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Make osme things constexpr

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This commit is contained in:
Chris Robinson 2020-08-10 15:11:52 -07:00
parent e8b3e82f96
commit c549797af0
1 changed files with 15 additions and 17 deletions
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32
common/polyphase_resampler.cpp
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@ -10,7 +10,7 @@
namespace { namespace {
#define EPSILON 1e-9 constexpr double Epsilon{1e-9};
using uint = unsigned int; using uint = unsigned int;
@ -21,7 +21,7 @@ using uint = unsigned int;
*/ */
double Sinc(const double x) double Sinc(const double x)
{ {
if UNLIKELY(std::abs(x) < EPSILON) if UNLIKELY(std::abs(x) < Epsilon)
return 1.0; return 1.0;
return std::sin(al::MathDefs<double>::Pi()*x) / (al::MathDefs<double>::Pi()*x); return std::sin(al::MathDefs<double>::Pi()*x) / (al::MathDefs<double>::Pi()*x);
} }
@ -32,22 +32,20 @@ double Sinc(const double x)
* I_0(x) = sum_{k=0}^inf (1 / k!)^2 (x / 2)^(2 k) * I_0(x) = sum_{k=0}^inf (1 / k!)^2 (x / 2)^(2 k)
* = sum_{k=0}^inf ((x / 2)^k / k!)^2 * = sum_{k=0}^inf ((x / 2)^k / k!)^2
*/ */
double BesselI_0(const double x) constexpr double BesselI_0(const double x)
{ {
double term, sum, x2, y, last_sum;
int k;
// Start at k=1 since k=0 is trivial. // Start at k=1 since k=0 is trivial.
term = 1.0; const double x2{x/2.0};
sum = 1.0; double term{1.0};
x2 = x/2.0; double sum{1.0};
k = 1; int k{1};
// Let the integration converge until the term of the sum is no longer // Let the integration converge until the term of the sum is no longer
// significant. // significant.
double last_sum{};
do { do {
y = x2 / k; const double y{x2 / k};
k++; ++k;
last_sum = sum; last_sum = sum;
term *= y * y; term *= y * y;
sum += term; sum += term;
@ -77,11 +75,11 @@ double Kaiser(const double b, const double k)
} }
// Calculates the greatest common divisor of a and b. // Calculates the greatest common divisor of a and b.
uint Gcd(uint x, uint y) constexpr uint Gcd(uint x, uint y)
{ {
while(y > 0) while(y > 0)
{ {
uint z{y}; const uint z{y};
y = x % y; y = x % y;
x = z; x = z;
} }
@ -95,16 +93,16 @@ uint Gcd(uint x, uint y)
* { ceil(5.79 / 2 pi f_t), r <= 21. * { ceil(5.79 / 2 pi f_t), r <= 21.
* *
*/ */
uint CalcKaiserOrder(const double rejection, const double transition) constexpr uint CalcKaiserOrder(const double rejection, const double transition)
{ {
double w_t = 2.0 * al::MathDefs<double>::Pi() * transition; const double w_t{2.0 * al::MathDefs<double>::Pi() * transition};
if LIKELY(rejection > 21.0) if LIKELY(rejection > 21.0)
return static_cast<uint>(std::ceil((rejection - 7.95) / (2.285 * w_t))); return static_cast<uint>(std::ceil((rejection - 7.95) / (2.285 * w_t)));
return static_cast<uint>(std::ceil(5.79 / w_t)); return static_cast<uint>(std::ceil(5.79 / w_t));
} }
// Calculates the beta value of the Kaiser window. Rejection is in dB. // Calculates the beta value of the Kaiser window. Rejection is in dB.
double CalcKaiserBeta(const double rejection) constexpr double CalcKaiserBeta(const double rejection)
{ {
if LIKELY(rejection > 50.0) if LIKELY(rejection > 50.0)
return 0.1102 * (rejection - 8.7); return 0.1102 * (rejection - 8.7);