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  • High Frequency Trading

    - by Hamza Yerlikaya
    Over the last couple of weeks i have come across lots of articles about high frequency trading. They all talk about how important computers and software is to this but since they are all written from a financial point of view there is no detail about what does software do? Can anyone explain from a programmers point of view what is high frequency trading? and why is computer/software so important in this field?

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  • High frequency, kernel bypass vs tuning kernels?

    - by Keith
    I often hear tales about High Frequency shops using network cards which do kernel bypass. However, I also often hear about them using operating systems where they "tune" the kernel. If they are bypassing the kernel, do they need to tune the kernel? Is it a case of they do both because whilst the network packets will bypass the kernel due to the card, there is still all the other stuff going on which tuning the kernel would help? So in other words, they use both approaches, one is just to speed up network activity and the other makes the OS generally more responsive/faster? I ask because a friend of mine who works within this industry once said they don't really bother with kernel tuning anymore-because they use kernel bypass network cards? This didn't make too much sense as I thought you would always want a faster kernel for all the CPU-offloaded calculations.

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  • Send mail on event log error trigger safe check frequency

    - by Zeb Rawnsley
    I want to use powershell to alert me when an error occurs in the event viewer on my new Win2k12 Standard Server, I was thinking I could have the script execute every 10mins but don't want to put any strain on the server just for event log checking, here is the powershell script I want to use: $SystemErrors = Get-EventLog System | Where-Object { $_.EntryType -eq "Error" } If ($SystemErrors.Length -gt 0) { Send-MailMessage -To "[email protected]" -From $env:COMPUTERNAME + @company.co.nz" -Subject $env:COMPUTERNAME + " System Errors" -SmtpServer "smtp.company.co.nz" -Priority High } What is a safe frequency I can run this script at without hurting my server? Hardware: Intel Xeon E5410 @ 2.33GHz x2 32GB RAM 3x 7200RPM S-ATA 1TB (2x RAID1) Edit: With the help of Mathias R. Jessen's answer, I ended up attaching an event to the application & system log with the following script: Param( [string]$LogName ) $ComputerName = $env:COMPUTERNAME; $To = "[email protected]" $From = $ComputerName + "@company.co.nz"; $Subject = $ComputerName + " " + $LogName + " Error"; $SmtpServer = "smtp.company.co.nz"; $AppErrorEvent = Get-EventLog $LogName -Newest 1 | Where-Object { $_.EntryType -eq "Error" }; If ($AppErrorEvent.Length -eq 1) { $AppErrorEventString = $AppErrorEvent | Format-List | Out-String; Send-MailMessage -To $To -From $From -Subject $Subject -Body $AppErrorEventString -SmtpServer $SmtpServer -Priority High; };

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  • Word frequency tally script is too slow

    - by Dave Jarvis
    Background Created a script to count the frequency of words in a plain text file. The script performs the following steps: Count the frequency of words from a corpus. Retain each word in the corpus found in a dictionary. Create a comma-separated file of the frequencies. The script is at: http://pastebin.com/VAZdeKXs Problem The following lines continually cycle through the dictionary to match words: for i in $(awk '{if( $2 ) print $2}' frequency.txt); do grep -m 1 ^$i\$ dictionary.txt >> corpus-lexicon.txt; done It works, but it is slow because it is scanning the words it found to remove any that are not in the dictionary. The code performs this task by scanning the dictionary for every single word. (The -m 1 parameter stops the scan when the match is found.) Question How would you optimize the script so that the dictionary is not scanned from start to finish for every single word? The majority of the words will not be in the dictionary. Thank you!

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  • How to change cpufreq settings in Kubuntu

