Vertex* StringGraphGenerator::addTerminalVertex(const SeqRecord& record)
{
assert(m_pGraph != NULL);
// Build the vertex by performing a full-length search for the
// sequence in the FM-index. We set the ID of the vertex to be the
// lowest index in the returned block list.
OverlapBlockList endBlockList;
m_pOverlapper->alignReadDuplicate(record, &endBlockList);
// Search the block list for the exact match to the end read. This must exist
OverlapBlockList::iterator matchIter = endBlockList.begin();
while(matchIter != endBlockList.end())
{
if(matchIter->numDiff == 0 && !matchIter->flags.isQueryRev())
break; // this block corresponds to the actual sequence of endRead
}
assert(matchIter != endBlockList.end());
// Construct the canonical ID from the matching interval
std::string endID = matchIter->toCanonicalID();
Vertex* pVertex = m_pGraph->getVertex(endID);
if(pVertex == NULL)
{
pVertex = new(m_pGraph->getVertexAllocator()) Vertex(endID, record.seq.toString());
m_pGraph->addVertex(pVertex);
}
return pVertex;
}
// Run the cluster process. If the number of total nodes
// exceeds max, abort the search.
void ReadCluster::run(size_t max)
{
while(!m_queue.empty())
{
if(m_queue.size() + m_outCluster.size() > max)
{
while(!m_queue.empty())
m_queue.pop();
m_outCluster.clear();
return;
}
ClusterNode node = m_queue.front();
m_queue.pop();
// Add this node to the output
m_outCluster.push_back(node);
// Find overlaps for the current node
SeqRecord tempRecord;
tempRecord.id = "cluster";
tempRecord.seq = node.sequence;
OverlapBlockList blockList;
m_pOverlapper->overlapRead(tempRecord, m_minOverlap, &blockList);
// Parse each member of the block list and potentially expand the cluster
for(OverlapBlockList::const_iterator iter = blockList.begin(); iter != blockList.end(); ++iter)
{
// Check if the reads in this block are part of the cluster already
BWTInterval canonicalInterval = iter->getCanonicalInterval();
int64_t canonicalIndex = canonicalInterval.lower;
if(m_usedIndex.count(canonicalIndex) == 0)
{
// This is a new node that isn't in the cluster. Add it.
m_usedIndex.insert(canonicalIndex);
ClusterNode newNode;
newNode.sequence = iter->getFullString(node.sequence);
newNode.interval = canonicalInterval;
newNode.isReverseInterval = iter->flags.isTargetRev();
m_queue.push(newNode);
}
}
}
}
// Return true if the terminalBlock is a substring of any member of blockList
bool OverlapAlgorithm::isBlockSubstring(OverlapBlock& terminalBlock, const OverlapBlockList& blockList, double maxER) const
{
OverlapBlockList::const_iterator iter = blockList.begin();
size_t right_extension_length = terminalBlock.forwardHistory.size();
for(; iter != blockList.end(); ++iter)
{
if(terminalBlock.overlapLen == iter->overlapLen &&
right_extension_length == iter->forwardHistory.size())
{
continue; // same length, cannot be a substring
}
// Calculate error rate between blocks
double er = calculateBlockErrorRate(terminalBlock, *iter);
if(isErrorRateAcceptable(er, maxER))
return true;
}
return false;
}
// Update the overlap block list with a righthand extension to b, removing ranges that become invalid
void OverlapAlgorithm::updateOverlapBlockRangesRight(const BWT* pBWT, const BWT* pRevBWT,
OverlapBlockList& obList, char canonical_base) const
{
OverlapBlockList::iterator iter = obList.begin();
while(iter != obList.end())
{
char relative_base = iter->flags.isQueryComp() ? complement(canonical_base) : canonical_base;
BWTAlgorithms::updateBothR(iter->ranges, relative_base, iter->getExtensionBWT(pBWT, pRevBWT));
// remove the block from the list if its no longer valid
if(!iter->ranges.isValid())
{
iter = obList.erase(iter);
}
else
{
// Add the base to the extension history
int currExtension = iter->forwardHistory.size();
iter->forwardHistory.add(currExtension, canonical_base);
++iter;
}
}
}
void StringGraphGenerator::updateGraphAndQueue(GraphFrontier& currNode, FrontierQueue& queue, OverlapBlockList& blockList)
{
// Partition the block list into containment blocks and extension (valid) blocks
// We do not add containment edges to the graph so the containments are discarded
OverlapBlockList containList;
OverlapBlockList overlapList;
Vertex* pX = currNode.pVertex;
