Mailman 3 February 2003 - NumPy-Discussion

byteswap() not doing anything !?
by Sebastian Haase 20 Feb '03

20 Feb '03

>>> xx = na.array((1,2,3)) >>> xx array([1, 2, 3]) >>> xx.byteswap() >>> xx array([1, 2, 3]) >>> xx.type() Int32 Hi all, I was reading the documentation for array 0.4 but I get the about results. How do I get the bytes swaped like it says in the manual: numbyteswap() The byteswap method performs a byte swapping operation on all the elements in the array, working inplace (i.e. it returns None). >>> print a [1 2 3] >>> a.byteswap() >>> print a [16777216 33554432 50331648] Thanks, Sebastian

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range check: feature request for numarray
by Francesc Alted 20 Feb '03

20 Feb '03

Hi, I think it would be useful to provide some range checking in numarray. For example, right now, you can do: In [24]: a=numarray.array([1,2],numarray.Int8) In [25]: a[1] = 256 In [26]: a Out[26]: array([1, 0], type=Int8) and nothing happens. But I'm proposing to raise an OverflowWarning so that people can be aware of such range overflows. Maybe it is desirable that the default would be to not issue the warning, except when the user wanted to know about that. So, my proposal is that the actual behaviour should be mantained, but when you want to be aware of all the warnings something like this could happen: In [28]: warnings.resetwarnings() In [29]: a=numarray.array([1,2],numarray.Int8) In [30]: a[1] = 256 OverflowWarning: value assignment not in the type range In [31]: a Out[31]: array([1, 0], type=Int8) But perhaps this feature might slow a bit the performance of assignments. Regards, -- Francesc Alted `` We are shaped by our thoughts, we become what we think. When the mind is pure, joy follows like a shadow that never leaves. '' -- Buddha, The Dhammapada

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rank-0 chararrays?
by Francesc Alted 18 Feb '03

18 Feb '03

Hi, I'm trying to map Numeric character typecode ('c') to chararrays, but I have a problem to distinguish between In [109]: chararray.array("qqqq") Out[109]: CharArray(['qqqq']) and In [110]: chararray.array(["qqqq"]) # Note the extra "[" "]" Out[110]: CharArray(['qqqq']) # The same result as 109 while in Numeric we have: In [113]: Numeric.array("qqqq") Out[113]: array([q, q, q, q],'c') In [114]: Numeric.array(["qqqq"]) Out[114]: array([ [q, q, q, q]],'c') # Differs from 113 even in numarray objects, rank-0 seems to work well: In [107]: numarray.array(1) Out[107]: array(1) In [108]: numarray.array([1]) Out[108]: array([1]) # Objects differ So, it seems like if chararray does not support well rank-0 objects. Is this the expected behavior?. If yes, we have no possibility to distinguish between object 109 and 110, and I'd like to distinguish between this two. What can be done to achieve this? Thanks, -- Francesc Alted

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Psymeric-update
by Tim Hochberg 17 Feb '03

17 Feb '03

The good news is Psymeric now supports complex numbers and inplace addition and complex numbers (Complex32 and Complex64). Also by doing some tuning, I got the overhead of Psymeric down to less than three times that of Numeric (versus 20 times in the version of Numarray that I have). Even without Psyco, the code only has overhead of five and half times that of Numeric, so it seems that the Numarray folks should at least be able to get down to that level without throwing everything into C. I have not been able to increase the asymptoptic speed and I think I'm probably stuck on that front for the time being. For the most part Psymeric is close to Numeric for large arrays, which makes it about 50% faster than numarray for noncontiguous and half as fast for contiguous arrays. These timings are for Float64: for Int8, Psymeric is ~3x slower than Numeric and for Int16 it's 50% slower, for Int32 2x slower. Psymeric is very slow for Float32 and Complex32 (~10x slower than Numeric) beacause of some Psyco issues with array.arrays and floats which I expect will be fixed at some point. And finally, for Complex64, psymeric is comparable to Numeric for addition and subtraction, but almost half as fast for multiplication and almost a third as fast for division. Barring some further improvements in Psyco or some new insights on my part, this is probably as far as I'll go with this. At this point, it would probably not be hard to make this into a work alike for Numeric or Numarray (excluding the various extension modules: FFT and the like). The one relatively hard part still outstanding it ufunc.accumulate/reduce. However, the performance while very impressive for an essentially pure python solution is not good enough to motivate me to use this in preference to Numeric. If anyone is interested in looking at the code, I'd be happy to send it to them. Regards, -tim

