// Mul computes the product of two matrices a,b and puts
// it in receiver.
// a = mxk, b = kxn, c = mxn
func (c *mesh) Mul(s float64, a, b Mesher) {
m, k := a.Size()
br, n := b.Size()
var (
icoff, iaoff, lboff int
ctmp []float64
tmp float64
)
if k != br {
panic("mesh: Mul: Columns of 'a' != Rows of 'b'")
}
aoff, boff, coff := k, n, n
for i := 0; i < m; i++ {
icoff = i * coff
iaoff = i * aoff
ctmp = c.elems[icoff : icoff+n]
for l, v := range a.(*mesh).elems[iaoff : iaoff+k] {
lboff = l * boff
tmp = s * v
if tmp != 0 {
amd.DaxpyUnitary(tmp, b.(*mesh).elems[lboff:lboff+n], ctmp, ctmp)
}
}
}
}
// Sum computes the sum of meshes, m & n and puts
// result in receiver.
// m, n and o should have same dimensions.
// a*m + n = o
// we will calculate the sum of meshes using
// a slight variation of saxpy
// ie ax+by, x and y are vectors and
// a, b are scalars.
func (o *mesh) Sum(a, b float64, m, n Mesher) {
// the size of all the meshes are assumed to be
// equal and no check is performed, we want this
// to be as fast an operation as possible
_, mc := m.Size() // no. of cols of the meshes
mv := make([]float64, mc) // col vector of m
nv := make([]float64, mc) // col vector of n
ov := make([]float64, mc) // col vector of o
// we will scale the meshes
if a == 0 && b == 1 {
// z = 0*x + y
// we just copy n into o
o.Clone(n)
return
}
if b == 0 && a == 1 {
// z = x + 0*y
// we just copy m into o
o.Clone(m)
return
}
if a == 1 && b != 1 {
// z = x + by
// we scale n
ns := n.Slice()
for j := range ns {
ns[j] *= b
}
} else if a != 1 && b == 1 {
// z = ax + y
// we scale m
ms := m.Slice()
for j := range ms {
ms[j] *= a
}
} else if a == 0 && b == 0 {
o.Zero()
return
}
// we add the meshes by cols
for j := 0; j < mc; j++ {
m.GetCol(mv, j)
n.GetCol(nv, j)
amd.DaxpyUnitary(a, mv, nv, ov)
o.SetCol(ov, j)
}
}
// Sum computes the sum of two vectors
func Sum(s float64, a, b, c []float64) {
amd.DaxpyUnitary(s, a, b, c)
}