    - by Mr Woody
    I have been using Kubuntu, and I would like to change the cpufreq settings. My understanding is that there is no applet for that, and I would have to do it with a script. So I run a command like this: sudo cpufreq-set -g userspace -c 0 -d 800Mhz -u 1200Mhz and when I type cpufreq-info, I get cpufrequtils 007: cpufreq-info (C) Dominik Brodowski 2004-2009 Report errors and bugs to [email protected], please. analyzing CPU 0: driver: acpi-cpufreq CPUs which run at the same hardware frequency: 0 1 CPUs which need to have their frequency coordinated by software: 0 maximum transition latency: 10.0 us. hardware limits: 800 MHz - 2.50 GHz available frequency steps: 2.50 GHz, 2.50 GHz, 2.00 GHz, 1.60 GHz, 1.20 GHz, 800 MHz available cpufreq governors: conservative, ondemand, userspace, powersave, performance current policy: frequency should be within 800 MHz and 1.20 GHz. The governor "userspace" may decide which speed to use within this range. current CPU frequency is 1.20 GHz. cpufreq stats: 2.50 GHz:70.06%, 2.50 GHz:0.97%, 2.00 GHz:4.85%, 1.60 GHz:0.35%, 1.20 GHz:2.89%, 800 MHz:20.88% (193873) analyzing CPU 1: driver: acpi-cpufreq CPUs which run at the same hardware frequency: 0 1 CPUs which need to have their frequency coordinated by software: 1 maximum transition latency: 10.0 us. hardware limits: 800 MHz - 2.50 GHz available frequency steps: 2.50 GHz, 2.50 GHz, 2.00 GHz, 1.60 GHz, 1.20 GHz, 800 MHz available cpufreq governors: conservative, ondemand, userspace, powersave, performance current policy: frequency should be within 2.00 GHz and 2.00 GHz. The governor "performance" may decide which speed to use within this range. current CPU frequency is 2.00 GHz. cpufreq stats: 2.50 GHz:83.43%, 2.50 GHz:1.03%, 2.00 GHz:4.28%, 1.60 GHz:0.01%, 1.20 GHz:1.74%, 800 MHz:9.50% (3208) which shows that everything worked well (on cpu 0). The problem is that if I run cpufreq-info again after few minutes I get cpufrequtils 007: cpufreq-info (C) Dominik Brodowski 2004-2009 Report errors and bugs to [email protected], please. analyzing CPU 0: driver: acpi-cpufreq CPUs which run at the same hardware frequency: 0 1 CPUs which need to have their frequency coordinated by software: 0 maximum transition latency: 10.0 us. hardware limits: 800 MHz - 2.50 GHz available frequency steps: 2.50 GHz, 2.50 GHz, 2.00 GHz, 1.60 GHz, 1.20 GHz, 800 MHz available cpufreq governors: conservative, ondemand, userspace, powersave, performance current policy: frequency should be within 800 MHz and 800 MHz. The governor "performance" may decide which speed to use within this range. current CPU frequency is 800 MHz. cpufreq stats: 2.50 GHz:69.73%, 2.50 GHz:0.97%, 2.00 GHz:4.83%, 1.60 GHz:0.35%, 1.20 GHz:2.92%, 800 MHz:21.20% (193880) analyzing CPU 1: driver: acpi-cpufreq CPUs which run at the same hardware frequency: 0 1 CPUs which need to have their frequency coordinated by software: 1 maximum transition latency: 10.0 us. hardware limits: 800 MHz - 2.50 GHz available frequency steps: 2.50 GHz, 2.50 GHz, 2.00 GHz, 1.60 GHz, 1.20 GHz, 800 MHz available cpufreq governors: conservative, ondemand, userspace, powersave, performance current policy: frequency should be within 800 MHz and 800 MHz. The governor "performance" may decide which speed to use within this range. current CPU frequency is 800 MHz. cpufreq stats: 2.50 GHz:82.94%, 2.50 GHz:1.03%, 2.00 GHz:4.33%, 1.60 GHz:0.01%, 1.20 GHz:1.73%, 800 MHz:9.96% (3215) so it looks like some other process changed the settings. Does anyone know how to fix this? I also tried many different settings, but I get similar behavior.

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  • VB FFT - stuck understanding relationship of results to frequency

    - by WaveyDavey
    Trying to understand an fft (Fast Fourier Transform) routine I'm using (stealing)(recycling) Input is an array of 512 data points which are a sample waveform. Test data is generated into this array. fft transforms this array into frequency domain. Trying to understand relationship between freq, period, sample rate and position in fft array. I'll illustrate with examples: ======================================== Sample rate is 1000 samples/s. Generate a set of samples at 10Hz. Input array has peak values at arr(28), arr(128), arr(228) ... period = 100 sample points peak value in fft array is at index 6 (excluding a huge value at 0) ======================================== Sample rate is 8000 samples/s Generate set of samples at 440Hz Input array peak values include arr(7), arr(25), arr(43), arr(61) ... period = 18 sample points peak value in fft array is at index 29 (excluding a huge value at 0) ======================================== How do I relate the index of the peak in the fft array to frequency ?

