Result makeEqual(FixedBits& a, FixedBits& b, unsigned from, unsigned to)
{
assert(to >= from);
assert(from <= a.getWidth());
assert(from <= b.getWidth());
Result result = NO_CHANGE;
for (unsigned i = from; i < to; i++)
{
if (a.isFixed(i) && !b.isFixed(i))
{
b.setFixed(i, true);
b.setValue(i, a.getValue(i));
result = CHANGED;
}
else if (b.isFixed(i) && !a.isFixed(i))
{
a.setFixed(i, true);
a.setValue(i, b.getValue(i));
result = CHANGED;
}
else if (b.isFixed(i) && a.isFixed(i))
{
if (a.getValue(i) != b.getValue(i))
return CONFLICT;
}
}
return result;
}
Result bvNotBothWays(FixedBits& a, FixedBits& output)
{
assert(a.getWidth() == output.getWidth());
const int bitWidth = a.getWidth();
Result result = NO_CHANGE;
for (int i = 0; i < bitWidth; i++)
{
// error if they are the same.
if (a.isFixed(i) && output.isFixed(i) &&
(a.getValue(i) == output.getValue(i)))
{
return CONFLICT;
}
if (a.isFixed(i) && !output.isFixed(i))
{
output.setFixed(i, true);
output.setValue(i, !a.getValue(i));
result = CHANGED;
}
if (output.isFixed(i) && !a.isFixed(i))
{
a.setFixed(i, true);
a.setValue(i, !output.getValue(i));
result = CHANGED;
}
}
return result;
}
FixedBits*
ConstantBitPropagation::getUpdatedFixedBits(const ASTNode& n)
{
FixedBits* output = getCurrentFixedBits(n);
const Kind k = n.GetKind();
if (n.isConstant())
{
assert(output->isTotallyFixed());
return output;
}
if (SYMBOL == k)
return output; // No transfer functions for these.
vector<FixedBits*> children;
const int numberOfChildren = n.GetChildren().size();
children.reserve(numberOfChildren);
for (int i = 0; i < numberOfChildren; i++)
{
children.push_back(getCurrentFixedBits(n.GetChildren()[i]));
}
assert(status != CONFLICT);
status = dispatchToTransferFunctions(k, children, *output, n, msm);
//result = dispatchToMaximallyPrecise(k, children, *output, n,msm);
assert(((unsigned)output->getWidth()) == n.GetValueWidth() || output->getWidth() ==1);
return output;
}
Result bvZeroExtendBothWays(vector<FixedBits*>& children, FixedBits& output)
{
assert(children.size() == 2);
// The second argument is a junk size arugment.
FixedBits& input = *children[0];
const int inputBitWidth = input.getWidth();
const int outputBitWidth = output.getWidth();
Result result = makeEqual(input, output, 0, inputBitWidth);
if (CONFLICT == result)
return CONFLICT;
// Fix all the topmost bits of the output to zero.
for (int i = inputBitWidth; i < outputBitWidth; i++)
{
if (output.isFixed(i) && output.getValue(i))
return CONFLICT; // set to one. Never right.
else if (!output.isFixed(i))
{
output.setFixed(i, true);
output.setValue(i, false);
result = CHANGED;
}
}
return result;
}
void setUnsignedMinMax(const FixedBits& v, CBV min, CBV max)
{
CONSTANTBV::BitVector_Fill(max);
CONSTANTBV::BitVector_Empty(min);
for (unsigned i = 0; i < v.getWidth(); i++)
{
if (v.isFixed(i))
{
if (v.getValue(i)) // if it's on. It's on.
{
// CONSTANTBV::BitVector_Bit_On(max, i);
CONSTANTBV::BitVector_Bit_On(min, i);
}
else
{
CONSTANTBV::BitVector_Bit_Off(max, i);
// CONSTANTBV::BitVector_Bit_Off(min, i);
}
}
// else // not fixed. Just set the max.
//{
// CONSTANTBV::BitVector_Bit_On(max, i);
// CONSTANTBV::BitVector_Bit_Off(min, i);
//}
}
assert(CONSTANTBV::BitVector_Lexicompare(min, max) <= 0);
}
// if output bit is true. Fix all the operands.
// if all the operands are fixed. Fix the output.
// given 1,1,1,- == 0, fix - to 0.
