Re: [eigen] Levenberg-marquardt and dogleg minimizer |

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*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] Levenberg-marquardt and dogleg minimizer*From*: Gael Guennebaud <gael.guennebaud@xxxxxxxxx>*Date*: Thu, 26 Feb 2009 13:36:13 +0100*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=KvLMGCnqiNZWbb5qcD2qDgm0F6U9ZQiEtzCXbn7HzxA=; b=Tr4Np9tRI+Hb7gzwaDNCy8oQJB+eprN1tWXcfAyMunZgqV2bFNnceF0dNy3NHE6kRO x1kEQGE9lIgbmVOgbw2IsGlbXw0f0DNFr5lVO0D7B5a1tMG+//bN/v6dCKjDCA1YCufV QqVcfLip54qTUAXaBlVxRRPF5hHpgNVx9zvxw=*Domainkey-signature*: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=YnoXP0LrSiTPplvSLYYwANNIetJDaBmD6M0zrM56X01CpsGiU9Y3+i+qgMVsulDmPm BipcCxS0IsQfr/UoBQsXu8q+f4jfXz1bOioMT/jwgWmgeCToZXfr4A8z4QxOHfjhINaj xC7LXJ2PQ4xfxtL3502rNYLlpeB2FidgqHRWY=

On Thu, Feb 26, 2009 at 1:13 PM, Jos van den Oever <jvdoever@xxxxxxxxx> wrote:

yes, in mind the goal is to be able to instantiate Lev-Marq with sparse-matrices, then the conversion from adolc derivatives to the jacobian will generate a real sparse Jacobian... Note that I think the memory overhead needed by adolc might prevent its use for relatevly large problems.

yes, in forward mode the derivative are more or less computed at compile time using operator overloading, but this is not enough to be able to determine the zeros at compile-time. Likewise, you cannot determine linear parts at compile time, but, at runtime, I think this would be easy to flag the coefficients which are not linear (adolc does not provide that, but this is theoratically possible to add that).

2009/2/26 Gael Guennebaud <gael.guennebaud@xxxxxxxxx>:

> adolc internally uses dense vector to store each derivatives, so itReduced storage in the Jacobian is not the main benefit I'm aiming for.

> cannot deal with large - sparse problem. What would be nice is to

> implement our own autodiff tool based on eigen's dense and sparse

> objects but that happens only if someone interested in doing that

> shows up...

The solver uses a dense Jacobian storage wise, but can do faster

iteration steps if it knows which parts of the Jacobian are zero or

linear.

You are right that using a sparse matrix would probably improve

performance more.

yes, in mind the goal is to be able to instantiate Lev-Marq with sparse-matrices, then the conversion from adolc derivatives to the jacobian will generate a real sparse Jacobian... Note that I think the memory overhead needed by adolc might prevent its use for relatevly large problems.

If I understand the autodiff Jacobian correctly, the derivative

functions are calculated at compile time. So would it be possible to

find out which part of it are zero or linear?

yes, in forward mode the derivative are more or less computed at compile time using operator overloading, but this is not enough to be able to determine the zeros at compile-time. Likewise, you cannot determine linear parts at compile time, but, at runtime, I think this would be easy to flag the coefficients which are not linear (adolc does not provide that, but this is theoratically possible to add that).

Cheers,

Jos

**Follow-Ups**:**Re: [eigen] Levenberg-marquardt and dogleg minimizer***From:*Gael Guennebaud

**References**:**[eigen] Levenberg-marquardt and dogleg minimizer***From:*Keir Mierle

**Re: [eigen] Levenberg-marquardt and dogleg minimizer***From:*Keir Mierle

**Re: [eigen] Levenberg-marquardt and dogleg minimizer***From:*Gael Guennebaud

**Re: [eigen] Levenberg-marquardt and dogleg minimizer***From:*tjhunter

**Re: [eigen] Levenberg-marquardt and dogleg minimizer***From:*Gael Guennebaud

**Re: [eigen] Levenberg-marquardt and dogleg minimizer***From:*Jos van den Oever

**Re: [eigen] Levenberg-marquardt and dogleg minimizer***From:*Gael Guennebaud

**Re: [eigen] Levenberg-marquardt and dogleg minimizer***From:*Jos van den Oever

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