Author Archives: OmegaSharp

?: beyond the ternary operator (PHP surprise)

Posted on September 25, 2015 by OmegaSharp

Here is a famous ternary operator in C: condition ? A : B It can also be conveniently chained: condition1 ? A : condition2 ? B : condition3 ? C : D The evaluation of the conditions are in turns: condition1, condition2, … Continue reading →

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Populate and serialize text options (Java and C++)

Posted on July 27, 2015 by OmegaSharp

I find it convenient to have a unified text options, similar to those ini/rc files, with serializer/de-serializer for both Java and C++ and here is it. Sample text file: testmode=3 block_repeat=100 # floating point scaling_factor=0.9 # arrays c=1.0, -2.0, 1.0 … Continue reading →

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Lapack Java SGBTRF and SGBTRS

Posted on October 21, 2014 by OmegaSharp

A sample code in Java, as a memo of the correct indexing (row/col): import org.netlib.lapack.Sgbtrf; import org.netlib.lapack.Sgbtrs; /* Purpose: We want to use the LAPACK routines SGBTRF and SGBTRS to solve a banded linear system of the form A*x=b. Our … Continue reading →

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Overloading open() and fopen()

Posted on November 29, 2012 by OmegaSharp

One can overload fopen() and open() for debugging purpose, the example below traces each file opening operation: #include #include static FILE * (*next_fopen)(const char *path, const char *mode); FILE * fopen(const char *path, const char *mode) { char *msg; if … Continue reading →

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debug MPI programs with many slaves

Posted on September 13, 2012 by OmegaSharp

Although ddt is handy, in some cases one might want to do it the old fashioned way (e.g., debugging many nodes that exceeds the license limit, or, you do not have ddt). Instead opening 30 terminals and attach gdb to the … Continue reading →

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fgsl: single precision float version of gsl

Posted on February 25, 2012 by OmegaSharp

Many of GSL (GNU Scientific Library)’s routines are implemented in double only.  When one needs the additional speed and storage advantage, there wasn’t a quick way to go to float.  Here is a quick hack: cd gsl-1.15,  edit configure.ac, change … Continue reading →

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gcc build error: undefined _Unwind_Ptr

Posted on January 16, 2012 by OmegaSharp

I have tried on build both gcc-4.6.2 and gcc-4.6.1 and failed.  Here is the error: In file included from ../../.././libgcc/../gcc/unwind-dw2.c:35:0: ../../.././libgcc/../gcc/unwind-pe.h:101:1: error: unknown type name ‘_Unwind_Ptr’ Solution: rename the first unwind.h to another name and there should be another unwind.h … Continue reading →

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Passing class member function as argument

Posted on January 6, 2012 by OmegaSharp

Here is one example: Declaration: class CDifferentialFFT : public CDifferential {   …   double benchmark(void (CDifferential::*) (float*, float*, int), float* p, float* pz);   … } Implementation: double CDifferentialFFT::benchmark(void (CDifferential::*func) (float*, float*, int), float* p, float* pz) {   … … Continue reading →

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calloc for C++?

Posted on October 12, 2011 by OmegaSharp

It’s recommended to use: double * data = new double[mysize]; in C++ rather than the C-way: double * data = (double *)malloc(sizeof(double)*mysize); How about the one corresponds to calloc( ) ? Short memo here: double * data = new double[mysize](); … Continue reading →

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Install Stereo for 2007 Dodge Grand Caravan

Posted on October 2, 2011 by OmegaSharp

Recently I installed a new stereo for my 2007 Dodge Grand Caravan (the OEM one did not have MP3 capability and could not read from USB) and would like to document the steps for sharing. (Standard no-warranty disclaimer applies here — the … Continue reading →

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