# Questions tagged [vectorization]

Use this tag if your code contains vectorized operations - where functions operate on whole arrays in one go. If it doesn't, but you want it to, then you should make those changes (perhaps with help from elsewhere) before presenting code for review.

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### Vectorized 16-bit addition in Standard C

The idea is to add a given 16-bit number N to each element of an array of 16-bit integers of arbitrary length, taking advantage of 64-bit integer types and instructions to perform the additions 4 at a ...
1 vote
140 views

### Replace personal names and addresses with company ones

The problem: I am given a data frame. Somewhere in that dataframe there is 3*N number of columns that I need to modify based on a condition. The columns of interest look like this: names_1 address_1 ...
231 views

### Implementation of Iterative Closest Point in C++

Here, is my implementation of Iterative Closest Point algorithm in C++. The code is written using the Eigen library. I have tried to implement an efficient coding methodology best to my knowledge ...
1 vote
60 views

### Make unique id based on text data column with similarity scoring

I have the following dataframe: ...
59 views

### Three-dimensional DCT implementation for GPU computation in Matlab

This is a follow-up question for Three-dimensional DCT spatial frequency components illustration and Parallel 3D Discrete Cosine Transformation Implementation in Matlab. I am trying to perform three-...
1 vote
396 views

### Exponentially-weighted moving mean and standard deviation of an irregularly-spaced weighted time series

The following numpy/python function computes exponentially-weighted moving mean and standard deviation of an irregularly-spaced weighted time series. I want to make it faster by getting rid of the ...
45 views

### Tips to Finetuning to increase the GFLOPS of a SIMD kernel

Given an Image I with dimensions as {rows, columns}, for every pixel in the image, the following needs to be computed - ...
135 views

### Matlab vs C: Tensorproduct or Vec-trick (multiple times)

I am searching for a more efficient way to calculate the so called vec-trick used in Tensor algebra, see Wikipedia. Introduction: Suppose you have a matrix vector multiplication, where a matrix C ...
76 views

### Vectorizing a working custom similarity function further using numpy

I am new to python, and even more new to vectorization. I have attempted to vectorize a custom similarity function that should return a matrix of pairwise similarities between each row in an input ...
2k views

### My blit function for my own graphics library

Here is a blit function for a graphics library I made. I've built a small graphics library that uses an palette-indexed spritesheet to hold all of the game's sprites. The blit function copies parts of ...
1 vote
125 views

### Computing the angle between two vectors (vectorized) for small angles and with few copies

I am implementing a function that computes the angle between two vectors when given two n-dimensional arrays and an axis along which to operate. I want to do this with as few copies as possible, and ...
1 vote
52 views

### Correcting coordinates of an image with polynomial root in python

I want to optimize this for loop for correcting coordinates of an image, it takes too long which is not suited for my system. I have done some profiling, the numpy roots is taking most of the time (...
1 vote
123 views

### Faster Tridiagonal Matrix Multiplication

I have a function that I've been trying to make faster that computes $XA + B$, where $A \in \mathbb{R}^{n \times n}$ is a tridiagonal matrix, and $X, B \in \mathbb{R}^{m \times n}$. In the code, ...
114 views

### Snake from the viewpoint of the snake

I wrote a little game of snake that where you can see the field in which the snake moves fixed and you can also see the "viewpoint" of the snake, which is basically calculating the positions ...
50 views

### optimize binary classification method for speed

I have the following code for determining TP, TN, FP and FN values for binary classification given two sparse vectors as input (using the sparse library): ...
199 views

### Implement vectorization instead of nested loops on dataframe

I have a dataset ('sample_data.csv') of the form below: ...
91 views

### Can this numpy code be vectorized?

I've written the following function to produce n realizations of a CIR process for a given set of parameters: ...
369 views

### C# Generic high performance vectorized math operations

I'm writing a library which simplifies the usage of intrinsics in C#. It's a generic library which supports all numeric types. The goal of this library is to perform these operations at the highest ...
143 views

