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simplified and made arrays one element shorter

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This commit is contained in:
Ahmet Inan 2018-03-29 08:26:35 +02:00
commit d3cdb23fb2
1 changed files with 13 additions and 14 deletions
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27
spline.hh
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@ -12,28 +12,27 @@ namespace DSP {
template <int KNOTS, typename OTYPE, typename ITYPE>
class UniformNaturalCubicSpline
{
OTYPE A[KNOTS], B[KNOTS], C[KNOTS], D[KNOTS];
OTYPE A[KNOTS-1], B[KNOTS-1], C[KNOTS-1], D[KNOTS-1];
ITYPE x0, dx;
public:
UniformNaturalCubicSpline(OTYPE *y, ITYPE x0 = 0, ITYPE dx = 1, int STRIDE = 1) : x0(x0), dx(dx)
{
for (int i = 0; i < KNOTS; ++i)
A[i] = y[i * STRIDE];
ITYPE u[KNOTS], l[KNOTS];
ITYPE u[KNOTS-1];
u[0] = 0;
l[0] = l[KNOTS-1] = 1;
OTYPE z[KNOTS];
z[0] = z[KNOTS-1] = 0;
OTYPE z[KNOTS-1];
z[0] = 0;
for (int i = 1; i < KNOTS - 1; ++i) {
l[i] = ITYPE(4) - u[i-1];
u[i] = ITYPE(1) / l[i];
z[i] = (ITYPE(3) * (A[i+1] - ITYPE(2) * A[i] + A[i-1]) - z[i-1]) / l[i];
ITYPE l = ITYPE(4) - u[i-1];
u[i] = ITYPE(1) / l;
z[i] = (ITYPE(3) * (y[(i+1)*STRIDE] - ITYPE(2) * y[i*STRIDE] + y[(i-1)*STRIDE]) - z[i-1]) / l;
}
C[KNOTS-1] = 0;
OTYPE c = 0;
for (int i = KNOTS - 2; i >= 0; --i) {
C[i] = z[i] - u[i] * C[i+1];
B[i] = A[i+1] - A[i] - (C[i+1] + ITYPE(2) * C[i]) / ITYPE(3);
D[i] = (C[i+1] - C[i]) / ITYPE(3);
A[i] = y[i * STRIDE];
C[i] = z[i] - u[i] * c;
B[i] = y[(i+1)*STRIDE] - y[i*STRIDE] - (c + ITYPE(2) * C[i]) / ITYPE(3);
D[i] = (c - C[i]) / ITYPE(3);
c = C[i];
}
}
OTYPE operator () (ITYPE x)