//partitionBlockList(pX->getSeqLen(), &blockList, &overlapList, &containList);
// Process the overlap blocks, adding new vertices and edges where necessary
for(OverlapBlockList::iterator iter = blockList.begin(); iter != blockList.end(); ++iter)
{
if(iter->getEdgeDir() != currNode.dir)
continue;
std::string vertexID = iter->toCanonicalID();
if(vertexID == pX->getID())
continue; // skip self-edges
std::string vertexSeq = iter->getFullString(pX->getSeq().toString());
Overlap o = iter->toOverlap(pX->getID(), vertexID, pX->getSeqLen(), vertexSeq.length());
/*
#if DEBUGGENERATE
std::cout << "has overlap to: " << vertexID << " len: " << iter->overlapLen << " flags: " << iter->flags << "\n";
std::cout << "Overlap string: " << iter->getOverlapString(pX->getSeq().toString()) << "\n";
#endif
*/
// Check if a vertex with endVertexID exists in the graph
Vertex* pVertex = m_pGraph->getVertex(vertexID);
if(pVertex == NULL)
{
#if DEBUGGENERATE
std::cout << "Vertex with ID: " << vertexID << " does not exist, creating\n";
std::cout << "Vertex sequence: " << vertexSeq << "\n";
#endif
// Generate the new vertex
vertexSeq = iter->getFullString(pX->getSeq().toString());
pVertex = new(m_pGraph->getVertexAllocator()) Vertex(vertexID, vertexSeq);
pVertex->setColor(UNEXPLORED_COLOR);
m_pGraph->addVertex(pVertex);
}
// Construct the found edge
Edge* pXY = SGAlgorithms::createEdgesFromOverlap(m_pGraph, o, true);
// If the endpoint vertex is unexplored, queue it
if(pVertex->getColor() == UNEXPLORED_COLOR)
{
GraphFrontier node;
node.pVertex = pVertex;
node.dir = !pXY->getTwin()->getDir(); // continuation direction
node.distance = currNode.distance + pXY->getSeqLen();
if(node.distance <= m_maxDistance)
queue.push(node);
}
}
}
ClusterResult ClusterProcess::process(const SequenceWorkItem& item)
{
// Calculate the intervals in the forward FM-index for this read
const BWT* pBWT = m_pOverlapper->getBWT();
// Check if this read is a substring
OverlapBlockList tempBlockList;
OverlapResult overlapResult = m_pOverlapper->alignReadDuplicate(item.read, &tempBlockList);
if(overlapResult.isSubstring)
{
std::cerr << "Error: substring reads found in sga-cluster. Please run rmdup before cluster\n";
exit(1);
}
// Find the interval in the fm-index containing the read
std::string readString = item.read.seq.toString();
BWTInterval readInterval = BWTAlgorithms::findInterval(pBWT, readString);
BWTAlgorithms::updateInterval(readInterval, '$', pBWT);
// The read must be present in the index
assert(readInterval.isValid());
// Check if this read has been used yet
bool used = false;
for(int64_t i = readInterval.lower; i <= readInterval.upper; ++i)
{
if(m_pMarkedReads->test(i))
{
used = true;
break;
}
}
ClusterResult result;
if(used)
return result; // already part of a cluster, return nothing
// Compute a new cluster around this read
std::set<int64_t> usedIndex;
ClusterNodeQueue queue;
ClusterNode node;
node.sequence = item.read.seq.toString();
node.interval = readInterval;
node.isReverseInterval = false;
usedIndex.insert(readInterval.lower);
queue.push(node);
while(!queue.empty())
{
ClusterNode node = queue.front();
queue.pop();
// Update the used index and the result structure with this node's data
result.clusterNodes.push_back(node);
SeqRecord tempRecord;
tempRecord.id = "cluster";
tempRecord.seq = node.sequence;
OverlapBlockList blockList;
OverlapResult result = m_pOverlapper->overlapRead(tempRecord, m_minOverlap, &blockList);
//m_pOverlapper->buildForwardHistory(&blockList);
// Parse each member of the block list and potentially expand the cluster
for(OverlapBlockList::const_iterator iter = blockList.begin(); iter != blockList.end(); ++iter)
{
// Check if the reads in this block are part of the cluster already
BWTInterval canonicalInterval = iter->getCanonicalInterval();
int64_t canonicalIndex = canonicalInterval.lower;
if(usedIndex.count(canonicalIndex) == 0)
{
usedIndex.insert(canonicalIndex);
ClusterNode newNode;
newNode.sequence = iter->getFullString(node.sequence);
newNode.interval = canonicalInterval;
newNode.isReverseInterval = iter->flags.isTargetRev();
queue.push(newNode);
}
}
}
// If some work was performed, update the bitvector so other threads do not try to merge the same set of reads.
