github.com/gopherd/gonum@v0.0.4/lapack/gonum/dgesv.go (about)

     1  // Copyright ©2021 The Gonum Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package gonum
     6  
     7  import "github.com/gopherd/gonum/blas"
     8  
     9  // Dgesv computes the solution to a real system of linear equations
    10  //  A * X = B
    11  // where A is an n×n matrix and X and B are n×nrhs matrices.
    12  //
    13  // The LU decomposition with partial pivoting and row interchanges is used to
    14  // factor A as
    15  //  A = P * L * U
    16  // where P is a permutation matrix, L is unit lower triangular, and U is upper
    17  // triangular. On return, the factors L and U are stored in a; the unit diagonal
    18  // elements of L are not stored. The row pivot indices that define the
    19  // permutation matrix P are stored in ipiv.
    20  //
    21  // The factored form of A is then used to solve the system of equations A * X =
    22  // B. On entry, b contains the right hand side matrix B. On return, if ok is
    23  // true, b contains the solution matrix X.
    24  func (impl Implementation) Dgesv(n, nrhs int, a []float64, lda int, ipiv []int, b []float64, ldb int) (ok bool) {
    25  	switch {
    26  	case n < 0:
    27  		panic(nLT0)
    28  	case nrhs < 0:
    29  		panic(nrhsLT0)
    30  	case lda < max(1, n):
    31  		panic(badLdA)
    32  	case ldb < max(1, nrhs):
    33  		panic(badLdB)
    34  	}
    35  
    36  	// Quick return if possible.
    37  	if n == 0 || nrhs == 0 {
    38  		return true
    39  	}
    40  
    41  	switch {
    42  	case len(a) < (n-1)*lda+n:
    43  		panic(shortAB)
    44  	case len(ipiv) != n:
    45  		panic(badLenIpiv)
    46  	case len(b) < (n-1)*ldb+nrhs:
    47  		panic(shortB)
    48  	}
    49  
    50  	ok = impl.Dgetrf(n, n, a, lda, ipiv)
    51  	if ok {
    52  		impl.Dgetrs(blas.NoTrans, n, nrhs, a, lda, ipiv, b, ldb)
    53  	}
    54  
    55  	return ok
    56  }