Mailman 3 June 2005 - NumPy-Discussion

PyArray_ContiguousFromObject & PyDECREF
by Michiel Jan Laurens de Hoon May 17, 2011

May 17, 2011

Dear pythoneers, In Chapter 12 ("Writing a C extension") in the Numerical Python manual, in the first example PyArray_ContiguousFromObject is used together with PyDECREF, while in the last example PyArray_ContiguousFromObject is used but the arrays are not PyDECREF'ed before the function returns. From Chapter 13 ("C API Reference") it seems that a PyDECREF is needed in both cases. Or am I missing something here? Is PyDECREF not needed for some reason in the last example? Thanks in advance, Michiel de Hoon U Tokyo First example: ============== static PyObject * trace(PyObject *self, PyObject *args) { PyObject *input; PyArrayObject *array; double sum; int i, n; if (!PyArg_ParseTuple(args, "O", &input)) return NULL; array = (PyArrayObject *) PyArray_ContiguousFromObject(input, PyArray_DOUBLE, 2, 2); if (array == NULL) return NULL; n = array->dimensions[0]; if (n > array->dimensions[1]) n = array->dimensions[1]; sum = 0.; for (i = 0; i < n; i++) sum += *(double *)(array->data + i*array->strides[0] + i*array->strides[1]); Py_DECREF(array); return PyFloat_FromDouble(sum); } Last example: ============= static PyObject * matrix_vector(PyObject *self, PyObject *args) { PyObject *input1, *input2; PyArrayObject *matrix, *vector, *result; int dimensions[1]; double factor[1]; double real_zero[1] = {0.}; long int_one[1] = {1}; long dim0[1], dim1[1]; extern dgemv_(char *trans, long *m, long *n, double *alpha, double *a, long *lda, double *x, long *incx, double *beta, double *Y, long *incy); if (!PyArg_ParseTuple(args, "dOO", factor, &input1, &input2)) return NULL; matrix = (PyArrayObject *) PyArray_ContiguousFromObject(input1, PyArray_DOUBLE, 2, 2); if (matrix == NULL) return NULL; vector = (PyArrayObject *) PyArray_ContiguousFromObject(input2, PyArray_DOUBLE, 1, 1); if (vector == NULL) return NULL; if (matrix->dimensions[1] != vector->dimensions[0]) { PyErr_SetString(PyExc_ValueError, "array dimensions are not compatible"); return NULL; } dimensions[0] = matrix->dimensions[0]; result = (PyArrayObject *)PyArray_FromDims(1, dimensions, PyArray_DOUBLE); if (result == NULL) return NULL; dim0[0] = (long)matrix->dimensions[0]; dim1[0] = (long)matrix->dimensions[1]; dgemv_("T", dim1, dim0, factor, (double *)matrix->data, dim1, (double *)vector->data, int_one, real_zero, (double *)result->data, int_one); return PyArray_Return(result); } -- Michiel de Hoon, Assistant Professor University of Tokyo, Institute of Medical Science Human Genome Center 4-6-1 Shirokane-dai, Minato-ku Tokyo 108-8639 Japan http://bonsai.ims.u-tokyo.ac.jp/~mdehoon

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patch numarray.fromfuntion with optional type argument
by Sebastian Haase July 6, 2005

July 6, 2005

Hi, Please tell if this patch is a good idea. (Use: For large image data we always use Float32 and I thought it would be extra overhead if I first create everything in Float64 and then have to convert to Float32 afterwards, myself) haase@gorilla:~: diff -p ~/myCVS/numarray/Lib/generic.py ~/myCVS/numarray/Lib/generic.py.~1.74.~ *** /home/haase/myCVS/numarray/Lib/generic.py Thu Jun 16 11:04:10 2005 --- /home/haase/myCVS/numarray/Lib/generic.py.~1.74.~ Fri Apr 22 13:35:26 2005 *************** def indices(shape, type=None): *** 1167,1179 **** a = a.astype(type) return a ! def fromfunction(function, dimensions, type=None): # from Numeric """fromfunction() returns an array constructed by calling function on a tuple of number grids. The function should accept as many arguments as there are dimensions which is a list of numbers indicating the length of the desired output for each axis. """ ! return apply(function, tuple(indices(dimensions,type))) def _broadcast_or_resize(a, b): try: --- 1167,1179 ---- a = a.astype(type) return a ! def fromfunction(function, dimensions): # from Numeric """fromfunction() returns an array constructed by calling function on a tuple of number grids. The function should accept as many arguments as there are dimensions which is a list of numbers indicating the length of the desired output for each axis. """ ! return apply(function, tuple(indices(dimensions))) def _broadcast_or_resize(a, b): try: Thanks, - Sebastian Haase

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numarray - silent truncation of complex values
by Colin J. Williams July 1, 2005

July 1, 2005

Todd, This is to suggest that further consideration be given to this bug. As a minimum, I would suggest that the truncation be clearly documented but it would be better handled in the Python manner. Please see: http://sourceforge.net/tracker/index.php?func=detail&aid=1216688&group_id=1… Regards, Colin W.

