Re: [eigen] Aligned Fixed Sized Mapped matrices |

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*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] Aligned Fixed Sized Mapped matrices*From*: Sameer Agarwal <sameeragarwal@xxxxxxxxxx>*Date*: Sun, 28 Jan 2018 00:44:52 +0000*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=7jULO5vkoX4c/l9TRQ7iFs/gDQBvNUFqaP1pacQZSpY=; b=pf+5NDvvA2QJqMsXH+rqJA1Y8C5Lbzaok3jaoSm1FJYcpRrfY7Wb5Ij321u9jsLr1t F/9hk3eFDfPO3j2dzf/2L7nGrz6feNsiYvALNerQbB2VDy0YwvTRYDHUqElMFakJd2hb VjZinnfKs1uwd/dJ1aDh5mN7hjeoUsoS7OmoiAC20+7SXhPscIy/nacAyHnnk7RhM8AT X2syl5hlHNdcYu9iMl+wzxZfLJO94jWe3vpa0RARC9ZbC53ThisY2slE85ftx+MMBSxr 4p7KWnRYhPDxiRzhUFrVYzTl6u2MRvsRn2fZ3zttLrHTrxaz6nWqATUmxYa+O/A3pgEy zZaQ==

Thanks gael that makes sense.

On Fri, Jan 12, 2018, 2:25 PM Gael Guennebaud <gael.guennebaud@xxxxxxxxx> wrote:

Hi Sameer,it's not really a requirement but a condition that relax the first requirement, it reads:- is the given pointer aligned as specified by the user?- if not, then let's not trigger an assertion if the input data is too small to bother about vectorization (and thus alignment) anyway.I hope that makes more sense now?GaelOn Fri, Jan 12, 2018 at 10:13 PM, Sameer Agarwal <sameeragarwal@xxxxxxxxxx> wrote:I was playing with mapping small fixed aligned buffers to fixed sized matrices and encountered an interesting eigen assertion failure in MapBase.hLine 190 MapBase.h:eigen_assert(( ((internal::UIntPtr(m_data) % internal::traits<Derived>::Alignment) == 0)|| (cols() * rows() * innerStride() * sizeof(Scalar)) < internal::traits<Derived>::Alignment ) && "data is not aligned");I am particularly curious about the requirement(cols() * rows() * innerStride() * sizeof(Scalar)) < internal::traits<Derived>::AlignmentWhy this rather strict requirement?Sameer

**References**:**[eigen] Aligned Fixed Sized Mapped matrices***From:*Sameer Agarwal

**Re: [eigen] Aligned Fixed Sized Mapped matrices***From:*Gael Guennebaud

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