Tag Archive: programming

Sep 12

BLAS and LAPACK

Back when I was new to the world of HPC, I was often confused as to what the distinction was between BLAS and LAPACK.  With the wealth of available memory model variants (shared, distributed), vendor implementations, and subroutine naming conventions, the amount of acronyms can get out of hand quickly.  The following is a little …

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Jul 22

Euclidean Algorithm

The Euclidean Algorithm recursively calculates the greatest common divisor (GCD) of two integers.  It works because GCD(a,b) = GCD(a mod b, b) = GCD(b, a mod b).  Each step of the algorithm reduces the size of the numbers by about a factor of 2.  The total number of steps required is roughly log(a*b).  It is …

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Jul 20

Calculating Fibonacci Numbers

The following C++ code calculates the Nth number in the Fibonacci sequence.  The first routine recursively calculates F_n, however it is very inefficient and takes an unrealistic amount of time to calculate even moderately high values for F_n (say 100).  The second routine generates the sequence sequentially on the fly up to F_n, and is …

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Jul 11

References and Pointers (C++)

Inspired by C++ Primer, Fifth Edition A reference refers to (is another name for) another object. Any operation on the reference actually operates on the object to which the reference is bounded. A pointer is an object itself (unlike a reference) and “points to” another object. Pointers can have four states: 1) It can point …

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Jun 28

Linear Regression in C++

The following is the gradient descent algorithm implemented for linear regression using C++ and the Eigen library:

Jun 28

Logistic Regression in C++

After taking Andrew Ng’s Machine Learning course, I decided to implement some of the algorithms in C++.  The following codes utilize the Eigen template library for linear algebra.  Also, I’m no master in C++, therefore take these codes with a grain of salt! In the course itself, a matlab optimization solver (fminunc) is used in …

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