Result bvAndBothWays(vector<FixedBits*>& operands, FixedBits& output)
{
Result result = NO_CHANGE;
const int bitWidth = output.getWidth();
for (int i = 0; i < bitWidth; i++)
{
const stats status = getStats(operands, i);
// output is fixed to one. But an input value is false!
if (output.isFixed(i) && output.getValue(i) && status.fixedToZero > 0)
return CONFLICT;
// output is fixed to one. But an input value is false!
if (output.isFixed(i) && !output.getValue(i) && status.fixedToZero == 0 &&
status.unfixed == 0)
return CONFLICT;
// output is fixed to one. So all should be one.
if (output.isFixed(i) && output.getValue(i) && status.unfixed > 0)
{
fixUnfixedTo(operands, i, true);
result = CHANGED;
}
// The output is unfixed. At least one input is false.
if (!output.isFixed(i) && status.fixedToZero > 0)
{
output.setFixed(i, true);
output.setValue(i, false);
result = CHANGED;
}
// Everything is fixed to one!
if (!output.isFixed(i) && status.fixedToZero == 0 && status.unfixed == 0)
{
output.setFixed(i, true);
output.setValue(i, true);
result = CHANGED;
}
// If the output is false, and there is a single unfixed value with
// everything else true..
if (output.isFixed(i) && !output.getValue(i) && status.fixedToZero == 0 &&
status.unfixed == 1)
{
fixUnfixedTo(operands, i, false);
result = CHANGED;
}
}
return result;
}
Result bvExtractBothWays(vector<FixedBits*>& children, FixedBits& output)
{
const size_t numberOfChildren = children.size();
const unsigned outputBitWidth = output.getWidth();
Result result = NO_CHANGE;
assert(3 == numberOfChildren);
unsigned top = children[1]->getUnsignedValue();
unsigned bottom = children[2]->getUnsignedValue();
FixedBits& input = *(children[0]);
assert(top >= bottom);
assert(top - bottom + 1 == outputBitWidth);
assert(top < input.getWidth());
for (unsigned outputPosition = 0; outputPosition < outputBitWidth;
outputPosition++)
{
unsigned inputPosition = outputPosition + bottom;
if (input.isFixed(inputPosition) && output.isFixed(outputPosition))
if (input.getValue(inputPosition) ^ output.getValue(outputPosition))
return CONFLICT;
if (input.isFixed(inputPosition) ^ output.isFixed(outputPosition))
{
if (input.isFixed(inputPosition))
{
output.setFixed(outputPosition, true);
output.setValue(outputPosition, input.getValue(inputPosition));
result = CHANGED;
}
else
{
input.setFixed(inputPosition, true);
input.setValue(inputPosition, output.getValue(outputPosition));
result = CHANGED;
}
}
}
// cerr << "extract[" << top << ":" << bottom << "]" << input << "=" <<
// output<< endl;
return result;
}
Result bvSignExtendBothWays(vector<FixedBits*>& children, FixedBits& output)
{
assert(children.size() == 2);
// The second argument is a junk size arugment.
FixedBits& input = *children[0];
const int inputBitWidth = input.getWidth();
const int outputBitWidth = output.getWidth();
assert(inputBitWidth <= outputBitWidth);
Result result = makeEqual(input, output, 0, inputBitWidth);
if (CONFLICT == result)
return CONFLICT;
// If any of the topmost bits of the output are fixed. Then they all should
// be.
// They should all be fixed to the same value.
bool found = false;
bool setTo;
for (int i = inputBitWidth - /**/ 1 /**/; i < outputBitWidth; i++)
{
if (output.isFixed(i))
{
setTo = output.getValue(i);
found = true;
break;
}
}
if (found)
{
for (int i = inputBitWidth - 1; i < outputBitWidth; i++)
{
if (output.isFixed(i) && (output.getValue(i) != setTo))
return CONFLICT; // if any are set to the wrong value! bad.
else if (!output.isFixed(i))
{
output.setFixed(i, true);
output.setValue(i, setTo);
result = CHANGED;
}
}
Result result2 = makeEqual(input, output, 0, inputBitWidth);
if (CONFLICT == result2)
return CONFLICT;
}
return result;
}
void setSignedMinMax(FixedBits& v, CBV min, CBV max)
{
const unsigned int msb = v.getWidth() - 1;
for (unsigned i = 0; i < (unsigned)v.getWidth(); i++)
{
if (v.isFixed(i))
{
if (v.getValue(i)) // if it's on. It's on.
