func Points(x, y []float64, c *CoefsType) *CoefsType {
// make sure size is right
if c == nil {
c = New()
}
c.setSize(len(x))
// set up to compute coefficients
// h has length n-1
for i := 0; i < (c.n - 1); i++ {
c.h[i] = x[i+1] - x[i]
}
// diagonal of size n-2
for i := 0; i < (c.n - 2); i++ {
c.b[i] = 2.0 * (c.h[i] + c.h[i+1])
}
// rhs of size n-2
for i := 1; i < (c.n - 1); i++ {
c.d[i-1] = 6.0 * (((y[i+1] - y[i]) / c.h[i]) - ((y[i] - y[i-1]) / c.h[i-1]))
}
// set second derivatives for natural spline
c.S[0] = 0.0
c.S[c.n-1] = 0.0
fmt.Printf("calling solver\n")
//util.DumpSlice("h",c.h)
// call tridiagonal solver
solver.Tdma(c.h[:], // lower diagonal
c.b[:], // diagonal
c.h[1:], // upper diagonal
c.d[:], // rhs
c.S[1:], // unkknown
c.cp, // work_a
c.dp) // work_b
// save the coefficients
for i := 0; i < (c.n - 1); i++ {
c.coef_a[i] = (c.S[i+1] - c.S[i]) / (6.0 * c.h[i])
c.coef_b[i] = c.S[i] / 2.0
c.coef_c[i] = ((y[i+1] - y[i]) / c.h[i]) - ((2.0*c.h[i]*c.S[i] + c.h[i]*c.S[i+1]) / 6.0)
c.coef_d[i] = y[i]
}
//util.DumpSlice("coef_a",c.coef_a)
//util.DumpSlice("coef_b",c.coef_b)
//util.DumpSlice("coef_c",c.coef_c)
//util.DumpSlice("coef_d",c.coef_d)
return c
}
func TestSolver(n int) {
fmt.Printf("Testing TDMA Solver\n")
now := time.Now()
seed := now.Unix()
rand.Seed(seed)
A := algebra.NewMat(n, n)
x := make([]float64, n)
b := make([]float64, n)
for i := 0; i < n; i++ {
x[i] = rand.Float64()
A[i][i] = rand.Float64()
if i < (n - 1) {
A[i+1][i] = rand.Float64()
A[i][i+1] = rand.Float64()
}
}
algebra.MatMul(A, x, b)
algebra.MatInfo(A)
util.DumpSlice("x", x)
util.DumpSlice("b", b)
diag := make([]float64, n)
unk := make([]float64, n)
od_l := make([]float64, n)
od_u := make([]float64, n)
for i := 0; i < n; i++ {
diag[i] = A[i][i]
if i > 0 {
od_l[i] = A[i][i-1]
}
if i < (n - 1) {
od_u[i] = A[i][i+1]
}
}
cp := make([]float64, n)
dp := make([]float64, n)
//util.DumpSlice("diag",diag)
//util.DumpSlice("od_lower",od_l)
//util.DumpSlice("od_upper",od_u)
solver.Tdma(od_l, diag, od_u, b, unk, cp, dp)
util.DumpSlice("result", unk)
}