Mailman 3 November 2003 - NumPy-Discussion

PyArray_ContiguousFromObject & PyDECREF
by Michiel Jan Laurens de Hoon 16 May '11

16 May '11

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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PyMatrix: Announcement
by Colin J. Williams 09 Dec '03

09 Dec '03

PyMatrix is available for test and review. http://www3.sympatico.ca/cjw PyMatrix provides access to basic matrix arithmetic, using Python and numarray. Examples: A * B => the product of matrices A and B A.I => the inverse of matrix A A.EVectors => the eigenvectors of A A.var(0) => the variances of the columns of A (a.T*a).I * a.T*b => the solution (x) for a * x = b, where a is a matrix and b a column vector This package was developed on a Windows XP. I would appreciate comments, particularly with respect to usage on other systems. Colin W.

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R E S U M E
by E l e c t r i c i a n 29 Nov '03

29 Nov '03

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ANN: PyQwt-3.8
by Gerard Vermeulen 26 Nov '03

26 Nov '03

PyQwt-3.8 = FAST and EASY data plotting for Python and (Py)Qt. PyQwt is a set of Python bindings for the Qwt C++ class library which extends the Qt framework with widgets for scientific and engineering applications. It supports the use of PyQt, Qt, Qwt, the Numerical Python extensions (either Numeric, or numarray or both) and optionally SciPy in a GUI Python application or in an interactive Python session. The home page of PyQwt is http://pyqwt.sourceforge.net. Main changes in PyQwt-3.8: 1. PyQwt inherits from Qwt the new classes QwtPicker, QwtPlotPicker and QwtPlotZoomer. QwtPicker can make any widget react to events by event filtering. QwtPlotPicker is a QwtPicker taylored to the plot canvas. QwtPlotZoomer implements infinite deep zooming on the plot canvas. 2. PyQwt inherits from Qwt the support for Qt's rich text format in QwtPlot to display equations like E=mc<sup>2</sup>. Caveat: in principle, a truetype font with full unicode support is better to typeset equations. 3. Bug fixes to support event filtering code (see EventFilterDemo.py). 4. Conversion of a QImage to a Numeric array or numarray array. 5. Better support for cloning a plot into Grace from the command line interpreter friendly plot classes. 6. PyQwt-3.8 works with PyQt-3.8.1 downto -3.6 and Qt-3.2.3 downto -2.3.0. 7. License change: GPL with permission for dynamic linking to commercial, educational and non-commercial versions of Qt, PyQt and sip. In this case PyQwt becomes a free plug-in for a non-free program. Gerard Vermeulen

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PyMatrix: Announcement
by Colin J. Williams 25 Nov '03

25 Nov '03

In response to a number of requests, the PyMatrix package is now available for download as a zip file. Colin W. > PyMatrix is available for test and review. > http://www3.sympatico.ca/cjw > > PyMatrix provides access to basic matrix arithmetic, using Python and > numarray. > > Examples: > A * B => the product of matrices A and B > A.I => the inverse of matrix A > A.EVectors => the eigenvectors of A > A.var(0) => the variances of the columns of A > (a.T*a).I * a.T*b => the solution (x) for a * x = b, > where a is a matrix and b a column vector > > This package was developed on a Windows XP. I would appreciate > comments, particularly with respect to usage on other systems. > > Colin W. >

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how-to "put" RAM-based numarray into memmap
by Sebastian Haase 24 Nov '03

24 Nov '03

Hi, Suppose I have a 500MB-ram Computer and a 300MB ram-only (standard) numarray. Now I would like to "save" that onto harddrive (with a small header up front - which I know how to do as a memmap record) Can I somehow "append" a (standard) numarray to a memmap "as a memmap-slice" ? I obviously could create the corresponding memslice fresh and then assign the original data elementwise - but that would allocate extra (virtual) memory... Thanks, Sebastian Haase

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Community Poll: numarray default underflow handling == "ignore" ?
by Todd Miller 24 Nov '03

24 Nov '03

Someone recently suggested that we change the default for numarray underflow checking to "ignore". Please vote (+1, 0, -1): Todd -- Todd Miller Space Telescope Science Institute 3700 San Martin Drive Baltimore MD, 21030 (410) 338 - 4576

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by Hosting 23 Nov '03

23 Nov '03

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Re: [Numpy-discussion] Community Poll: numarray default underflow handling == "ignore" ?
by verveer＠embl.de 22 Nov '03

22 Nov '03

+1 for "ignore" Peter

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teacup.py crash
by Colin J. Williams 20 Nov '03

20 Nov '03

Running teacup.py, we get: Traceback (most recent call last): File "C:\Program Files\Python23\Lib\site-packages\numarray\teacup.py", line 1, in ? import numarray.libteacup ImportError: No module named libteacup There is no mention of teacup in numarray-0.6.pdf. Can this module be safely be deleted? Colin W

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NumPy-Discussion November 2003