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https://issues.apache.org/jira/browse/HDFS-7715?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14362660#comment-14362660
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jack liuquan commented on HDFS-7715:
------------------------------------
Hi Rashmi,
Thanks for your respones.
I make a code modification of remainderWithPBCalcXOR() in GaloisField.java,
and make Hitchhiker-XOR+ not relying the all-XOR-parity property of underlying
RS code.
Can you review my code below and check whether it is OK ?
Thank you very much!
===========
public void remainderWithPBCalcXOR(byte[][] dividend, int[] divisor, byte[][]
piggys,
int[] piggyBackSetSizes, int pb_vec, int stripeSize, int
paritySize) {
...
...
// add for hitchhiker-XOR+, no need the all-XOR-parity property.
// calc all-XOR of all first substrip data units
int piggys_pbvec = 0;
for (int m = paritySize; m < dividend.length; ++m) {
piggys_pbvec = (piggys_pbvec ^ dividend[m][k]);
}
for (int i = dividend.length - divisor.length; i >= 0; i--) {
for (int j = 0; j < divisor.length; j++) {
//calculate the parities
int ratio =
divTable[dividend[i +
divisor.length - 1][k] & 0x00FF][divisor[divisor.length - 1]];
dividend[j + i][k] = (byte)((dividend[j + i][k]
& 0x00FF) ^ mulTable[ratio][divisor[j]]);
}
}
dividend[pb_vec][k] = (byte)piggys_pbvec;
}
This modification may sacrifice a little performance.
> Implement the Hitchhiker erasure coding algorithm
> -------------------------------------------------
>
> Key: HDFS-7715
> URL: https://issues.apache.org/jira/browse/HDFS-7715
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Zhe Zhang
> Assignee: jack liuquan
>
> [Hitchhiker |
> http://www.eecs.berkeley.edu/~nihar/publications/Hitchhiker_SIGCOMM14.pdf] is
> a new erasure coding algorithm developed as a research project at UC
> Berkeley. It has been shown to reduce network traffic and disk I/O by 25%-45%
> during data reconstruction. This JIRA aims to introduce Hitchhiker to the
> HDFS-EC framework, as one of the pluggable codec algorithms.
> The existing implementation is based on HDFS-RAID.
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