org.apfloat.internal.FloatCarryCRTStepStrategy Maven / Gradle / Ivy
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package org.apfloat.internal;
import java.math.BigInteger;
import org.apfloat.ApfloatRuntimeException;
import org.apfloat.spi.CarryCRTStepStrategy;
import org.apfloat.spi.DataStorage;
import static org.apfloat.internal.FloatModConstants.*;
/**
* Class for performing the final steps of a three-modulus
* Number Theoretic Transform based convolution. Works for the
* float type.
*
* All access to this class must be externally synchronized.
*
* @since 1.7.0
* @version 1.8.0
* @author Mikko Tommila
*/
public class FloatCarryCRTStepStrategy
extends FloatCRTMath
implements CarryCRTStepStrategy
{
/**
* Creates a carry-CRT steps object using the specified radix.
*
* @param radix The radix that will be used.
*/
public FloatCarryCRTStepStrategy(int radix)
{
super(radix);
}
public float[] crt(DataStorage resultMod0, DataStorage resultMod1, DataStorage resultMod2, DataStorage dataStorage, long size, long resultSize, long offset, long length)
throws ApfloatRuntimeException
{
long skipSize = (offset == 0 ? size - resultSize + 1: 0); // For the first block, ignore the first 1-3 elements
long lastSize = (offset + length == size ? 1: 0); // For the last block, add 1 element
long nonLastSize = 1 - lastSize; // For the other than last blocks, move 1 element
long subResultSize = length - skipSize + lastSize;
long subStart = size - offset,
subEnd = subStart - length,
subResultStart = size - offset - length + nonLastSize + subResultSize,
subResultEnd = subResultStart - subResultSize;
DataStorage.Iterator src0 = resultMod0.iterator(DataStorage.READ, subStart, subEnd),
src1 = resultMod1.iterator(DataStorage.READ, subStart, subEnd),
src2 = resultMod2.iterator(DataStorage.READ, subStart, subEnd),
dst = dataStorage.iterator(DataStorage.WRITE, subResultStart, subResultEnd);
float[] carryResult = new float[3],
sum = new float[3],
tmp = new float[3];
// Preliminary carry-CRT calculation (happens in parallel in multiple blocks)
for (long i = 0; i < length; i++)
{
float y0 = MATH_MOD_0.modMultiply(T0, src0.getFloat()),
y1 = MATH_MOD_1.modMultiply(T1, src1.getFloat()),
y2 = MATH_MOD_2.modMultiply(T2, src2.getFloat());
multiply(M12, y0, sum);
multiply(M02, y1, tmp);
if (add(tmp, sum) != 0 ||
compare(sum, M012) >= 0)
{
subtract(M012, sum);
}
multiply(M01, y2, tmp);
if (add(tmp, sum) != 0 ||
compare(sum, M012) >= 0)
{
subtract(M012, sum);
}
add(sum, carryResult);
float result = divide(carryResult);
// In the first block, ignore the first element (it's zero in full precision calculations)
// and possibly one or two more in limited precision calculations
if (i >= skipSize)
{
dst.setFloat(result);
dst.next();
}
src0.next();
src1.next();
src2.next();
}
// Calculate the last words (in base math)
float result0 = divide(carryResult);
float result1 = carryResult[2];
assert (carryResult[0] == 0);
assert (carryResult[1] == 0);
// Last block has one extra element (corresponding to the one skipped in the first block)
if (subResultSize == length - skipSize + 1)
{
dst.setFloat(result0);
dst.close();
result0 = result1;
assert (result1 == 0);
}
float[] results = { result1, result0 };
return results;
}
public float[] carry(DataStorage dataStorage, long size, long resultSize, long offset, long length, float[] results, float[] previousResults)
throws ApfloatRuntimeException
{
long skipSize = (offset == 0 ? size - resultSize + 1: 0); // For the first block, ignore the first 1-3 elements
long lastSize = (offset + length == size ? 1: 0); // For the last block, add 1 element
long nonLastSize = 1 - lastSize; // For the other than last blocks, move 1 element
long subResultSize = length - skipSize + lastSize;
long subResultStart = size - offset - length + nonLastSize + subResultSize,
