Example usage for org.apache.mahout.math Vector getNumNondefaultElements

Introduction

In this page you can find the example usage for org.apache.mahout.math Vector getNumNondefaultElements.

Prototype

int getNumNondefaultElements();

Source Link

Document

Return the number of values in the recipient which are not the default value.

Usage

From source file:org.gpfvic.mahout.cf.taste.hadoop.item.ToUserVectorsReducer.java

License:Apache License

@Override
protected void reduce(VarLongWritable userID, Iterable<VarLongWritable> itemPrefs, Context context)
        throws IOException, InterruptedException {
    Vector userVector = new RandomAccessSparseVector(Integer.MAX_VALUE, 100);
    for (VarLongWritable itemPref : itemPrefs) {
        int index = TasteHadoopUtils.idToIndex(itemPref.get());
        float value = itemPref instanceof EntityPrefWritable ? ((EntityPrefWritable) itemPref).getPrefValue()
                : 1.0f;// ww w . jav a  2s . c  o m
        userVector.set(index, value);
    }

    if (userVector.getNumNondefaultElements() >= minPreferences) {
        userVectorWritable.set(userVector);
        userVectorWritable.setWritesLaxPrecision(true);
        context.getCounter(Counters.USERS).increment(1);
        context.write(userID, userVectorWritable);
    }
}

From source file:org.gpfvic.mahout.cf.taste.hadoop.item.UserVectorSplitterMapper.java

License:Apache License

private Vector maybePruneUserVector(Vector userVector) {
    if (userVector.getNumNondefaultElements() <= maxPrefsPerUserConsidered) {
        return userVector;
    }/*from w w w.  j  a  va2s.c  o m*/

    float smallestLargeValue = findSmallestLargeValue(userVector);

    // "Blank out" small-sized prefs to reduce the amount of partial products
    // generated later. They're not zeroed, but NaN-ed, so they come through
    // and can be used to exclude these items from prefs.
    for (Element e : userVector.nonZeroes()) {
        float absValue = Math.abs((float) e.get());
        if (absValue < smallestLargeValue) {
            e.set(Float.NaN);
        }
    }

    return userVector;
}

From source file:org.hf.mls.mahout.cf.taste.hadoop.preparation.ToItemVectorsMapper.java

License:Apache License

@Override
protected void map(VarLongWritable rowIndex, VectorWritable vectorWritable, Context ctx)
        throws IOException, InterruptedException {
    Vector userRatings = vectorWritable.get();

    int numElementsBeforeSampling = userRatings.getNumNondefaultElements();
    userRatings = Vectors.maybeSample(userRatings, sampleSize);
    int numElementsAfterSampling = userRatings.getNumNondefaultElements();

    int column = TasteHadoopUtils.idToIndex(rowIndex.get());

    itemVectorWritable.setWritesLaxPrecision(true);

    Vector itemVector = new RandomAccessSparseVector(Integer.MAX_VALUE, 1);
    for (Vector.Element elem : userRatings.nonZeroes()) {
        itemID.set(elem.index());//w  ww .ja v a2 s.  c o  m
        itemVector.setQuick(column, elem.get());
        itemVectorWritable.set(itemVector);
        ctx.write(itemID, itemVectorWritable);
        // reset vector for reuse
        itemVector.setQuick(elem.index(), 0.0);
    }

    ctx.getCounter(Elements.USER_RATINGS_USED).increment(numElementsAfterSampling);
    ctx.getCounter(Elements.USER_RATINGS_NEGLECTED)
            .increment(numElementsBeforeSampling - numElementsAfterSampling);
}