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ESTRADA [HELP]
by MRS L ESTRADA 14 Feb '03

14 Feb '03

Dear sir My name is LOUISA C.ESTRADA,The wife of Mr. JOSEPH ESTRADA, the former President of Philippines located in the South East Asia. My husband was recently impeached from office by a backed uprising of mass demonstrators and the Senate. My husband is presently in jail and facing trial on charges of corruption, embezzlement, and the mysterious charge of plunder which might lead to death sentence. The present government is forcing my husband out of manila to avoid demonstration by his supporters. During my husband's regime as president of Philippine, I realized some reasonable amount of money from various deals that I successfully executed. I have plans to invest this money for my children's future on real estate and industrial production. My husband is not aware of this because I wish to do it secretly for now. Before my husband was impeached, I secretly siphoned the sum of $30,000,000 million USD (Thirty million United states dollars) out of Philippines and deposited the money with a security firm that transports valuable goods and consignments through diplomatic means. I also declared that the consignment was solid gold and my foreign business partner owned it. I am contacting you because I want you to go to the security company and claim the money on my behalf since I have declared that the consignment belong to my foreign business partner. You shall also be required to assist me in investment in your country. I hope to trust you as a God fearing person who will not sit on this money when you claim it, rather assist me properly, I expect you to declare what percentage of the total money you will take for your assistance. When I receive your positive response I will let you know where the security company is and the payment pin code to claim the money which is very important. For now, let all our communication be by e-mail because my line are right now connected to the Philippines Telecommunication Network services. Please also send me your telephone and fax number. I will ask my son to contact you to give you more details on after i have received a responce from you. Thank you and God bless you and your family. MRS LOUISA C. ESTRADA

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PEP-242 Numeric kinds -- disposition
by Paul Dubois 13 Feb '03

13 Feb '03

PEP-242 should be closed. The kinds module will not be added to the standard library. There was no opposition to the proposal but only mild interest in using it, not enough to justify adding the module to the standard library. Instead, it will be made available as a separate distribution item at the Numerical Python site. At the next release of Numerical Python, it will no longer be a part of the Numeric distribution.

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OSCON / Python 11 proposals deadline is February 15th!
by Guido van Rossum 13 Feb '03

13 Feb '03

The Python 11 Conference is being held July 7-11 in Portland, Oregon as part of OSCON 2003. http://conferences.oreillynet.com/os2003/ The deadline for proposals is February 15th! You only need to have your proposal in this week, you don't need to worry about trying to put together the complete presentation or tutorial materials at this time. Proposal submissions page: http://conferences.oreillynet.com/cs/os2003/create/e_sess Few proposals have been submitted so far, we need many more to have a successful Python 11 conference. If you have submitted a proposal for one of the other Python conferences this year such as PyCon, I encourage you to go ahead and submit the proposal to Python 11 as well. If you are presenting at the Python UK Conference or EuroPython, but are unable to attend Python 11, you should consider having another team member do the presentation. The theme of OSCON 2003 is "Embracing and Extending Proprietary Software". Papers and presentations on how to successfully transition away from proprietary software would also be good, but it is not necessary for your proposal to cover the theme, proposals just need to be related to Python. COMPENSATION: Free registration for speakers (except lightning talks). Tutorial speakers also get: $500 honorarium; $50 per diem on day of tutorial; 1 night hotel; airfare. O'REILLY ANNOUNCEMENT: 2003 O'Reilly Open Source Convention Call For Participation Embracing and Extending Proprietary Software http://conferences.oreilly.com/oscon/ O'Reilly & Associates invites programmers, developers, strategists, and technical staff to submit proposals to lead tutorial and conference sessions at the 2003 Open Source Software Convention, slated for July 7-11 in Portland, OR. Proposals are due February 15, 2003. For more information please visit our OSCON website http://conferences.oreilly.com/oscon/ The theme this year is "Embracing and Extending Proprietary Software." Few companies use only one vendor's software on desktops, back office, and servers. Variety in operating systems and applications is becoming the norm, for sound financial and technical reasons. With variety comes the need for open unencumbered standards for data exchange and service interoperability. You can address the theme from any angle you like--for example, you might talk about migrating away from commercial software such as Microsoft Windows, or instead place your emphasis on coexistence. Convention Conferences Perl Conference 7 The Python 11 Conference PHP Conference 3 Convention Tracks Apache XML Applications MySQL and PostgreSQL Ruby --Guido van Rossum (home page: http://www.python.org/~guido/)

