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more tests for division

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This commit is contained in:
Roland Averkamp 2015-09-03 13:19:16 +02:00
parent 49e27aea3d
commit 5a16ac0c8f
1 changed files with 55 additions and 17 deletions
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72
decimal_test.go
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@ -715,32 +715,35 @@ func TestDecimal_QuoRem(t *testing.T) {
for _, inp4 := range cases { for _, inp4 := range cases {
d, _ := NewFromString(inp4.d) d, _ := NewFromString(inp4.d)
d2, _ := NewFromString(inp4.d2) d2, _ := NewFromString(inp4.d2)
exp := inp4.exp prec := inp4.exp
q, r := d.QuoRem(d2, exp) q, r := d.QuoRem(d2, prec)
expectedQ, _ := NewFromString(inp4.q) expectedQ, _ := NewFromString(inp4.q)
expectedR, _ := NewFromString(inp4.r) expectedR, _ := NewFromString(inp4.r)
if !q.Equals(expectedQ) || !r.Equals(expectedR) { if !q.Equals(expectedQ) || !r.Equals(expectedR) {
t.Errorf("bad QuoRem division %s , %s , %d got %v, %v expected %s , %s", t.Errorf("bad QuoRem division %s , %s , %d got %v, %v expected %s , %s",
inp4.d, inp4.d2, exp, q, r, inp4.q, inp4.r) inp4.d, inp4.d2, prec, q, r, inp4.q, inp4.r)
} }
if !d.Equals(d2.Mul(q).Add(r)) { if !d.Equals(d2.Mul(q).Add(r)) {
t.Errorf("not fitting") t.Errorf("not fitting: d=%v, d2= %v, prec=%d, q=%v, r=%v",
d, d2, prec, q, r)
} }
if !q.Equals(q.Truncate(exp)) { if !q.Equals(q.Truncate(prec)) {
t.Errorf("quotient wrong precision") t.Errorf("quotient wrong precision: d=%v, d2= %v, prec=%d, q=%v, r=%v",
d, d2, prec, q, r)
} }
if r.Abs().Cmp(d2.Abs().Mul(New(1, -exp))) >= 0 { if r.Abs().Cmp(d2.Abs().Mul(New(1, -prec))) >= 0 {
t.Errorf("remainder too large") t.Errorf("remainder too large: d=%v, d2= %v, prec=%d, q=%v, r=%v",
d, d2, prec, q, r)
} }
if r.value.Sign()*d.value.Sign() < 0 { if r.value.Sign()*d.value.Sign() < 0 {
t.Errorf("signum of divisor and rest do not match") t.Errorf("signum of divisor and rest do not match: d=%v, d2= %v, prec=%d, q=%v, r=%v",
d, d2, prec, q, r)
} }
} }
} }
func TestDecimal_QuoRem2(t *testing.T) { func TestDecimal_QuoRem2(t *testing.T) {
var n int32 = 5 var n int32 = 5
a := []int{1, 2, 3, 6, 7, 10, 100, 14, 5, 400, 0} a := []int{1, 2, 3, 6, 7, 10, 100, 14, 5, 400, 0}
for s := -1; s < 2; s = s + 2 { for s := -1; s < 2; s = s + 2 {
for s2 := -1; s2 < 2; s2 = s2 + 2 { for s2 := -1; s2 < 2; s2 = s2 + 2 {
@ -758,17 +761,26 @@ func TestDecimal_QuoRem2(t *testing.T) {
d := sign1.Mul(New(int64(v1), int32(e1))) d := sign1.Mul(New(int64(v1), int32(e1)))
d2 := sign2.Mul(New(int64(v2), int32(e2))) d2 := sign2.Mul(New(int64(v2), int32(e2)))
q, r := d.QuoRem(d2, prec) q, r := d.QuoRem(d2, prec)
// rule 1: d = d2*q +r
