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dense.go
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dense.go
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package matrix
import (
"fmt"
)
type Dense struct {
v []float64 // [row, row, ..., row]
numrow int
numcol int
stride int // The distance between vertically adjacent elements.
}
// AsDense makes new dense matrix that refers to v
func AsDense(numrow, numcol int, v []float64) Dense {
n := numrow * numcol
if n > len(v) {
panic("matrix: AsDense: numrow*numcol > len(v)")
}
return Dense{v: v[:n], numrow: numrow, numcol: numcol, stride: numcol}
}
// MakeDense allocates new dense matrix and initializes its first elements to
// values specified by iv.
func MakeDense(numrow, numcol int, iv ...float64) Dense {
v := make([]float64, numrow*numcol)
copy(v, iv)
return AsDense(numrow, numcol, v)
}
// IsValid reports whether d represents valid matrix value.
func (d Dense) IsValid() bool {
return len(d.v) > 0 && d.numrow > 0 && d.numcol > 0 && d.stride > 0
}
// SetAll sets all elements of d to a.
func (d Dense) SetAll(a float64) {
for i := 0; i < d.numrow; i++ {
row := d.v[i*d.stride:]
k := d.numcol - 1
for k > 0 {
row[k] = a
row[k-1] = a
k -= 2
}
if k == 0 {
row[0] = a
}
}
}
// SetI sets elements of d to create identity matrix (panics if d is not square).
func (d Dense) SetIdentity() {
if d.numrow != d.numcol {
panic("matrix: SetI on non square matrix")
}
d.SetAll(0)
for i := 0; i < len(d.v); i += d.stride + 1 {
d.v[i] = 1
}
}
// Size returns dimensions of the matrix (rows, cols).
func (d Dense) Size() (int, int) {
return d.numrow, d.numcol
}
// NumRow returns number of rows.
func (d Dense) NumRow() int {
return d.numrow
}
// NumCol returns number of columns.
func (d Dense) NumCol() int {
return d.numcol
}
// Stride returns distance between vertically adjacent elements.
func (d Dense) Stride() int {
return d.stride
}
// Elems returns internal buffer of elements. Be careful when use returned slice.
// For example you can not assume that its length corresponds to dimensions of d.
func (d Dense) Elems() []float64 {
return d.v
}
// Get returns element from row i, column k.
func (d Dense) Get(i, k int) float64 {
return d.v[i*d.stride+k]
}
// Set sets element in row i and column k.
func (d Dense) Set(i, k int, a float64) {
d.v[i*d.stride+k] = a
}
// Rows returns a slice of a matrix that contains rows from start to stop-1.
func (d Dense) Rows(start, stop int) Dense {
if start > stop || start < 0 || stop > d.numrow {
panic("matrix: bad indexes for horizontal slice")
}
return Dense{
v: d.v[start*d.stride : stop*d.stride],
numrow: stop - start,
numcol: d.numcol,
stride: d.stride,
}
}
// Cols returns a slice of a matrix that contains columns from start to stop-1.
func (d Dense) Cols(start, stop int) Dense {
if start > stop || start < 0 || stop > d.numcol {
panic("matrix: bad indexes for vertical slice")
}
return Dense{
v: d.v[start : (d.numrow-1)*d.stride+stop],
numrow: d.numrow,
numcol: stop - start,
stride: d.stride,
}
}
// AsRow returns horizontal vector that refers to d. Panics if cols != stride.
func (d Dense) AsRow() Dense {
if d.numcol != d.stride {
panic("matrix: AsRow: numcol != stride")
}
return Dense{v: d.v, numrow: 1, numcol: len(d.v), stride: len(d.v)}
}
// AsCol returns vertical vector that refers to d. Panics if numcol != stride.
func (d Dense) AsCol() Dense {
if d.numcol != d.stride {
panic("matrix: AsCol: numcol != stride")
}
return Dense{v: d.v, numrow: len(d.v), numcol: 1, stride: 1}
}
// Equal returns true if matrices are equal
func (d Dense) Equal(a Dense) bool {
if d.numrow != a.numrow || d.numcol != a.numcol {
return false
}
for i := 0; i < d.numrow; i++ {
dr := d.v[i*d.stride:]
ar := a.v[i*a.stride:]
for k := 0; k < d.numcol; k++ {
if dr[k] != ar[k] {
return false
}
}
}
return true
}
func (d Dense) Format(f fmt.State, c rune) {
format := "%g"
switch c {
case 'f':
format = "%f"
case 'e':
format = "%e"
case 'G':
format = "%G"
case 'E':
format = "%E"
case 'F':
format = "%F"
}
lastrow, lastcol := d.Size()
lastrow--
lastcol--
f.Write([]byte{'{'})
for i := 0; i <= lastrow; i++ {
if i > 0 {
f.Write([]byte{'\n'})
}
for k := 0; k <= lastcol; k++ {
fmt.Fprintf(f, format, d.Get(i, k))
if k < lastcol {
f.Write([]byte{','})
}
}
if i < lastrow {
f.Write([]byte{','})
}
}
f.Write([]byte{'}'})
}
// Utils
func (d Dense) checkDim(a Dense) {
if d.numrow != a.numrow || d.numcol != a.numcol {
panic("matrix: dimensions not equal")
}
}