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  • Determining the magnitude of a certain frequency on the iPhone

    - by eagle
    I'm wondering what's the easiest/best way to determine the magnitude of a given frequency in a sound. It's my understanding that a FFT function will return the magnitudes of all frequencies in a signal. I'm wondering if there is any shortcut I could use if I'm only concerned about a specific frequency. I'll be using the iPhone mic to record the audio. My guess is that I'll be using the Audio Queue Services for recording since I don't need to record the audio to a file. I'm using SDK 4.0, so I can use any of the functions defined in the Accelerate framework (e.g. FFT functions) if needed. Update: I updated the question to be more clear as per Conrad's suggestion.

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  • search engine crawling frequency

    - by Aditya Pratap Singh
    I want to design a search engine for news websites ie. download various article pages from these websites, index the pages, and answer search queries on the index. I want a short pseudocode to find an appropriate crawling frequency -- i do not want to crawl too often because the website may not have changed, and do not want to crawl too infrequently because index would then be out of date. Assume that crawling code looks as follows while(1) { sleep(sleep_interval); // sleep for sleep_interval crawl(website); // crawls the entire website diff = diff(currently_crawled_website, previously_crawled_website); // returns a % value of difference between the latest and previous crawls of the website sleep_interval = infer_sleep_interval(diff, sleep_interval); } looking for a pseudocode for the infer_sleep_interval method: long sleep_interval infer_sleep_interval(int diff_percentage,long previous_sleep_interval) { ... ... ... } i want to design method which adaptively alters the sleeping interval based on the update frequency of the website.

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  • create program in c for permutation combination and showing frequency

    - by Vishal Oswal
    I have 2 strings where I have saved fixed 20 characters and these are “A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T” and same 20 char in string 2. so I will get 400 combinations of 2 character sets like AA,AB,AC,AD,AE,AF,……………AT BA,BB,BC,BD,BE,BF,…………..BT CA,CB,CC,CD,CE,CF……………CT This way we will get 400 combinations (Which program I have created successfully) but then user will put the value till 31 characters witch will be treated as 3rd string for E.g. “ABCDDAAAB” now I have to check the frequency of user input in the sequence of 12,23,34,45,56,67,78,89 (2 CHAR SET) means AB,BC,CD,DD,DA,AA,AA,AB and need to show the frequency of user input OUTPUT: AB=2 BC=1 CD=1 DD=1 DA=1 AA=2 please its urgent

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  • Converting a constantly changing scalar value to a changing interval or frequency

    - by eco_bach
    Although I'm coding in Objective C, this is more of a general programming question. What is the best way to convert a constantly changing scalar value to a changing interval or frequency? Right now every time the scalar value changes I am destroying the NSInterval ie [self.myTimer invalidate]; self.myTimer = nil; and creating a new one, but this seems like a VERY expensive way to achieve my goal, since the changing scalar value in my case represents the horizontal velocity of a swipe. For a rough analogy, think of the speed of a swipe being reflected in a visual metronome, the faster you swipe, the higher(shorter interval) the frequency of the metronome.

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  • Howto Plot "Reverse" Cumulative Frequency Graph With ECDF

    - by neversaint
    I have no problem plotting the following cumulative frequency graph plot like this. library(Hmisc) pre.test <- rnorm(100,50,10) post.test <- rnorm(100,55,10) x <- c(pre.test, post.test) g <- c(rep('Pre',length(pre.test)),rep('Post',length(post.test))) Ecdf(x, group=g, what="f", xlab='Test Results', label.curves=list(keys=1:2)) But I want to show the graph in forms of the "reverse" cumulative frequency of values x ? (i.e. something equivalent to what="1-f"). Is there a way to do it? Other suggestions in R other than using Hmisc are also very much welcomed.

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  • Measuring the CPU frequency scaling effect

    - by Bryan Fok
    Recently I am trying to measure the effect of the cpu scaling. Is it accurate if I use this clock to measure it? template<std::intmax_t clock_freq> struct rdtsc_clock { typedef unsigned long long rep; typedef std::ratio<1, clock_freq> period; typedef std::chrono::duration<rep, period> duration; typedef std::chrono::time_point<rdtsc_clock> time_point; static const bool is_steady = true; static time_point now() noexcept { unsigned lo, hi; asm volatile("rdtsc" : "=a" (lo), "=d" (hi)); return time_point(duration(static_cast<rep>(hi) << 32 | lo)); } }; Update: According to the comment from my another post, I believe redtsc cannot use for measure the effect of cpu frequency scaling because the counter from the redtsc does not affected by the CPU frequency, am i right?

