add matrix_test.go
This commit is contained in:
Josh Deprez
parent
83d6b23f51
commit
cdc1bf25fc
2 changed files with 143 additions and 1 deletions
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@ -5,6 +5,8 @@ import (
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"image"
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)
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var errSingularMatrix = errors.New("matrix is singular")
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// IntMatrix3 implements a 3x3 integer matrix.
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type IntMatrix3 [3][3]int
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@ -138,7 +140,28 @@ func (a RatMatrix3) Inverse() (RatMatrix3, error) {
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adj := a.Adjugate()
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det := a[0][0].Mul(adj[0][0]).Add(a[0][1].Mul(adj[1][0])).Add(a[0][2].Mul(adj[2][0]))
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if det.N == 0 {
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return RatMatrix3{}, errors.New("matrix is singular")
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return RatMatrix3{}, errSingularMatrix
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}
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return adj.Mul(det.Invert()), nil
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}
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// Concat returns the matrix equivalent to applying matrix a and then b.
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func (a RatMatrix3) Concat(b RatMatrix3) RatMatrix3 {
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return RatMatrix3{
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0: [3]Rat{
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a[0][0].Mul(b[0][0]).Add(a[0][1].Mul(b[1][0])).Add(a[0][2].Mul(b[2][0])),
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a[0][0].Mul(b[0][1]).Add(a[0][1].Mul(b[1][1])).Add(a[0][2].Mul(b[2][1])),
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a[0][0].Mul(b[0][2]).Add(a[0][1].Mul(b[1][2])).Add(a[0][2].Mul(b[2][2])),
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},
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1: [3]Rat{
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a[1][0].Mul(b[0][0]).Add(a[1][1].Mul(b[1][0])).Add(a[1][2].Mul(b[2][0])),
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a[1][0].Mul(b[0][1]).Add(a[1][1].Mul(b[1][1])).Add(a[1][2].Mul(b[2][1])),
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a[1][0].Mul(b[0][2]).Add(a[1][1].Mul(b[1][2])).Add(a[1][2].Mul(b[2][2])),
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},
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2: [3]Rat{
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a[2][0].Mul(b[0][0]).Add(a[2][1].Mul(b[1][0])).Add(a[2][2].Mul(b[2][0])),
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a[2][0].Mul(b[0][1]).Add(a[2][1].Mul(b[1][1])).Add(a[2][2].Mul(b[2][1])),
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a[2][0].Mul(b[0][2]).Add(a[2][1].Mul(b[1][2])).Add(a[2][2].Mul(b[2][2])),
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},
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}
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}
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119
geom/matrix_test.go
Normal file
119
geom/matrix_test.go
Normal file
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@ -0,0 +1,119 @@
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package geom
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import (
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"testing"
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"github.com/google/go-cmp/cmp"
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)
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func TestRatMatrix3InverseAndConcat(t *testing.T) {
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identity := RatMatrix3{
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0: [3]Rat{{1, 1}, {0, 1}, {0, 1}},
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1: [3]Rat{{0, 1}, {1, 1}, {0, 1}},
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2: [3]Rat{{0, 1}, {0, 1}, {1, 1}},
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}
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tests := []struct {
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in, want RatMatrix3
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}{
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{ // identity
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in: identity,
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want: identity,
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},
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{ // diagonal
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in: RatMatrix3{
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0: [3]Rat{{3, 1}, {0, 1}, {0, 1}},
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1: [3]Rat{{0, 1}, {1, 2}, {0, 1}},
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2: [3]Rat{{0, 1}, {0, 1}, {7, 13}},
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},
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want: RatMatrix3{
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0: [3]Rat{{1, 3}, {0, 1}, {0, 1}},
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1: [3]Rat{{0, 1}, {2, 1}, {0, 1}},
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2: [3]Rat{{0, 1}, {0, 1}, {13, 7}},
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},
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},
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{ // hexagonal prism layout
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in: RatMatrix3{
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0: [3]Rat{{24, 1}, {0, 1}, {0, 1}},
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1: [3]Rat{{0, 1}, {16, 1}, {0, 1}},
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2: [3]Rat{{8, 1}, {0, 1}, {16, 1}},
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},
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want: RatMatrix3{