// This uses compare-and-swap instructions to ensure the uppdate is atomic.
// If some other thread has merged this set (and updated
// the bitvector), we discard all the merged data.
// As a given set of reads should all be merged together, we only need to make sure we atomically update
// the bit for the read with the lowest index in the set.
// Sort the intervals into ascending order and remove any duplicate intervals (which can occur
// if the subgraph has a simple cycle)
std::sort(result.clusterNodes.begin(), result.clusterNodes.end(), ClusterNode::compare);
std::vector<ClusterNode>::iterator newEnd = std::unique(result.clusterNodes.begin(),
result.clusterNodes.end(),
ClusterNode::equal);
size_t oldSize = result.clusterNodes.size();
result.clusterNodes.erase(newEnd, result.clusterNodes.end());
size_t newSize = result.clusterNodes.size();
if(oldSize != newSize)
std::cout << "Warning: duplicate cluster nodes were found\n";
// Check if the bit in the vector has already been set for the lowest read index
// If it has some other thread has already output this set so we do nothing
int64_t lowestIndex = result.clusterNodes.front().interval.lower;
bool currentValue = m_pMarkedReads->test(lowestIndex);
bool updateSuccess = false;
if(currentValue == false)
{
// Attempt to update the bit vector with an atomic CAS. If this returns false
// the bit was set by some other thread
updateSuccess = m_pMarkedReads->updateCAS(lowestIndex, currentValue, true);
}
if(updateSuccess)
{
// We successfully atomically set the bit for the first read in this set
// to true. We can safely update the rest of the bits and keep the merged sequences
// for output.
std::vector<ClusterNode>::const_iterator iter = result.clusterNodes.begin();
for(; iter != result.clusterNodes.end(); ++iter)
{
for(int64_t i = iter->interval.lower; i <= iter->interval.upper; ++i)
{
if(i == lowestIndex) //already set
continue;
currentValue = m_pMarkedReads->test(i);
if(currentValue)
{
// This value should not be true, emit a warning
std::cout << "Warning: Bit " << i << " was set outside of critical section\n";
std::cout << "Read: " << readString << "\n";
}
else
{
m_pMarkedReads->updateCAS(i, currentValue, true);
}
}
}
}
else
{
// Some other thread merged these reads already, discard the intermediate
// data and set the result to false
result.clusterNodes.clear();
}
return result;
}
// Extend all the blocks in activeList by one base to the right
// Move all right-terminal blocks to the termainl list. If a block
// is terminal and potentially contained by another block, add it to
// containedList
void OverlapAlgorithm::extendActiveBlocksRight(const BWT* pBWT, const BWT* pRevBWT,
OverlapBlockList& activeList,
OverlapBlockList& terminalList,
OverlapBlockList& /*containedList*/) const
{
OverlapBlockList::iterator iter = activeList.begin();
OverlapBlockList::iterator next;
while(iter != activeList.end())
{
next = iter;
++next;
// Check if block is terminal
AlphaCount64 ext_count = iter->getCanonicalExtCount(pBWT, pRevBWT);
if(ext_count.get('$') > 0)
{
// Only consider this block to be terminal irreducible if it has at least one extension
// or else it is a substring block
if(iter->forwardHistory.size() > 0)
{
OverlapBlock branched = *iter;
BWTAlgorithms::updateBothR(branched.ranges, '$', branched.getExtensionBWT(pBWT, pRevBWT));
terminalList.push_back(branched);
#ifdef DEBUGOVERLAP_2
std::cout << "Block of length " << iter->overlapLen << " moved to terminal\n";
#endif
}
}
int curr_extension = iter->forwardHistory.size();
// Perform the right extensions
// Best case, there is only a single extension character
// Handle this case specially so we don't need to copy the potentially
// large OverlapBlock structure and its full history
if(ext_count.hasUniqueDNAChar())
{
// Get the extension character with respect to the queried sequence
char canonical_base = ext_count.getUniqueDNAChar();
// Flip the base into the frame of reference for the block
char block_base = iter->flags.isQueryComp() ? complement(canonical_base) : canonical_base;
// Update the block using the base in its frame of reference
BWTAlgorithms::updateBothR(iter->ranges, block_base, iter->getExtensionBWT(pBWT, pRevBWT));
// Add the base to the history in the frame of reference of the query read
// This is so the history is consistent when comparing between blocks from different strands
iter->forwardHistory.add(curr_extension, canonical_base);
}
else
{
for(size_t idx = 0; idx < DNA_ALPHABET_SIZE; ++idx)
{
char canonical_base = ALPHABET[idx];
char block_base = iter->flags.isQueryComp() ? complement(canonical_base) : canonical_base;
if(ext_count.get(canonical_base) == 0)
continue;
// Branch the sequence. This involves copying the entire history which can be large
// if the input sequences are very long. This could be avoided by using the SearchHistoyNode/Link
// structure but branches are infrequent enough to not have a large impact
OverlapBlock branched = *iter;
BWTAlgorithms::updateBothR(branched.ranges, block_base, branched.getExtensionBWT(pBWT, pRevBWT));
assert(branched.ranges.isValid());
// Add the base in the canonical frame
branched.forwardHistory.add(curr_extension, canonical_base);
// Insert the new block after the iterator
activeList.insert(iter, branched);
}
// Remove the original block, which has been superceded by the branches
activeList.erase(iter);
}
iter = next; // this skips the newly-inserted blocks
}
}
// Classify the blocks in obList as irreducible, transitive or substrings. The irreducible blocks are
// put into pOBFinal. The remaining are discarded.