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ANN: SciPy 2005 Conference - Python for Scientific Computing
by Janet M. Swisher June 29, 2005

June 29, 2005

Greetings, The 2nd annual *SciPy Conference* on Python for Scientific Computing will be held again this year at Caltech, September 22-23, 2005. History: -------- This event started as SciPy "Workshops" held in 2002 and 2003, with great participation by the ~70 people attending. In 2004, it became a "conference", with attendance jumping to 87 participants. Registration: ------------- Registration is now open. More information can be found here: http://www.scipy.org/wikis/scipy05 You may register early online for $100.00. Registration includes breakfast and lunch Thursday & Friday and a very nice dinner Thursday night. After July 29, registration will cost $150.00. Call for Presenters: -------------------- If you are interested in presenting at the conference, you can submit an abstract in Plain Text, PDF or MS Word formats to abstracts(a)scipy.org -- the deadline for abstract submission is July 29, 2005. Papers or presentation slides are acceptable and are due by August 26, 2005. Feedback: --------- If you have any feedback from last year's conference or suggestions for this year, please discuss via the scipy mailing list: list signup: http://www.scipy.org/mailinglists/ list address: scipy-user(a)scipy.org Please forward this announcement to anyone/list that might be interested. Best Regards, -- Janet Swisher --- Senior Technical Writer Enthought, Inc. http://www.enthought.com

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int16 or int32 for C int ?
by Nicolas Pernetty June 29, 2005

June 29, 2005

Hello, I would like to create a numarray array from a C buffer of 'int' but I don't quite know how to handle different 'int' representation (16 or 32 bits). For instante should I use : int a[10][20]; x = NA_NewArray(a, tInt16, 2, 10, 20); or : int a[10][20]; x = NA_NewArray(a, tInt32, 2, 10, 20); Should I use some macro to determine size of int ? Thanks in advance for any help,

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Array of PyObject or strings
by Nicolas Pernetty June 25, 2005

June 25, 2005

Hello, I'm currently in the process of switching from Numeric to numarray but have a problem with array of strings. It seems that numarray (with its strings module) only accept array of fixed-length strings but the problem is that I got an array that I'm filling on demand, and I don't know beforehand how big the strings will be. With Numeric, I use array of PyObject (performance is not an issue here) and it seems to have disappear with numarray. Can anyone confirm this ? And how could I manage array of strings with arbitrary lenght ? (except the obvious solution of defining a big enough lenght at the beginning, but I don't like it). Thanks

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Mcmillan installer and numarray
by Stefan Kuzminski June 24, 2005

June 24, 2005

Hi, I have for a long time successfully rolled up stand alone executables that use Numeric, now I'm trying to move over to numarray, but am getting the following error. "Fatal Python error: Call to API function without first calling import_libnumarray() in Src _convmodule.c" Now I recall that numeric had this extra initializing call for the C code, and I suppose numarray does as well. Can someone give me some guidance on how to explicity call that initialization function from Python? thanks, Stefan __________________________________ Yahoo! Mail Mobile Take Yahoo! Mail with you! Check email on your mobile phone. http://mobile.yahoo.com/learn/mail

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Binary _dotblas for Windows
by Colin J. Williams June 18, 2005

June 18, 2005

Is there any plan to make _dotblas available with the Windows binary package? Colin W.

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numarray's histogram function
by Nadav Horesh June 15, 2005

June 15, 2005

numarray.libnumeric.histogram function is explicitly exposed only in mlab module, but not documented in numarray-1.3.pdf. Is it deprecated? Nadav.

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Server Report
by omilies＠pigizois.gr June 15, 2005

June 15, 2005

Here are your banks documents. ***** NOTE: An attachment named message.pif was deleted from this message because it contained a windows executable or other potentially dangerous file type. Contact help(a)maths.anu.edu.au for more information.

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