{
CONSTANTBV::BitVector_Bit_On(max, i);
CONSTANTBV::BitVector_Bit_On(min, i);
}
else
{
CONSTANTBV::BitVector_Bit_Off(max, i);
CONSTANTBV::BitVector_Bit_Off(min, i);
}
}
else
{
if (i != msb)
{ // not fixed. Make the maximum Maximum.
CONSTANTBV::BitVector_Bit_On(max, i);
CONSTANTBV::BitVector_Bit_Off(min, i);
}
else
{ // except for the msb. Where we reduce the min.
CONSTANTBV::BitVector_Bit_On(min, i);
CONSTANTBV::BitVector_Bit_Off(max, i);
}
}
}
assert(CONSTANTBV::BitVector_Compare(min, max) <= 0);
}
Result bvXorBothWays(vector<FixedBits*>& operands, FixedBits& output)
{
Result result = NO_CHANGE;
const int bitWidth = output.getWidth();
for (int i = 0; i < bitWidth; i++)
{
const stats status = getStats(operands, i);
if (status.unfixed == 0) // if they are all fixed. We know the answer.
{
bool answer = (status.fixedToOne % 2) != 0;
if (!output.isFixed(i))
{
output.setFixed(i, true);
output.setValue(i, answer);
result = CHANGED;
}
else if (output.getValue(i) != answer)
return CONFLICT;
}
else if (status.unfixed == 1 && output.isFixed(i))
{
// If there is just one unfixed, and we have the answer --> We know the
// value.
bool soFar = ((status.fixedToOne % 2) != 0);
if (soFar != output.getValue(i))
{ // result needs to be flipped.
fixUnfixedTo(operands, i, true);
}
else
fixUnfixedTo(operands, i, false);
result = CHANGED;
}
}
return result;
}
Result bvAddBothWays(vector<FixedBits*>& children, FixedBits& output)
{
const size_t numberOfChildren = children.size();
if (numberOfChildren==2)
{
return bvAddBothWays(*children[0],*children[1],output);
}
const unsigned bitWidth = output.getWidth();
for (size_t i = 0; i < numberOfChildren; i++)
{
assert(children[i]->getWidth() == bitWidth );
}
int columnL[bitWidth]; // minimum "" ""
int columnH[bitWidth]; // maximum number of true partial products.
initialiseColumnCounts(columnL, columnH, bitWidth, numberOfChildren, children);
int sumH[bitWidth];
int sumL[bitWidth];
sumL[0] = columnL[0];
sumH[0] = columnH[0];
for (unsigned i = /**/1 /**/; i < (unsigned) bitWidth; i++)
{
assert((columnH[i] >= columnL[i]) && (columnL[i] >= 0));
sumH[i] = columnH[i] + (sumH[i - 1] / 2);
sumL[i] = columnL[i] + (sumL[i - 1] / 2);
}
// Now the sums counts are all updated. And consistent with each other.
bool changed = true;
while (changed)
{
changed = false;
// Make sure each column's sum is consistent with the output.
for (unsigned i = 0; i < bitWidth; i++)
{
if (output.isFixed(i))
{
int expected = output.getValue(i) ? 1 : 0;
// output is true. So the maximum and minimum can only be even.
if (sumH[i] % 2 != expected)
{
sumH[i]--;
changed = true;
}
if (sumL[i] % 2 != expected)
{
sumL[i]++;
changed = true;
}
if (changed && ((sumH[i] < sumL[i]) || (sumL[i] < 0)))
return CONFLICT;
}
}
// update the column counts to make them consistent to the totals.
for (unsigned i = /**/0 /**/; i < bitWidth; i++)
{
if (sumH[i] < columnH[i])
{
columnH[i]--;
changed = true;
if (columnH[i] < columnL[i])
return CONFLICT;
}
}
// Go from low to high making each of the sums consistent.
for (unsigned i = /**/1 /**/; i < bitWidth; i++)
{
assert((columnH[i] >= columnL[i]) && (columnL[i] >= 0));
if (sumH[i] > columnH[i] + (sumH[i - 1] / 2))
{
sumH[i] = columnH[i] + (sumH[i - 1] / 2);
changed = true;
}
if (sumL[i] < columnL[i] + (sumL[i - 1] / 2))
{
sumL[i] = columnL[i] + (sumL[i - 1] / 2);
changed = true;
}
if (changed && (sumH[i] < sumL[i] || sumL[i] < 0))
return CONFLICT;
}
// go from high to low, making each of the sums consistent.
for (int i = /**/(int)bitWidth - 1 /**/; i >= 1; i--)
{
if ((sumH[i] == sumL[i]))
{
stats s = getStats(children, i);
if (0 == s.unfixed)
{
// amount that the prior column needs to contribute.
int toContribute = (sumH[i] - s.fixedToOne) * 2;
if (sumH[i - 1] > (toContribute + 1))
{
changed = true;
sumH[i - 1] = toContribute + 1; // plus one because of rounding down.
