Re: [sqlite] sparse matrix in scientific computing with sqlite

Michael Chen wrote: > --this is my first version for the purpose of storing sparse numerical > matrix in sql > --please let me know how to fix the bug at the end of the file, and how to > tune the performance > --or any better reference, thanks! > > .explain--

Re: [sqlite] sparse matrix in scientific computing with sqlite

yes, that's what I am thinking of too. This big table is in charge of store all matrix, keep track of all index changes, and rollback when needed. I will only extract a tiny part from this big table in format like a sparse matrix, and put it in C array, then the available numerical routines, such

Re: [sqlite] sparse matrix in scientific computing with sqlite

On Fri, Oct 16, 2009 at 1:41 PM, Michael Chen wrote: > rdbms is indeed not a place for store a single sparse matrix like this. > However I have hundreds of them, and I need to break them and recombine them > frequently; furthermore, I need to drop a few rows or

Re: [sqlite] sparse matrix in scientific computing with sqlite

rdbms is indeed not a place for store a single sparse matrix like this. However I have hundreds of them, and I need to break them and recombine them frequently; furthermore, I need to drop a few rows or columns successively, and need to be able to trace back what's a row's original index. I think

Re: [sqlite] sparse matrix in scientific computing with sqlite

thanks Pavel ! On Fri, Oct 16, 2009 at 1:24 PM, Pavel Ivanov wrote: > > -- IA = [ 1 3 5 7 ] // IA(i) = Index of the first nonzero element > of > > row i in A > > Why 4th element if A has only 3 rows? > > > create temp view rowwiseC as > > select a1.rowid, sum(a2.ct) +1

Re: [sqlite] Sparse matrix

Hi All, Simon answered: Here's a less gruesome version - no cases. I've given no thought to performance comparisons. Thanks for the two great solutions you posted. Upon further investigation, those solutions assume that we want all like occurrences together, effectively sorting records

Re: [sqlite] Sparse matrix

At 1:54 PM +1000 8/23/07, T wrote: Hi Darren, It seems to me that you have a flawed design. Displaying sparse like that should be a function of your application display code, not the database I had to chuckle that when I asked "How do I use this to do that", your solution was "you shouldn't

Re: [sqlite] Sparse matrix

Hi Darren, It seems to me that you have a flawed design. Displaying sparse like that should be a function of your application display code, not the database I had to chuckle that when I asked "How do I use this to do that", your solution was "you shouldn't have that and you should do it

Re: [sqlite] Sparse matrix

Hi Simon, Here's a less gruesome version - no cases. I've given no thought to performance comparisons. Thanks for the two great solutions you posted. They certainly achieve the desired result with the simplified sample I gave. However, in the broader reality, it doesn't quite satisfy my

Re: [sqlite] Sparse matrix

Hi Tom, Here's a less gruesome version - no cases. I've given no thought to performance comparisons. C:\Joinerysoft\JMS\dev\trunk> sqlite3 tst.db SQLite version 3.4.0 Enter ".help" for instructions sqlite> insert into List values( 'a' ); sqlite> insert into List values( 'a' ); sqlite> insert

Re: [sqlite] Sparse matrix

Hi Tom, Its a pretty gruesome bit of sql... C:\Joinerysoft\JMS\dev\trunk> sqlite3 tst.db SQLite version 3.4.0 Enter ".help" for instructions sqlite> create table List( Code text ); sqlite> insert into List values( 'a' ); sqlite> insert into List values( 'a' ); sqlite> insert into List values(

Re: [sqlite] Sparse matrix

It seems to me that you have a flawed design. You should just have a 2 column database to begin with, with a table like this: Code Count a 4 b 2 c 3 Rather than plain inserting or deleting rows, just sometimes insert or delete, you should instead increment or decrement

[sqlite] Sparse matrix

Hi all, OK, this one has me stumped. I've been staring at it too long. I have a table with a column like this: Code a a a a b b c c c I want to output two columns, one showing the Code, another showing the count of each code, but with a null wherever it was a repeat, like this: Code