# Thread: Nouveau Can Beat NVIDIA With Cairo In Select Cases

1. Senior Member
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Originally Posted by mark45
How does one interpret those bars some of which grow downwards some upwards?
The bar represents the cairo-image backend, and being above the bar represents a speedup. As I understood ickle's explanation to me the main differences between the image backend and the xlib backend is that the image backend can't be threaded and doesn't perform the tesselation step (this being a big computational win).

2. Junior Member
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Originally Posted by mark45
"A few orders of magnitude" means "at least a hundred times", do you really mean that?
Actually, common usage of 'order of magnitude' outside of astronomy generally means doubled or halved, so "a few orders of magnitude" would imply at least eight times (doubled three times). In astronomy, where the term originated, an order of magnitude is technically 2.512 (or its inverse, about .398) times so "a few orders of magnitude" would mean at least around 16 times (about 15.851). Sometimes people use 'order of magnitude' to mean 'ten times,' but it's neither the most common nor the most correct meaning.

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Originally Posted by CFWhitman
Actually, common usage of 'order of magnitude' outside of astronomy generally means doubled or halved, so "a few orders of magnitude" would imply at least eight times (doubled three times). In astronomy, where the term originated, an order of magnitude is technically 2.512 (or its inverse, about .398) times so "a few orders of magnitude" would mean at least around 16 times (about 15.851). Sometimes people use 'order of magnitude' to mean 'ten times,' but it's neither the most common nor the most correct meaning.
Que? The 2.512 value comes from Apparant Magnitudes and not from Orders of Magnitude. An order of magnitude is base 10 which means that two orders of magnitude is 100x and three is 1000x.

https://en.wikipedia.org/wiki/Order_of_magnitude

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Originally Posted by F.Ultra
Que? The 2.512 value comes from Apparant Magnitudes and not from Orders of Magnitude. An order of magnitude is base 10 which means that two orders of magnitude is 100x and three is 1000x.

https://en.wikipedia.org/wiki/Order_of_magnitude
I'm not as familiar with the mathematical application as the astronomical one. So you are correct about the common mathematical application. However, it is still not the only meaning. An order of magnitude in astronomy is still 2.512 times. Also, in general, any progression that is based on multiplication rather than addition can be referred to as orders of magnitude (sometimes this is referred to as geometric progression). It's not by any means always ten times (even the article you cited makes this clear).

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Originally Posted by CFWhitman
Also, in general, any progression that is based on multiplication rather than addition can be referred to as orders of magnitude (sometimes this is referred to as geometric progression). It's not by any means always ten times (even the article you cited makes this clear).
In which case the onus falls squarely on the writer to define the term "order of magnitude". In my experience, the term means "power of 10". If the term "order of magnitude" is sufficiently ambiguous that a large percentage of users could genuinely misunderstand it, then it must be defined. If not, then we reduce the problem to what the 'average person' would interpret "order of magnitude" to mean.

For the record, I've never heard of subsequent terms in a geometric progression being referred to as orders of magnitude (for context, I have a Masters degree in Mathematics). It is entirely possible that my university simply didn't use this notation/description, but to suggest that it is standard is, I think, going too far. Descriptive terms such as these were inconsistent even within my own department, so what must they be like throughout the entire world?

As a final plea: when discussing matters of this nature, PLEASE don't cite Wikipedia. No academic would base conclusions on "the journal in which anybody can arbitrarily alter the contents", just as no reasonable doctor would base their medical advice on "the journal of what my friends have seen". Wikipedia is a good resource and what it says should not be dismissed out of hand, but it could almost be the reason for the mantra "trust, but verify.

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