[Clp] How is the barrier method initialized?

[Bo Jensen]

On Thu, Oct 25, 2012 at 8:55 PM, John Forrest
<john.forrest at fastercoin.com>wrote:

> Bo,
>
> Directly - very little of OSL.  As in - read what OSL does and then do the
> same/different - a great deal.
>
> The Coin-OR initiative was started at ISMP 2000 with me as "benevolent
> dictator" i.e. doing nothing.  Osi solver interface came first and Cgl.
>  However a need arose for a factorization (for Gomory cuts) and I had
> written a "child of OSL" code to do structured parallel simplex.  I
> simplified the factorization from that (which explains some of the quirks).
>
> Having a factorization, it was natural to start on Clp.  Basically the
> idea was to learn from the mistakes of OSL and make brand new mistakes.
>
> With Clp there had to be an OsiClp.  The Osi interface specified a branch
> and bound function.  So how hard can it be to write a Simple Branch and
> Bound code?  I guessed 8 hours but it took 12. This became SBB but a) there
> was already some software called SBB and b) it stopped being simple - so
> Cbc.
>
> For medium sized problems Clp was slower than OSL had been so I lifted the
> OSL factorization code and made it into an alternative factorization
> CoinOslFactorization.  So that is the only piece directly from OSL.  OSL
> itself was an IBM product from a Research code YKTLP which was made into a
> product as a large oil company said they would buy an IBM mainframe plus
> Vector Feature rather than a cheaper lookalike mainframe IF YKTLP became a
> product.  OSL was in Fortran (1987?) and later converted to C by a program
> f2c which does not produce elegant code (but then I have never been accused
> of writing elegant code).
>
> I can hear the sound of snoring - but I hope that answers your question.


Thanks you did, not snoring at all, I love such software stories.


>
>
> John Forrest
>
>
> On 25/10/12 17:57, Bo Jensen wrote:
>
>> John,
>>
>> Just out of curiosity, what's the history of CLP/CBC/OSL, I mean how much
>> of OSL were reused in some form ?
>>
>> /Bo
>>
>>
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