Thank you for this analysis. I can't immediately confirm this since it's
been a while but this sounds credible.
Do you mind to file a jira with all this information, and even perhaps do a
PR on github?
thank you.
On Mon, Apr 27, 2015 at 4:32 AM, lastarsenal <lastarse...@163.com> wrote:
> Hi, All,
>
>
> Recently, I tried mahout's hadoop ssvd(mahout-0.9 or mahout-1.0)
> job. There's a java heap space out of memory problem in ABtDenseOutJob. I
> found the reason, the ABtDenseOutJob map code is as below:
>
>
> protected void map(Writable key, VectorWritable value, Context context)
> throws IOException, InterruptedException {
>
>
> Vector vec = value.get();
>
>
> int vecSize = vec.size();
> if (aCols == null) {
> aCols = new Vector[vecSize];
> } else if (aCols.length < vecSize) {
> aCols = Arrays.copyOf(aCols, vecSize);
> }
>
>
> if (vec.isDense()) {
> for (int i = 0; i < vecSize; i++) {
> extendAColIfNeeded(i, aRowCount + 1);
> aCols[i].setQuick(aRowCount, vec.getQuick(i));
> }
> } else if (vec.size() > 0) {
> for (Vector.Element vecEl : vec.nonZeroes()) {
> int i = vecEl.index();
> extendAColIfNeeded(i, aRowCount + 1);
> aCols[i].setQuick(aRowCount, vecEl.get());
> }
> }
> aRowCount++;
> }
>
>
> If the input is RandomAccessSparseVector, usually with big data, it's
> vec.size() is Integer.MAX_VALUE, which is 2^31, then aCols = new
> Vector[vecSize] will introduce the OutOfMemory problem. The settlement of
> course should be enlarge every tasktracker's maximum memory:
> <property>
> <name>mapred.child.java.opts</name>
> <value>-Xmx1024m</value>
> </property>
> However, if you are NOT hadoop administrator or ops, you have no
> permission to modify the config. So, I try to modify ABtDenseOutJob map
> code to support RandomAccessSparseVector situation, I use hashmap to
> represent aCols instead of the original Vector[] aCols array, the modified
> code is as below:
>
>
> private Map<Integer, Vector> aColsMap = new HashMap<Integer, Vector>();
> protected void map(Writable key, VectorWritable value, Context context)
> throws IOException, InterruptedException {
>
>
> Vector vec = value.get();
> if (vec.isDense()) {
> for (int i = 0; i < vecSize; i++) {
> //extendAColIfNeeded(i, aRowCount + 1);
> if (aColsMap.get(i) == null) {
> aColsMap.put(i, new RandomAccessSparseVector(Integer.MAX_VALUE,
> 100));
> }
> aColsMap.get(i).setQuick(aRowCount, vec.getQuick(i));
> //aCols[i].setQuick(aRowCount, vec.getQuick(i));
> }
> } else if (vec.size() > 0) {
> for (Vector.Element vecEl : vec.nonZeroes()) {
> int i = vecEl.index();
> //extendAColIfNeeded(i, aRowCount + 1);
> if (aColsMap.get(i) == null) {
> aColsMap.put(i, new RandomAccessSparseVector(Integer.MAX_VALUE,
> 100));
> }
> aColsMap.get(i).setQuick(aRowCount, vecEl.get());
> //aCols[i].setQuick(aRowCount, vecEl.get());
> }
> }
> aRowCount++;
> }
>
>
> Then the OutofMemory problem is dismissed.
>
>
> Thank you!
>
>