}
if (sumL[i - 1] < toContribute)
{
changed = true;
sumL[i - 1] = toContribute;
}
if (sumH[i - 1] < sumL[i - 1])
{
return CONFLICT;
}
}
}
}
if (add_debug_messages)
{
std::cerr << "bottom" << std::endl;
cerr << "columnL:";
printArray(columnL, bitWidth);
cerr << "columnH:";
printArray(columnH, bitWidth);
cerr << "sumL:";
printArray(sumL, bitWidth);
cerr << "sumH:";
printArray(sumH, bitWidth);
}
for (unsigned column = 0; column < bitWidth; column++)
{
if (sumH[column] == sumL[column])
{
// (1) If the low and high sum is equal. Then the output is know.
bool newResult = (sumH[column] % 2 == 0) ? false : true;
if (!output.isFixed(column))
{
output.setFixed(column, true);
output.setValue(column, newResult);
changed = true;
}
else if (output.isFixed(column) && (output.getValue(column) != newResult))
return CONFLICT;
// (2) If this column has some unfixed values. Then we may be able to determine them.
Result tempResult;
if (0 == column)
tempResult = fixIfCanForAddition(children, column, sumH[column], 0, 0);
else
tempResult = fixIfCanForAddition(children, column, sumH[column], sumL[column - 1] / 2, sumH[column - 1] / 2);
if (CONFLICT == tempResult)
return CONFLICT;
if (CHANGED == tempResult)
changed = true;
}
}
}
return NOT_IMPLEMENTED;
}
// Specialisation for two operands.
Result
bvAddBothWays(FixedBits& x, FixedBits& y, FixedBits& output)
{
const int bitWidth = output.getWidth();
FixedBits carry(bitWidth + 1, false);
carry.setFixed(0, true);
carry.setValue(0, false);
//cerr << "input" << x << y << output << endl;
for (int i = 0; i < bitWidth; i++)
{
//cerr << i << ":"<< x[i] << y[i] << carry[i] << "=" << output[i]<< endl;
int lb = (x[i] == '1' ? 1 : 0) + (y[i] == '1' ? 1 : 0) + (carry[i] == '1' ? 1 : 0);
int ub = (x[i] == '0' ? 0 : 1) + (y[i] == '0' ? 0 : 1) + (carry[i] == '0' ? 0 : 1);
const int lb_initial = lb;
const int ub_initial = ub;
if (carry[i+1] == '1') // carry out is true.
lb = std::max(2, lb);
if (carry[i+1] == '0') // carry out is false.
ub = std::min(1, ub);
const char output_i = output[i];
if (output_i == '1' && (lb % 2 == 0))
lb++;
if (output_i == '0' && (lb % 2 == 1))
lb++;
if (output_i == '1' && (ub % 2 == 0))
ub--;
if (output_i == '0' && (ub % 2 == 1))
ub--;
if (lb >= 2)
setValue(carry, i+1, true);
if (ub <= 1)
setValue(carry, i+1, false);
if (ub < lb)
return CONFLICT;
if (lb == ub)
{
setValue(output, i, ((lb % 2) == 1));
if (lb_initial ==lb)
{
if (!x.isFixed(i))
setValue(x, i, false);
if (!y.isFixed(i))
setValue(y, i, false);
if (!carry.isFixed(i))
{
setValue(carry, i, false);
i = std::max(i-2,-1); // go back to the prior column.
continue;
}
}
if (ub_initial ==lb)
{
if (!x.isFixed(i))
setValue(x, i, true);
if (!y.isFixed(i))
setValue(y, i, true);
if (!carry.isFixed(i))
{
setValue(carry, i, true);
i = std::max(i-2,-1); // go back to the prior column.
continue;
}
}
}
//cerr << i << "[" << ub << ":" << lb << "]" << endl;
}
return NOT_IMPLEMENTED;
}
// if a==b then fix the result to true.
// if a!=b then fix the result to false.
