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[bytom/vapor.git] / vendor / gonum.org / v1 / gonum / lapack / gonum / dgelqf.go

diff --git a/vendor/gonum.org/v1/gonum/lapack/gonum/dgelqf.go b/vendor/gonum.org/v1/gonum/lapack/gonum/dgelqf.go
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+++ b/vendor/gonum.org/v1/gonum/lapack/gonum/dgelqf.go
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+// Copyright ©2015 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
+
+import (
+       "gonum.org/v1/gonum/blas"
+       "gonum.org/v1/gonum/lapack"
+)
+
+// Dgelqf computes the LQ factorization of the m×n matrix A using a blocked
+// algorithm. See the documentation for Dgelq2 for a description of the
+// parameters at entry and exit.
+//
+// work is temporary storage, and lwork specifies the usable memory length.
+// At minimum, lwork >= m, and this function will panic otherwise.
+// Dgelqf is a blocked LQ factorization, but the block size is limited
+// by the temporary space available. If lwork == -1, instead of performing Dgelqf,
+// the optimal work length will be stored into work[0].
+//
+// tau must have length at least min(m,n), and this function will panic otherwise.
+func (impl Implementation) Dgelqf(m, n int, a []float64, lda int, tau, work []float64, lwork int) {
+       nb := impl.Ilaenv(1, "DGELQF", " ", m, n, -1, -1)
+       lworkopt := m * max(nb, 1)
+       if lwork == -1 {
+               work[0] = float64(lworkopt)
+               return
+       }
+       checkMatrix(m, n, a, lda)
+       if len(work) < lwork {
+               panic(shortWork)
+       }
+       if lwork < m {
+               panic(badWork)
+       }
+       k := min(m, n)
+       if len(tau) < k {
+               panic(badTau)
+       }
+       if k == 0 {
+               return
+       }
+       // Find the optimal blocking size based on the size of available memory
+       // and optimal machine parameters.
+       nbmin := 2
+       var nx int
+       iws := m
+       ldwork := nb
+       if nb > 1 && k > nb {
+               nx = max(0, impl.Ilaenv(3, "DGELQF", " ", m, n, -1, -1))
+               if nx < k {
+                       iws = m * nb
+                       if lwork < iws {
+                               nb = lwork / m
+                               nbmin = max(2, impl.Ilaenv(2, "DGELQF", " ", m, n, -1, -1))
+                       }
+               }
+       }
+       // Computed blocked LQ factorization.
+       var i int
+       if nb >= nbmin && nb < k && nx < k {
+               for i = 0; i < k-nx; i += nb {
+                       ib := min(k-i, nb)
+                       impl.Dgelq2(ib, n-i, a[i*lda+i:], lda, tau[i:], work)
+                       if i+ib < m {
+                               impl.Dlarft(lapack.Forward, lapack.RowWise, n-i, ib,
+                                       a[i*lda+i:], lda,
+                                       tau[i:],
+                                       work, ldwork)
+                               impl.Dlarfb(blas.Right, blas.NoTrans, lapack.Forward, lapack.RowWise,
+                                       m-i-ib, n-i, ib,
+                                       a[i*lda+i:], lda,
+                                       work, ldwork,
+                                       a[(i+ib)*lda+i:], lda,
+                                       work[ib*ldwork:], ldwork)
+                       }
+               }
+       }
+       // Perform unblocked LQ factorization on the remainder.
+       if i < k {
+               impl.Dgelq2(m-i, n-i, a[i*lda+i:], lda, tau[i:], work)
+       }
+}