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From "Edward J. Yoon" <edwardy...@apache.org>
Subject Re: Large matrices multiplication problem.
Date Tue, 06 Jan 2009 05:05:51 GMT
```Let's assume matrix a * b of 10,000 * 10,000 dense matrices,

5 * 5 blocks,
1 block is 2000 * 2000 and 16 MB,

0 : c(0, 0) += a(0, 0) * b(0, 0)
1 : c(0, 1) += a(0, 0) * b(0, 1)
...
123 : c(4, 3) += a(4, 4) * b(4, 3)
124 : c(4, 4) += a(4, 4) * b(4, 4)

5^3 * 32 MB = 4 GB.

collection table size is 4 GB. Anyway, let's try it.

On Tue, Jan 6, 2009 at 12:37 PM, Samuel Guo <guosijie@gmail.com> wrote:
> +1
> hmm, it is tricky.
>
> On Tue, Jan 6, 2009 at 11:04 AM, Edward J. Yoon <edwardyoon@apache.org>wrote:
>
>> If we collect blocks to one table during blocking_mapred(), locality
>> will be provided and more faster.
>>
>> row Key   column:A   column:B
>> c(0, 0) += a(0, 0) * b(0, 0)
>> c(0, 0) += a(0, 1) * b(1, 0)
>> c(0, 0) += a(0, 2) * b(2, 0)
>> c(0, 0) += a(0, 3) * b(3, 0)
>> c(0, 1) += a(0, 0) * b(0, 1)
>> c(0, 1) += a(0, 1) * b(1, 1)
>> ...
>>
>> What do you think?
>>
>> On Mon, Jan 5, 2009 at 10:30 AM, Edward J. Yoon <edwardyoon@apache.org>
>> wrote:
>> > Hama Trunk doesn't work for large matrices multiplication with
>> > mapred.task.timeout and scanner.timeout exception. I tried 1,000,000 *
>> > 1,000,000 matrix multiplication on 100 node. (Rests are good)
>> >
>> > To reduce read operation of duplicated block, I thought as describe
>> > below. But, each map processing seems too large.
>> >
>> > ----
>> > // c[i][k] += a[i][j] * b[j][k];
>> >
>> > map() {
>> >  SubMatrix a = value.get();
>> >
>> >  for (RowResult row : scan) {
>> >     collect : c[i][k] = a * b[j][k];
>> >  }
>> > }
>> >
>> > reduce() {
>> >  c[i][k] += c[i][k];
>> > }
>> > ----
>> >
>> > Should we increase {mapred.task.timeout and scanner.timeout}?
>> > or any good idea?
>> >
>> > --
>> > Best Regards, Edward J. Yoon @ NHN, corp.
>> > edwardyoon@apache.org
>> > http://blog.udanax.org
>> >
>>
>>
>>
>> --
>> Best Regards, Edward J. Yoon @ NHN, corp.
>> edwardyoon@apache.org
>> http://blog.udanax.org
>>
>

--
Best Regards, Edward J. Yoon @ NHN, corp.
edwardyoon@apache.org
http://blog.udanax.org

```
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