Result bvEqualsBothWays(FixedBits& a, FixedBits& b, FixedBits& output)
{
assert(a.getWidth() == b.getWidth());
assert(1 == output.getWidth());
const int childWidth = a.getWidth();
Result r = NO_CHANGE;
bool allSame = true;
bool definatelyFalse = false;
for (int i = 0; i < childWidth; i++)
{
// if both fixed
if (a.isFixed(i) && b.isFixed(i))
{
// And have different values.
if (a.getValue(i) != b.getValue(i))
{
definatelyFalse = true;
break;
}
else
{
allSame &= true;
continue;
}
}
allSame &= false;
}
if (definatelyFalse)
{
if (output.isFixed(0) && output.getValue(0))
{
return CONFLICT;
}
else if (!output.isFixed(0))
{
output.setFixed(0, true);
output.setValue(0, false);
r = CHANGED;
}
}
else if (allSame)
{
if (output.isFixed(0) && !output.getValue(0))
{
return CONFLICT;
}
else if (!output.isFixed(0))
{
output.setFixed(0, true);
output.setValue(0, true);
r = CHANGED;
}
}
if (output.isFixed(0) && output.getValue(0)) // all should be the same.
{
for (int i = 0; i < childWidth; i++)
{
if (a.isFixed(i) && b.isFixed(i))
{
if (a.getValue(i) != b.getValue(i))
{
return CONFLICT;
}
}
else if (a.isFixed(i) != b.isFixed(i)) // both same but only one is fixed.
{
if (a.isFixed(i))
{
b.setFixed(i, true);
b.setValue(i, a.getValue(i));
r = CHANGED;
}
else
{
a.setFixed(i, true);
a.setValue(i, b.getValue(i));
r = CHANGED;
}
}
}
}
// if the result is fixed to false, there is a single unspecied value, and all
// the rest are the same. Fix it to the opposite.
if (output.isFixed(0) && !output.getValue(0))
{
int unknown = 0;
for (int i = 0; i < childWidth && unknown < 2; i++)
{
if (!a.isFixed(i))
unknown++;
if (!b.isFixed(i))
unknown++;
else if (a.isFixed(i) && b.isFixed(i) && a.getValue(i) != b.getValue(i))
{
unknown = 10; // hack, don't do the next loop.
break;
}
}
if (1 == unknown)
{
for (int i = 0; i < childWidth; i++)
{
if (!a.isFixed(i))
{
a.setFixed(i, true);
a.setValue(i, !b.getValue(i));
r = CHANGED;
}
if (!b.isFixed(i))
{
b.setFixed(i, true);
b.setValue(i, !a.getValue(i));
r = CHANGED;
}
}
}
}
return r;
}
// If the guard is fixed, make equal the appropriate input and output.
// If one input can not possibly be the output. Then set the guard to make it
// the other one.
// If both values are the same. Set the output to that value.
Result bvITEBothWays(vector<FixedBits*>& children, FixedBits& output)
{
Result result = NO_CHANGE;
assert(3 == children.size());
const int bitWidth = output.getWidth();
FixedBits& guard = *children[0];
FixedBits& c1 = *children[1];
FixedBits& c2 = *children[2];
assert(c1.getWidth() == c2.getWidth());
assert(output.getWidth() == c2.getWidth());
if (guard.isFixed(0) && guard.getValue(0))
{ // guard fixed to true. So make (first arg == output)
result = makeEqual(output, c1, 0, bitWidth);
if (CONFLICT == result)
return CONFLICT;
}
else if (guard.isFixed(0) && !guard.getValue(0))
{
result = makeEqual(output, c2, 0, bitWidth);
if (CONFLICT == result)
return CONFLICT;
}
else
{
for (int i = 0; i < bitWidth; i++)
{
if (c1.isFixed(i) && c2.isFixed(i) && (c1.getValue(i) == c2.getValue(i)))
{
if (output.isFixed(i) && (output.getValue(i) != c1.getValue(i)))
return CONFLICT;
if (!output.isFixed(i))
{
output.setFixed(i, true);
output.setValue(i, c1.getValue(i));
result = CHANGED;
}
}
}
}
bool changed = false;
if (CHANGED == result)
changed = true;
for (int i = 0; i < bitWidth; i++)
{
if (output.isFixed(i))
{
if (c1.isFixed(i) && (c1.getValue(i) != output.getValue(i)))
{
// c1 is fixed to a value that's not the same as the output.