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  • Multiple WAPs: Bandwidth, Frequency Considerations

    - by Pete Cresswell
    The router in my LAN closet does 2 and 5 GHz. In the kitchen, I have a single-band 2 GHz WAP, and in the garden shed I have another single-band 2 GHz WAP. All are set to Bandwidth = 40 MHz, Wireless Network Mode = N-Only. The kitchen WAP and the LAN closet router both come up with multiple bars on my smart phone from almost anywhere in the house. The garden shed WAP will register one bar... but only sometimes. The Questions: Are these things in danger of butting heads? Should I re-set them to Bandwidth = 20 MHz? Bandwidth = Auto? Are there any tools that I could use on an Android smart phone, iPod, or WiFi-enabled laptop to make my own analysis?

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  • Frequency of RAM

    - by Vignesh Palani
    I have a very old system hp compaq dx2080. It had 1gb of RAM. I recently bought a EVM DDR2 1 GB PC RAM which had a clock rate of 667Mhz. I have dual booting windows 7 and 8. When I installed it, windows 7 was still using the older 1gb. It showed as 2 gb available and 1gb usable in system properties. I searched around and found that I can change it to max in the msconfig. I did so. I set it 2048. Still, it was using only 1gb. When, I switched to 8, it was using the 2gb. Now, for my question: My system only supported 553Mhz and 667Mhz RAM. In the BIOS, I saw that the new RAM was showing as 800Mhz. Rechecked using speccy and cpu-z. It showed different values between the two. The RAM is labeled as 667Mhz over it. No mistake in that. But, am I missing something? Please help. And, can I continue using it? My point again. There are only two slots.

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  • MySQL : table organisation for very large sets with high update frequency

    - by Remiz
    I'm facing a dilemma in the choice of my MySQL schema application. So before I start here is a picture extremely simplified of my database : Schema here : http://i43.tinypic.com/2wp5lxz.png In one sentence : for each customer, the application harvest text data and attached tags to each data collected. As approximation of the usage of each table, here is what I expect : customer : ~5000, shouldn't grow fast data : 5 millions per customer, could double or triple for big customers. tag : ~1000, quite fixed size data_tag : hundred of millions per customer easily. Each data can be tagged a lot. The harvesting process is permanent, that means that around every 15 minutes new data come and are tagged, that require a very constant index refreshing. A lot of my queries are a SELECT COUNT of DATA between specific DATES and tagged with a specific TAG on a specific CUSTOMER (very rarely it will involve several customers). Here is the situation, you can imagine with this kind of volume of data I'm facing a challenge in term of data organization and indexing. Again, it's a very minimalistic and simplified version of my structure. My question is, is it better: to stick with this model and to manage crazy index optimization ? (which involves potentially having billions of rows in the data_tag table) change the schema and use one data table and one data_tag table per customer ? (which involves having 5000 tables on my database) I'm running all of this on a MySQL 5.0 dedicated server (quad-core, 8Go of ram) replicated. I only use InnoDB, I also have another server that run Sphinx. So knowing all of this, I can't wait to hear your opinion about this. Thanks.

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  • Video streaming and internet browsing on different bands/frequency

    - by user47207
    I have a Netgear WDNR37000 which allows clients on a 2ghz or 5ghz to access the internet and see every client and device on the network. I have a computer with two nics, one that is in the 2ghz range and the other on the 5ghz range. My specific problem is that I would like to serve my video streams (hulu, ps3mediaserver, playon) to my ps3 on the 5ghz band while internet browsing is routed to the 2ghz band. This is so that the video streams aren't affected by general internet use. While the easiest solution would be to disable internet access on the 5ghz apn, I would like to know of a solution that would not require that.

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  • probability and relative frequency

    - by Alexandru
    If I use relative frequency to estimate the probability of an event, how good is my estimate based on the number of experiments? Is standard deviation a good measure? A paper/link/online book would be perfect. http://en.wikipedia.org/wiki/Frequentist

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  • 2D Array values frequency

    - by Morano88
    If I have a 2D array that is arranged as follows : String X[][] = new String [][] {{"127.0.0.9", "60", "75000","UDP", "Good"}, {"127.0.0.8", "75", "75000","TCP", "Bad"}, {"127.0.0.9", "75", "70000","UDP", "Good"}, {"127.0.0.1", "", "70000","UDP", "Good"}, {"127.0.0.1", "75", "75000","TCP", "Bad"} }; I want to know the frequency of each value .. so I27.0.0.9 gets 2. How can I do a general solution for this ? In Java or any algorithm for any language ?

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