// Invariant: the blocks are ordered in descending order of the overlap size so that the longest overlap is first.
void OverlapAlgorithm::_processIrreducibleBlocksInexact(const BWT* pBWT, const BWT* pRevBWT,
OverlapBlockList& activeList,
OverlapBlockList* pOBFinal) const
{
if(activeList.empty())
return;
// The activeList contains all the blocks that are not yet right terminal
// Count the extensions in the top level (longest) blocks first
bool all_eliminated = false;
while(!activeList.empty() && !all_eliminated)
{
// The terminalBlock list contains all the blocks that became right-terminal
// in the current extension round.
OverlapBlockList terminalList;
OverlapBlockList potentialContainedList;
// Perform a single round of extension, any terminal blocks
// are moved to the terminated list
extendActiveBlocksRight(pBWT, pRevBWT, activeList, terminalList, potentialContainedList);
// Compare the blocks in the contained list against the other terminal and active blocks
// If they are a substring match to any of these, discard them
OverlapBlockList::iterator containedIter = potentialContainedList.begin();
for(; containedIter != potentialContainedList.end(); ++containedIter)
{
if(!isBlockSubstring(*containedIter, terminalList, m_errorRate) &&
!isBlockSubstring(*containedIter, activeList, m_errorRate))
{
// Not a substring, move to terminal list
terminalList.push_back(*containedIter);
//std::cout << "Contained block kept: " << containedIter->overlapLen << "\n";
}
else
{
//std::cout << "Contained block found and removed: " << containedIter->overlapLen << "\n";
}
}
// Using the terminated blocks, mark as eliminated any active blocks
// that form a valid overlap to the terminal block. These are transitive edges
// We do not compare two terminal blocks, we don't consider these overlaps to be
// transitive
OverlapBlockList::iterator terminalIter = terminalList.begin();
for(; terminalIter != terminalList.end(); ++terminalIter)
{
#ifdef DEBUGOVERLAP
std::cout << "[II] ***TLB of length " << terminalIter->overlapLen << " has ended\n";
#endif
all_eliminated = true;
OverlapBlockList::iterator activeIter = activeList.begin();
for(; activeIter != activeList.end(); ++activeIter)
{
if(activeIter->isEliminated)
continue; // skip previously marked blocks
// Two conditions must be met for a block to be transitive wrt terminal:
// 1) It must have a strictly shorter overlap than the terminal block
// 2) The error rate between the block and terminal must be less than the threshold
double inferredErrorRate = calculateBlockErrorRate(*terminalIter, *activeIter);
if(activeIter->overlapLen < terminalIter->overlapLen &&
isErrorRateAcceptable(inferredErrorRate, m_errorRate))
{
#ifdef DEBUGOVERLAP_2
std::cout << "Marking block of length " << activeIter->overlapLen << " as eliminated\n";
#endif
activeIter->isEliminated = true;
}
else
{
all_eliminated = false;
}
}
// Move this block to the final list if it has not been previously marked eliminated
if(!terminalIter->isEliminated)
{
#ifdef DEBUGOVERLAP
std::cout << "[II] Adding block " << *terminalIter << " to final list\n";
//std::cout << " extension: " << terminalIter->forwardHistory << "\n";
#endif
pOBFinal->push_back(*terminalIter);
}
}
}
activeList.clear();
}
// Calculate the single right extension to the '$' for each the contained blocks
// so that the interval ranges are consistent