if (!guard.isFixed(0))
{
guard.setFixed(0, true);
guard.setValue(0, false);
result = bvITEBothWays(children, output);
if (CONFLICT == result)
return CONFLICT;
changed = true;
}
else if (guard.getValue(0))
return CONFLICT;
}
if (c2.isFixed(i) && (c2.getValue(i) != output.getValue(i)))
{
// c2 is fixed to a value that's not the same as the output.
if (!guard.isFixed(0))
{
guard.setFixed(0, true);
guard.setValue(0, true);
result = bvITEBothWays(children, output);
if (CONFLICT == result)
return CONFLICT;
changed = true;
}
else if (!guard.getValue(0))
return CONFLICT;
}
}
}
if (result == CONFLICT)
return CONFLICT;
if (changed)
return CHANGED;
return result;
}
Result bvImpliesBothWays(vector<FixedBits*>& children, FixedBits& result)
{
FixedBits& a = (*children[0]);
FixedBits& b = (*children[1]);
assert(a.getWidth() == result.getWidth());
const int bitWidth = a.getWidth();
assert(bitWidth == 1);
Result r = NO_CHANGE;
int i = 0;
// (false -> something) is always true.
// (something -> true ) is always true.
if (a.isFixedToZero(i) || b.isFixedToOne(i))
{
if (!result.isFixed(i))
{
result.setFixed(i, true);
result.setValue(i, true);
r = CHANGED;
}
else if (result.isFixedToZero(i))
return CONFLICT;
}
// If the result is false. it must be (true -> false)
if (result.isFixedToZero(i))
{
if (a.isFixedToZero(i) || b.isFixedToOne(i))
return CONFLICT;
if (!a.isFixed(i))
{
a.setFixed(i, true);
a.setValue(i, true);
r = CHANGED;
}
if (!b.isFixed(i))
{
b.setFixed(i, true);
b.setValue(i, false);
r = CHANGED;
}
}
if (result.isFixedToOne(i))
{
if (a.isFixedToOne(i))
{
if (!b.isFixed(i))
{
b.setFixed(i, true);
b.setValue(i, true);
r = CHANGED;
}
else if (b.isFixedToZero(i))
return CONFLICT;
}
if (b.isFixedToZero(i))
{
if (!a.isFixed(i))
{
a.setFixed(i, true);
a.setValue(i, false);
r = CHANGED;
}
}
}
if (a.isFixedToOne(i) && b.isFixedToZero(i))
{
if (result.isFixedToOne(i))
return CONFLICT;
if (!result.isFixed(i))
{
result.setFixed(i, true);
result.setValue(i, false);
r = CHANGED;
}
}
return r;
}
Result bvOrBothWays(vector<FixedBits*>& children, FixedBits& output)
{
Result r = NO_CHANGE;
const int numberOfChildren = children.size();
const int bitWidth = output.getWidth();
for (int i = 0; i < bitWidth; i++)
{
bool answerKnown = output.isFixed(i);
bool answer = false;
if (answerKnown)
answer = output.getValue(i);
int unks = 0;
int ones = 0;
int zeroes = 0;
for (int j = 0; j < numberOfChildren; j++)
{
assert(output.getWidth() == children[j]->getWidth());
if (!children[j]->isFixed(i))
unks++;
else if (children[j]->getValue(i))
ones++;
else
zeroes++;
}
if (ones > 0) // Atleast a single one found!
{
if (answerKnown && !answer)
return CONFLICT;
if (!answerKnown)
{
output.setFixed(i, true);
output.setValue(i, true);
r = CHANGED;
}
}
if (zeroes == numberOfChildren) // all zeroes.
{
if (answerKnown && answer)
return CONFLICT;
if (!answerKnown)
{
r = CHANGED;
output.setFixed(i, true);
output.setValue(i, false);
}
}
if (answerKnown && !answer) // known false
{
if (ones > 0)
return CONFLICT;
// set all the column to false.
for (int j = 0; j < numberOfChildren; j++)
{
if (!children[j]->isFixed(i))
{
r = CHANGED;
children[j]->setFixed(i, true);
children[j]->setValue(i, false);
}
}
}
if (unks == 1 && answerKnown && answer &&
(zeroes == (numberOfChildren - 1)))
{
// A single unknown, everything else is false. The answer is true. So the
// unknown is true.
for (int j = 0; j < numberOfChildren; j++)
{
if (!children[j]->isFixed(i))
{
r = CHANGED;
children[j]->setFixed(i, true);
children[j]->setValue(i, true);
}
}
}
}
return r;
}