Posts tagged as «C#»

My recent side project: sChord.com.

From the Equation OCR front line…

Problem:

Splitting up handwritten calculations into single lines.

Algorithm description:

First map all the strokes on the y-axis. Then travel along the axis and record the the ink density (number of strokes underneath). Remember local maximums. If the density falls below a certain percentage (tolerance) of a last local maximum – insert a break line.

C# code:

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…you can look but you better not touch

Recently I’ve started working on a new project with my friend, so development of Falasol will be slower for a while. But fear not – I’m not going to give up on that. Falasol is my long term plan and what you can see so far is just a little part of it. I expect to get back to it next year. Meanwhile I’ll be occasionally posting stories from EqOCR development. You probably guessed that it will have something to do with equations & math – that is correct.

It was back at school when I discovered the charm of equations

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As promised last week I’m going to compare three methods of optimizing 2 ^ x calculation:

• Cache table – described in my previous post
• Polynomial approximation – suggested by Gregory, implemented here celt_exp2(…) and described here
• Compact IEEE-754 – 3 lines of code(!) described here and here

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Signal processing often requires moving between logarithmic & linear domains. In audio area we can talk about Octaves (logarithmic representation) and Frequencies (linear representation). Octave -> Frequency conversion corresponds to transformation x = 2 ^ x.

Most programming languages provide support for such calculation, for example Pow(a, b) in C#.
Those functions however tend to be time consuming. We can take advantage of the fact that in our case a = const = 2 and optimize the calculation.
Let’s start with equation:

a ^ ( b + c ) = a ^ b * a ^ c

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