if !d.Equals(d2.Mul(q).Add(r)) { if !d.Equals(d2.Mul(q).Add(r)) {
t.Errorf("not fitting") t.Errorf("not fitting, d=%v, d2=%v, prec=%d, q=%v, r=%v",
d, d2, prec, q, r)
} }
// rule 2: q is integral multiple of 10^(-prec)
if !q.Equals(q.Truncate(prec)) { if !q.Equals(q.Truncate(prec)) {
t.Errorf("quotient wrong precision") t.Errorf("quotient wrong precision, d=%v, d2=%v, prec=%d, q=%v, r=%v",
d, d2, prec, q, r)
} }
// rule 3: abs(r)<abs(d) * 10^(-prec)
if r.Abs().Cmp(d2.Abs().Mul(New(1, -prec))) >= 0 { if r.Abs().Cmp(d2.Abs().Mul(New(1, -prec))) >= 0 {
t.Errorf("remainder too large") t.Errorf("remainder too large, d=%v, d2=%v, prec=%d, q=%v, r=%v",
d, d2, prec, q, r)
} }
// rule 4: r and d have the same sign
if r.value.Sign()*d.value.Sign() < 0 { if r.value.Sign()*d.value.Sign() < 0 {
t.Errorf("signum of divisor and rest do not match") t.Errorf("signum of divisor and rest do not match, "+
"d=%v, d2=%v, prec=%d, q=%v, r=%v",
d, d2, prec, q, r)
} }
} }
} }
@ -779,11 +791,26 @@ func TestDecimal_QuoRem2(t *testing.T) {
} }
} }
func sign(d Decimal) int {
return d.value.Sign()
}
// rules for rounded divide, rounded to integer
// rounded_divide(d,d2) = q
// sign q * sign (d/d2) >= 0
// for d and d2 >0 :
// q is already rounded
// q = d/d2 + r , with r > -0.5 and r <= 0.5
// thus q-d/d2 = r, with r > -0.5 and r <= 0.5
// and d2 q -d = r d2 with r d2 > -d2/2 and r d2 <= d2/2
// and 2 (d2 q -d) = x with x > -d2 and x <= d2
// if we factor in precision then x > -d2 * 10^(-precision) and x <= d2 * 10(-precision)
func TestDecimal_DivRound(t *testing.T) { func TestDecimal_DivRound(t *testing.T) {
cases := []struct { cases := []struct {
d string d string
d2 string d2 string
scale int32 prec int32
result string result string
}{ }{
{"2", "2", 0, "1"}, {"2", "2", 0, "1"},
@ -800,9 +827,20 @@ func TestDecimal_DivRound(t *testing.T) {
d, _ := NewFromString(s.d) d, _ := NewFromString(s.d)
d2, _ := NewFromString(s.d2) d2, _ := NewFromString(s.d2)
result, _ := NewFromString(s.result) result, _ := NewFromString(s.result)
q := d.DivRound(d2, s.scale) prec := s.prec
q := d.DivRound(d2, prec)
if sign(q)*sign(d)*sign(d2) < 0 {
t.Errorf("sign of quotient wrong, got: %v/%v is about %v", d, d2, q)
}
x := q.Mul(d2).Abs().Sub(d.Abs()).Mul(New(2, 0))
if x.Cmp(d2.Abs().Mul(New(1, -prec))) > 0 {
t.Errorf("wrong rounding, got: %v/%v prec=%d is about %v", d, d2, prec, q)
}
if x.Cmp(d2.Abs().Mul(New(-1, -prec))) <= 0 {
t.Errorf("wrong rounding, got: %v/%v prec=%d is about %v", d, d2, prec, q)
}
if !q.Equals(result) { if !q.Equals(result) {
t.Errorf("division wrong %s / %s scale %d = %s, got %s", s.d, s.d2, s.scale, s.result, q.String()) t.Errorf("rounded division wrong %s / %s scale %d = %s, got %v", s.d, s.d2, prec, s.result, q)
} }
} }
} }