41 lines
850 B
Go
41 lines
850 B
Go
// 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
|
|
|
|
// Iladlr scans a matrix for its last non-zero row. Returns -1 if the matrix
|
|
// is all zeros.
|
|
//
|
|
// Iladlr is an internal routine. It is exported for testing purposes.
|
|
func (Implementation) Iladlr(m, n int, a []float64, lda int) int {
|
|
switch {
|
|
case m < 0:
|
|
panic(mLT0)
|
|
case n < 0:
|
|
panic(nLT0)
|
|
case lda < max(1, n):
|
|
panic(badLdA)
|
|
}
|
|
|
|
if n == 0 || m == 0 {
|
|
return -1
|
|
}
|
|
|
|
if len(a) < (m-1)*lda+n {
|
|
panic(shortA)
|
|
}
|
|
|
|
// Check the common case where the corner is non-zero
|
|
if a[(m-1)*lda] != 0 || a[(m-1)*lda+n-1] != 0 {
|
|
return m - 1
|
|
}
|
|
for i := m - 1; i >= 0; i-- {
|
|
for j := 0; j < n; j++ {
|
|
if a[i*lda+j] != 0 {
|
|
return i
|
|
}
|
|
}
|
|
}
|
|
return -1
|
|
}
|