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// Copyright ©2023 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gonum
// Dptsv computes the solution to system of linear equations
//
// A * X = B
//
// where A is an n×n symmetric positive definite tridiagonal matrix, and X and B
// are n×nrhs matrices. A is factored as A = L*D*Lᵀ, and the factored form of A
// is then used to solve the system of equations.
//
// On entry, d contains the n diagonal elements of A and e contains the (n-1)
// subdiagonal elements of A. On return, d contains the n diagonal elements of
// the diagonal matrix D from the factorization A = L*D*Lᵀ and e contains the
// (n-1) subdiagonal elements of the unit bidiagonal factor L.
//
// Dptsv returns whether the solution X has been successfully computed.
func (impl Implementation) Dptsv(n, nrhs int, d, e []float64, b []float64, ldb int) (ok bool) {
switch {
case n < 0:
panic(nLT0)
case nrhs < 0:
panic(nrhsLT0)
case ldb < max(1, nrhs):
panic(badLdB)
}
if n == 0 || nrhs == 0 {
return true
}
switch {
case len(d) < n:
panic(shortD)
case len(e) < n-1:
panic(shortE)
case len(b) < (n-1)*ldb+nrhs:
panic(shortB)
}
ok = impl.Dpttrf(n, d, e)
if ok {
impl.Dpttrs(n, nrhs, d, e, b, ldb)
}
return ok
}
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