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Re: A couple of questions on Pyrex
by Greg Ewing 12 Feb '03

12 Feb '03

> numbuf =3D data[2:30:4][1] > > in order to get a copy (in a new memory location) of the memory buffer = in > the selected slice to work with it. Would that be interesting to > implement?. It's an interesting idea, but I think it's getting somewhat beyond the scope of Pyrex. I don't think I'll be trying to implement anything like that in the foreseeable future. The Pyrex compiler is complicated enough already, and I don't want to add anything more that isn't really necessary. > Is (or will be) there any way in Pyrex to automagically create diferent > flavors of this function to deal with different datatypes? Same here, and even more so -- I'm *definitely* not going to re-implement C++ templates! :-) Greg Ewing, Computer Science Dept, +-------------------------------------= -+ University of Canterbury,=09 | A citizen of NewZealandCorp, a=09 | Christchurch, New Zealand=09 | wholly-owned subsidiary of USA Inc. | greg(a)cosc.canterbury.ac.nz=09 +--------------------------------------+ ------------------------------------------------------- --=20 Francesc Alted

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Re: A couple of questions on Pyrex
by Greg Ewing 12 Feb '03

12 Feb '03

> numbuf =3D data[2:30:4][1] > > in order to get a copy (in a new memory location) of the memory buffer = in > the selected slice to work with it. Would that be interesting to > implement?. It's an interesting idea, but I think it's getting somewhat beyond the scope of Pyrex. I don't think I'll be trying to implement anything like that in the foreseeable future. The Pyrex compiler is complicated enough already, and I don't want to add anything more that isn't really necessary. > Is (or will be) there any way in Pyrex to automagically create diferent > flavors of this function to deal with different datatypes? Same here, and even more so -- I'm *definitely* not going to re-implement C++ templates! :-) Greg Ewing, Computer Science Dept, +-------------------------------------= -+ University of Canterbury,=09 | A citizen of NewZealandCorp, a=09 | Christchurch, New Zealand=09 | wholly-owned subsidiary of USA Inc. | greg(a)cosc.canterbury.ac.nz=09 +--------------------------------------+ ------------------------------------------------------- --=20 Francesc Alted

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Interesting Psyco/Numeric/Numarray comparison
by Tim Hochberg 12 Feb '03

12 Feb '03

I was inspired by Armin's latest Psyco version to try and see how well one could do with NumPy/NumArray implemented in Psycotic Python. I wrote a bare bones, pure Python, Numeric array class loosely based on Jnumeric (which in turn was loosely based on Numeric). The buffer is just Python's array.array. At the moment, all that one can do to the arrays is add and index them and the code is still a bit of a mess. I plan to clean things up over the next week in my copius free time <0.999 wink> and at that point it should be easy add the remaining operations. I benchmarked this code, which I'm calling Psymeric for the moment, against NumPy and Numarray to see how it did. I used a variety of array sizes, but mostly relatively large arrays of shape (500,100) and of type Float64 and Int32 (mixed and with consistent types) as well as scalar values. Looking at the benchmark data one comes to three main conclusions: * For small arrays NumPy always wins. Both Numarray and Psymeric have much larger overhead. * For large, contiguouse arrays, Numarray is about twice as fast as either of the other two. * For large, noncontiguous arrays, Psymeric and NumPy are ~20% faster than Numarray The impressive thing is that Psymeric is generally slightly faster than NumPy when adding two arrays. It's slightly slower (~10%) when adding an array and a scalar although I suspect that could be fixed by some special casing a la Numarray. Adding two (500,100) arrays of type Float64 together results in the following timings: psymeric numpy numarray contiguous 0.0034 s 0.0038 s 0.0019 s stride-2 0.0020 s 0.0023 s 0.0033 s I'm not sure if this is important, but it is an impressive demonstration of Psyco! More later when I get the code a bit more cleaned up. -tim 0.002355 0.002355

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