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sigProcLib: Remove trigonometric tables 

Trigonometric sin/cos tables are unused after initialization.
There is no benefit to implementing lookup tables for run-once
operations. Also perform initial calculations in double width
because there is no penalty for doing so.

Change-Id: I45bba5daf8610cbba6af95b92c2142f2256491ff
This commit is contained in:
Tom Tsou 2017-06-16 17:08:40 -07:00 committed by Tom Tsou
parent 87d158cc2d
commit bb0c68ae61
1 changed files with 8 additions and 36 deletions
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44
Transceiver52M/sigProcLib.cpp
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@ -46,14 +46,10 @@ using namespace GSM;
#define CLIP_THRESH 30000.0f
/** Lookup tables for trigonometric approximation */
static float cosTable[TABLESIZE+1]; // add 1 element for wrap around
static float sinTable[TABLESIZE+1];
static float sincTable[TABLESIZE+1];
static float sincTable[TABLESIZE+1]; // add 1 element for wrap around
/** Constants */
static const float M_PI_F = (float)M_PI;
static const float M_2PI_F = (float)(2.0*M_PI);
static const float M_1_2PI_F = 1/M_2PI_F;
/* Precomputed rotation vectors */
static signalVector *GMSKRotation4 = NULL;
@ -182,29 +178,6 @@ static float vectorNorm2(const signalVector &x)
return Energy;
}
/** compute e^(-jx) via lookup table. */
static complex expjLookup(float x)
{
float arg = x*M_1_2PI_F;
while (arg > 1.0F) arg -= 1.0F;
while (arg < 0.0F) arg += 1.0F;
const float argT = arg*((float)TABLESIZE);
const int argI = (int)argT;
const float delta = argT-argI;
const float iDelta = 1.0F-delta;
return complex(iDelta*cosTable[argI] + delta*cosTable[argI+1],
iDelta*sinTable[argI] + delta*sinTable[argI+1]);
}
/** Library setup functions */
static void initTrigTables() {
for (int i = 0; i < TABLESIZE+1; i++) {
cosTable[i] = cos(2.0*M_PI*i/TABLESIZE);
sinTable[i] = sin(2.0*M_PI*i/TABLESIZE);
}
}
/*
* Initialize 4 sps and 1 sps rotation tables
*/
@ -216,11 +189,11 @@ static void initGMSKRotationTables()
GMSKReverseRotation4 = new signalVector(len4);
signalVector::iterator rotPtr = GMSKRotation4->begin();
signalVector::iterator revPtr = GMSKReverseRotation4->begin();
float phase = 0.0;
auto phase = 0.0;
while (rotPtr != GMSKRotation4->end()) {
*rotPtr++ = expjLookup(phase);
*revPtr++ = expjLookup(-phase);
phase += M_PI_F / 2.0F / 4.0;
*rotPtr++ = complex(cos(phase), sin(phase));
*revPtr++ = complex(cos(-phase), sin(-phase));
phase += M_PI / 2.0 / 4.0;
}
GMSKRotation1 = new signalVector(len1);
@ -229,9 +202,9 @@ static void initGMSKRotationTables()
revPtr = GMSKReverseRotation1->begin();
phase = 0.0;
while (rotPtr != GMSKRotation1->end()) {
*rotPtr++ = expjLookup(phase);
*revPtr++ = expjLookup(-phase);
phase += M_PI_F / 2.0F;
*rotPtr++ = complex(cos(phase), sin(phase));
*revPtr++ = complex(cos(-phase), sin(-phase));
phase += M_PI / 2.0;
}
}
@ -1887,7 +1860,6 @@ SoftVector *demodAnyBurst(const signalVector &burst, int sps, complex amp,
bool sigProcLibSetup()
{
initTrigTables();
generateSincTable();
initGMSKRotationTables();