int index) const;
float atLegacy(int index) const;
private:
float *_tableEOS;
float *_table;
double _radResolution; // Smallest radian increment
int _refSize; // _nPoints / 4

27
common/sinetables.cpp
View file

@ -34,39 +34,48 @@ SineTable::SineTable(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] = sin(i * _radResolution);
// Table contains sin(2*pi*i/_nPoints) for 0<=i<_nPoints/4,
// followed by _nPoints/2<=i<3_nPoints/4
for (int i = 0; i < _nPoints / 4; i++)
_table[i] = sin(i * _radResolution);
_tableEOS[i] = sin(i * _radResolution);
for (int i = 0; i < _nPoints / 4; i++)
_table[_nPoints / 4 + i] = -_table[i];
_tableEOS[_nPoints / 4 + i] = -_tableEOS[i];
}
float SineTable::at(int index) const {
float SineTable::at(int index) const {
assert((index >= 0) && (index < _nPoints));
return _table[index];
}
float SineTable::atLegacy(int index) const {
assert((index >= 0) && (index < _nPoints));
if (index < _refSize)
// [0,pi/2)
return _table[index];
return _tableEOS[index];
if (index == _refSize)
// pi/2
return 1.0f; // sin(pi/2) = 1.0
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 -1.0f; // sin(3pi/2) = -1.0
}
SineTable::~SineTable() {
delete[] _tableEOS;
delete[] _table;
}

12
common/sinetables.h
View file

@ -46,15 +46,23 @@ public:
* - Entries 2_nPoints/4 up to nPoints/2:
* sin(pi) till (excluding) sin(3/2*pi)
*/
const float *getTable() { return _table; }
const float *getTable() { return _tableEOS; }
/**
* Returns sin(2*pi * index / nPoints )
* Index must be in range [0, nPoints - 1]
* Faster than atLegacy
*/
float at(int index) const;
/**
* Returns sin(2*pi * index / nPoints )
* Index must be in range [0, nPoints - 1]
*/
float at(int index) const;
float atLegacy(int index) const;
private:
float *_tableEOS;
float *_table;
double _radResolution; // Smallest radian increment
int _refSize; // _nPoints / 4