Re: [eigen] Checking for integer overflow in size computations

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On 17.10.2011 00:36, Benoit Jacob wrote:
2011/10/16 Christoph Hertzberg<chtz@xxxxxxxxxxxxxxxxxxxxxxxx>:
On 16.10.2011 22:21, Benoit Jacob wrote:

Note that there is a small performance overhead associated with that.
I tried to minimize it, but there is still 1 integer division in the
size=rows*cols overflow check. I hope that's still negligible compared
to the cost of malloc.

I have not looked into your patch yet, but wouldn't a multiplication in
int64/int128 also do the job?

I don't know that all platforms have an integer type twice bigger than size_t?

On x86-64 are there 128 bit integers? I didn't know that.
Also I'm afraid there might exist 32bit platforms without 64bit integers.

Well, naturally I can't say that for every platform, but for x86-64 it seems to be possible:

If someone really cared, one could implement a backup solution using grid multiplication (where most parts can be ignored, and the case that both high parts are !=0 is trivial)


Dipl.-Inf. Christoph Hertzberg
Cartesium 0.051
Universität Bremen
Enrique-Schmidt-Straße 5
28359 Bremen

Tel: (+49) 421-218-64252

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