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vm_collatz_test.go
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vm_collatz_test.go
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package stackvm_test
import (
"fmt"
"testing"
. "github.com/jcorbin/stackvm/x"
"github.com/stretchr/testify/require"
)
func TestMach_collatz_sequence(t *testing.T) {
// Test that the vm can generate the collatz sequence from a given starting
// point.
prog, err := Assemble(
".data",
".in", "N:", 0,
".entry", "main:",
":N", "fetch", "dup", // v v :
":seq", "push", // v v i :
"dup", 4, "add", "p2c", // v v i : i=i+4
"storeTo", // v : i
"loop:", // v : i
"dup", 2, "mod", // v v%2 : ...
":odd", "jnz",
"even:",
2, "div", // v/2 : ...
":next", "jump",
"odd:",
3, "mul", 1, "add", // 3*v+1 : ...
"next:",
"dup", // v v : i
"c2p", // v v i :
"dup", // v v i i :
4, "add", // v v i i+4 :
"p2c", // v v i : i=i+4
"storeTo", // v : i
"dup", // v v : i
1, "eq", // v v==1 : i
":loop", "jz", // v : i
"c2p", // v i :
":seq", "push", // v i base :
2, "p2c", // v : i base
"halt",
".data",
"seq:", ".alloc", 16,
)
require.NoError(t, err, "unexpected assembler error")
tcs := make(TestCases, 0, 9)
for n := 1; n < 10; n++ {
// compute the expected collatz sequence for n
vals := []uint32{uint32(n)}
val := vals[0]
for {
switch {
case val%2 == 0:
val = val / 2
default:
val = 3*val + 1
}
vals = append(vals, val)
if val <= 1 {
break
}
}
// build the test case for n
tcs = append(tcs, TestCase{
Name: fmt.Sprintf("collatz(%d)", n),
Prog: prog,
Input: [][]uint32{
[]uint32{uint32(n)},
},
Result: Result{
Values: map[string][]uint32{"unnamed_output_0": vals},
},
})
}
tcs.Run(t)
}
// Test that the vm can reverse explore the collatz recurrence space to some
// depth; initialize a depth counter to 6, then for any given n:
// - always explore 2*n and - if 3 divides n-1 alse explore (n-1)/3
// - accumulate n into memory, like the sequence generator did
// - decrement the depth counter, halting if it reaches 0
var collatzExplore = TestCase{
Name: "gen collatz",
Prog: []interface{}{
6, "push", // d :
":seq", "push", // d i :
":seq", "push", // d i b :
3, "p2c", // : b i d
1, "push", // v=1 : b i d
"round:", // v : b i d
"dup", 1, "sub", 3, "mod", // v (v-1)%3 : b i d
":third", "fz", // v : b i d
"double:", 2, "mul", // v=2*v : b i d
":next", "jump", // ...
"third:", 1, "sub", 3, "div", // v=(v-1)/3 : b i d
"next:", // v : b i d
"dup", 1, "hz", // v : b i d
"dup", // v v : b i d
2, "c2p", // v v d i : b
"dup", 4, "add", "p2c", // v v d i : b i+=4
"swap", // v v i d : b i
"p2c", // v v i : b i d
"storeTo", // v : b i d
"c2p", 1, "sub", // v d-- : b i
"dup", "p2c", 0, "gt", // v d>0 : b i d
":round", "jnz", // v : b i d
"pop", "cpop", "halt", // : b i
".data",
"seq:", ".alloc", 6,
},
Result: Results{
{Values: map[string][]uint32{"unnamed_output_0": {2, 4, 8, 16, 32, 64}}},
{Values: map[string][]uint32{"unnamed_output_0": {2, 4, 8, 16, 5, 10}}},
{Values: map[string][]uint32{"unnamed_output_0": {2, 4, 1, 2, 4, 8}}},
{Values: map[string][]uint32{"unnamed_output_0": {2, 4, 1, 2, 4, 1}}},
}.WithExpectedHaltCodes(1),
}
func TestMach_collatz_explore(t *testing.T) { collatzExplore.Run(t) }
func BenchmarkMach_collatz_explore(b *testing.B) { collatzExplore.Bench(b) }