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0: [3]Rat{{1, 24}, {0, 1}, {0, 1}},
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1: [3]Rat{{0, 1}, {1, 16}, {0, 1}},
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2: [3]Rat{{-1, 48}, {0, 1}, {1, 16}},
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},
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},
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{ // random small positive integer matrix
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in: RatMatrix3{
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0: [3]Rat{{90, 1}, {40, 1}, {15, 1}},
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1: [3]Rat{{28, 1}, {54, 1}, {77, 1}},
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2: [3]Rat{{35, 1}, {99, 1}, {9, 1}},
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},
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want: RatMatrix3{
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0: [3]Rat{{7137, 531380}, {-225, 106276}, {-227, 53138}},
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1: [3]Rat{{-2443, 531380}, {-57, 106276}, {651, 53138}},
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2: [3]Rat{{-441, 265690}, {751, 53138}, {-187, 26569}},
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},
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},
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{ // random small integer matrix
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in: RatMatrix3{
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0: [3]Rat{{-38, 1}, {-23, 1}, {60, 1}},
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1: [3]Rat{{-75, 1}, {-22, 1}, {33, 1}},
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2: [3]Rat{{-5, 1}, {-6, 1}, {-14, 1}},
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},
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want: RatMatrix3{
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0: [3]Rat{{46, 2647}, {-62, 2647}, {51, 2647}},
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1: [3]Rat{{-1215, 29117}, {832, 29117}, {-3246, 29117}},
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2: [3]Rat{{340, 29117}, {-113, 29117}, {-889, 29117}},
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},
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},
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}
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for _, test := range tests {
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got, err := test.in.Inverse()
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if err != nil {
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t.Errorf("(%v).Inverse() error = %v, want nil", test.in, err)
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}
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if diff := cmp.Diff(got, test.want); diff != "" {
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t.Errorf("(%v).Inverse() diff:\n%s", test.in, diff)
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}
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got2 := test.in.Concat(got)
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if diff := cmp.Diff(got2, identity); diff != "" {
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t.Errorf("(%v).Concat(%v) diff:\n%s", test.in, got2, diff)
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}
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got3 := got.Concat(test.in)
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if diff := cmp.Diff(got3, identity); diff != "" {
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t.Errorf("(%v).Concat(%v) diff\n%s", got, test.in, diff)
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}
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}
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}
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func TestRatMatrix3InvertSingular(t *testing.T) {
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tests := []RatMatrix3{
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{ // zero row and column
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0: [3]Rat{{1, 1}, {0, 1}, {0, 1}},
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1: [3]Rat{{0, 1}, {1, 1}, {0, 1}},
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2: [3]Rat{{0, 1}, {0, 1}, {0, 1}},
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},
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{ // zero row
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0: [3]Rat{{1, 1}, {0, 1}, {0, 1}},
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1: [3]Rat{{0, 1}, {1, 1}, {1, 1}},
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2: [3]Rat{{0, 1}, {0, 1}, {0, 1}},
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},
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{ // zero column
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0: [3]Rat{{1, 1}, {0, 1}, {0, 1}},
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1: [3]Rat{{0, 1}, {1, 1}, {0, 1}},
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2: [3]Rat{{0, 1}, {1, 1}, {0, 1}},
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},
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{ // product of random 3x2 and 2x3 integer matrices
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0: [3]Rat{{-4330, 1}, {1283, 1}, {2717, 1}},
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1: [3]Rat{{1978, 1}, {-10171, 1}, {571, 1}},
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2: [3]Rat{{-4962, 1}, {-3689, 1}, {4089, 1}},
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},
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}
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for _, test := range tests {
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if _, err := test.Inverse(); err != errSingularMatrix {
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t.Errorf("(%v).Inverse() error = %v, want 'matrix is singular'", test, err)
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}
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}
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}
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