void OverlapAlgorithm::terminateContainedBlocks(OverlapBlockList& containedBlocks) const
{
for(OverlapBlockList::iterator iter = containedBlocks.begin(); iter != containedBlocks.end(); ++iter)
BWTAlgorithms::updateBothR(iter->ranges, '$', iter->getExtensionBWT(m_pBWT, m_pRevBWT));
}
// Construct the set of blocks describing irreducible overlaps with READ
// and write the blocks to pOBOut
OverlapResult OverlapAlgorithm::overlapReadExact(const SeqRecord& read, int minOverlap, OverlapBlockList* pOBOut) const
{
OverlapResult result;
// The complete set of overlap blocks are collected in obWorkingList
// The filtered set (containing only irreducible overlaps) are placed into pOBOut
// by calculateIrreducibleHits
OverlapBlockList obWorkingList;
std::string seq = read.seq.toString();
// We store the various overlap blocks using a number of lists, one for the containments
// in the forward and reverse index and one for each set of overlap blocks
OverlapBlockList oblFwdContain;
OverlapBlockList oblRevContain;
OverlapBlockList oblSuffixFwd;
OverlapBlockList oblSuffixRev;
OverlapBlockList oblPrefixFwd;
OverlapBlockList oblPrefixRev;
// Match the suffix of seq to prefixes
findOverlapBlocksExact(seq, m_pBWT, m_pRevBWT, sufPreAF, minOverlap, &oblSuffixFwd, &oblFwdContain, result);
if (!m_noReverse)
{
findOverlapBlocksExact(complement(seq), m_pRevBWT, m_pBWT, prePreAF, minOverlap, &oblSuffixRev, &oblRevContain, result);
}
// Match the prefix of seq to suffixes
if (!m_noReverse)
{
findOverlapBlocksExact(reverseComplement(seq), m_pBWT, m_pRevBWT, sufSufAF, minOverlap, &oblPrefixFwd, &oblFwdContain, result);
}
findOverlapBlocksExact(reverse(seq), m_pRevBWT, m_pBWT, preSufAF, minOverlap, &oblPrefixRev, &oblRevContain, result);
// Remove submaximal blocks for each block list including fully contained blocks
// Copy the containment blocks into the prefix/suffix lists
oblSuffixFwd.insert(oblSuffixFwd.end(), oblFwdContain.begin(), oblFwdContain.end());
oblPrefixFwd.insert(oblPrefixFwd.end(), oblFwdContain.begin(), oblFwdContain.end());
oblSuffixRev.insert(oblSuffixRev.end(), oblRevContain.begin(), oblRevContain.end());
oblPrefixRev.insert(oblPrefixRev.end(), oblRevContain.begin(), oblRevContain.end());
// Perform the submaximal filter
removeSubMaximalBlocks(&oblSuffixFwd, m_pBWT, m_pRevBWT);
removeSubMaximalBlocks(&oblPrefixFwd, m_pBWT, m_pRevBWT);
removeSubMaximalBlocks(&oblSuffixRev, m_pRevBWT, m_pBWT);
removeSubMaximalBlocks(&oblPrefixRev, m_pRevBWT, m_pBWT);
// Remove the contain blocks from the suffix/prefix lists
removeContainmentBlocks(seq.length(), &oblSuffixFwd);
removeContainmentBlocks(seq.length(), &oblPrefixFwd);
removeContainmentBlocks(seq.length(), &oblSuffixRev);
removeContainmentBlocks(seq.length(), &oblPrefixRev);
// Join the suffix and prefix lists
oblSuffixFwd.splice(oblSuffixFwd.end(), oblSuffixRev);
oblPrefixFwd.splice(oblPrefixFwd.end(), oblPrefixRev);
// Move the containments to the output list
pOBOut->splice(pOBOut->end(), oblFwdContain);
pOBOut->splice(pOBOut->end(), oblRevContain);
// Filter out transitive overlap blocks if requested
if(m_bIrreducible)
{
computeIrreducibleBlocks(m_pBWT, m_pRevBWT, &oblSuffixFwd, pOBOut);
computeIrreducibleBlocks(m_pBWT, m_pRevBWT, &oblPrefixFwd, pOBOut);
}
else
{
pOBOut->splice(pOBOut->end(), oblSuffixFwd);
pOBOut->splice(pOBOut->end(), oblPrefixFwd);
}
return result;
}