### Vectorized crosstabulation in Python for two arrays with two categories each

I have two Python lists, label and presence. I want to do cross-tabulation and get the count for each block out of four, such as ...
361 views

### N-Body Optimization

I've created a serial C++ code for gravitational N-Body calculation. Because I expect to have upwards of 8-71 sparse bodies (ie, where Barnes-Hut is not necessarily practical) and running for long ...
43 views

### Vectorize a function that, once per row, updates multiple rows in data.table

Requirements I have a table of the different diagnoses a patient has received, with the date the diagnosis was first recorded. It so happens that in medicine, diagnoses are recorded as codes from a ...
1 vote
51 views

### Vectorization of Mersenne Twister? [closed]

Ahoy friends. Right now i'm selling a huge amount of HDDs and usually i used DBAN or nwipe to perform this actions. Unfortunately the PRNG Mersenne Twister is quite slow, so i get a throughput of ...
354 views

### Efficiently shift elements right by one in an __mm256 vector [closed]

The code below correctly shifts v256f_stats by one and puts the results into v256f_x3. This is then used to get the delta ...
1 vote
158 views

### Custom Model intended to be used for Curve Fitting. Vectorization vs For Loop and jit numba capabilities

I am new to community and please pardon me if I didn't provide information as intended. This code is supposed to be creating a custom model which will be used with ...
557 views

### AVX Vectorized Multi-threaded Mandelbrot Renderer

I wrote a Mandelbrot renderer in C++ that uses AVX intrinsics to calculate 8 pixels per thread in parallel. It can compute 1080p frames with 256 max iterations in about 40 milliseconds on a 2 core 4 ...
172 views

311 views

### Optimizations of C Code - Bilateral Filter

I'm working on a nice approximation for the Bilateral Filter. I have a working code which runs pretty fast yet still I think much can be improved. The code (C Code,...
90 views

### Generic pixel class to seamlessly alpha-blend and convert between different pixel structure layouts

Does what it says in the title. I just finished this and wanted to share with someone. Looking for possible optimizations, bugs (most of it is tested to work) or any constructive criticism. ...
6k views

### Find first threshold crossing in numpy array

Given the following artificially generated data: ...
569 views

### Vectorizing a complex nested for loop in R (running models on different subsets of a data set, subsetting the data differently for each loop)

This is my first time posting so hopefully I manage to get my question across in a clear and concise manner. I'm not sure this is the right place but someone on StackOverflow suggested I ask here. I ...
66 views

### Determining whether a list of pathways and its genes are all included in another list

I am evaluating if a list of pathways and its genes has pathways included in another pathways. So the way I thought about it is to create a function that does just a single comparison. ...
1 vote
105 views

### Find the minimum value that data could have had before it was rounded

I have this function in R: ...
77 views

### 1D data classification

This R code separates the values in rData. They are classified according to the class in rClass. To do that, ...
8k views

### Compute a numerical derivative

Since I could not get numpy.gradient() to compute a derivative successfully, I wrote a script to compute it manually. Running the script below will output a plot of ... 290 views

### Merging bin-data via a bin count threshold

When performing a chi-squared test, one takes the square of the differences of the expected counts per bin and observed counts per bin, and divides these per-bin differences by the expected counts per ... 1 vote
87 views

### vectorize 2D gradient with spatially varying bins

The following code takes in some values ssh and solves the equations for the geostrophic motion (slide 8 here). The main part of the code is the computation of the ...
1 vote
942 views

### Normalise list of N dimensional numpy arrays

I have a list of N dimensional NumPy arrays. num_vecs = 10 dims = 2 vecs = np.random.normal(size=(num_vecs, dims)) I want to normalize them, so the magnitude/...
3k views

### Remove outliers from a point cloud

This function accepts a cloud of points, and returns those points that are within delta distance of the average (mean) position. ...