subResultEnd = subResultStart - subResultSize;
// Get iterators for the previous block carries, and dst, padded with this block's carries
// Note that size could be 1 but carries size is 2
DataStorage.Iterator src = arrayIterator(previousResults);
DataStorage.Iterator dst = compositeIterator(dataStorage.iterator(DataStorage.READ_WRITE, subResultStart, subResultEnd), subResultSize, arrayIterator(results));
// Propagate base addition through dst, and this block's carries
float carry = baseAdd(dst, src, 0, dst, previousResults.length);
carry = baseCarry(dst, carry, subResultSize);
dst.close(); // Iterator likely was not iterated to end
assert (carry == 0);
return results;
}
private float baseCarry(DataStorage.Iterator srcDst, float carry, long size)
throws ApfloatRuntimeException
{
for (long i = 0; i < size && carry > 0; i++)
{
carry = baseAdd(srcDst, null, carry, srcDst, 1);
}
return carry;
}
// Wrap an array in a simple reverse-order iterator, padded with zeros
private static DataStorage.Iterator arrayIterator(final float[] data)
{
return new DataStorage.Iterator()
{
public boolean hasNext()
{
return true;
}
public void next()
{
this.position--;
}
public float getFloat()
{
assert (this.position >= 0);
return data[this.position];
}
public void setFloat(float value)
{
assert (this.position >= 0);
data[this.position] = value;
}
private static final long serialVersionUID = 1L;
private int position = data.length - 1;
};
}
// Composite iterator, made by concatenating two iterators
private static DataStorage.Iterator compositeIterator(final DataStorage.Iterator iterator1, final long size, final DataStorage.Iterator iterator2)
{
return new DataStorage.Iterator()
{
public boolean hasNext()
{
return (this.position < size ? iterator1.hasNext() : iterator2.hasNext());
}
public void next()
throws ApfloatRuntimeException
{
(this.position < size ? iterator1 : iterator2).next();
this.position++;
}
public float getFloat()
throws ApfloatRuntimeException
{
return (this.position < size ? iterator1 : iterator2).getFloat();
}
public void setFloat(float value)
throws ApfloatRuntimeException
{
(this.position < size ? iterator1 : iterator2).setFloat(value);
}
public void close()
throws ApfloatRuntimeException
{
(this.position < size ? iterator1 : iterator2).close();
}
private static final long serialVersionUID = 1L;
private long position;
};
}
private static final long serialVersionUID = 3192182234524626533L;
private static final FloatModMath MATH_MOD_0,
MATH_MOD_1,
MATH_MOD_2;
private static final float T0,
T1,
T2;
private static final float[] M01,
M02,
M12,
M012;
static
{
MATH_MOD_0 = new FloatModMath();
MATH_MOD_1 = new FloatModMath();
MATH_MOD_2 = new FloatModMath();
MATH_MOD_0.setModulus(MODULUS[0]);
MATH_MOD_1.setModulus(MODULUS[1]);
MATH_MOD_2.setModulus(MODULUS[2]);
// Probably sub-optimal, but it's a one-time operation
BigInteger base = BigInteger.valueOf(Math.abs((long) MAX_POWER_OF_TWO_BASE)), // In int case the base is 0x80000000
m0 = BigInteger.valueOf((long) MODULUS[0]),
m1 = BigInteger.valueOf((long) MODULUS[1]),
m2 = BigInteger.valueOf((long) MODULUS[2]),
m01 = m0.multiply(m1),
m02 = m0.multiply(m2),
m12 = m1.multiply(m2);
T0 = m12.modInverse(m0).floatValue();
T1 = m02.modInverse(m1).floatValue();
T2 = m01.modInverse(m2).floatValue();
M01 = new float[2];
M02 = new float[2];
M12 = new float[2];
M012 = new float[3];
BigInteger[] qr = m01.divideAndRemainder(base);
M01[0] = qr[0].floatValue();
M01[1] = qr[1].floatValue();
qr = m02.divideAndRemainder(base);
M02[0] = qr[0].floatValue();
M02[1] = qr[1].floatValue();
qr = m12.divideAndRemainder(base);
M12[0] = qr[0].floatValue();
M12[1] = qr[1].floatValue();
qr = m0.multiply(m12).divideAndRemainder(base);
M012[2] = qr[1].floatValue();
qr = qr[0].divideAndRemainder(base);
M012[0] = qr[0].floatValue();
M012[1] = qr[1].floatValue();
}
}