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  • DSP - How are frequency amplitudes modified using DFT?

    - by Trap
    I'm trying to implement a DFT-based equalizer (not FFT) for the sole purpose of learning. To check if it works I took an audio signal, analyzed it and then resynthesized it again with no modifications made to the frequency spectrum. So far so good. Now I tried to silence some frequency bands, just by setting their amplitudes to zero before resynthesis, but definitely it's not the way to go. What I get is a rather distorted signal. I'm using the so-called 'standard way of calculating the DFT' which is by correlation. I first tried to modify the real part amplitudes only, then modifying both the real and imaginary part amplitudes. I also tried to convert the DFT output to polar notation, then modifying the magnitude and convert back to rectangular notation, but none of this is working. Can someone show me what I'm doing wrong? I tried to find info on this subject in the internet but couldn't find any. Thanks in advance.

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  • DSP - Problems using the inverse Fast Fourier Transform

    - by Trap
    I've been playing around a little with the Exocortex implementation of the FFT, but I'm having some problems. First, after calculating the inverse FFT of an unchanged frequency spectrum obtained by a previous forward FFT, one would expect to get the original signal back, but this is not the case. I had to figure out that I needed to scale the FFT output to about 1 / fftLength to get the amplitudes ok. Why is this? Second, whenever I modify the amplitudes of the frequency bins before calling the iFFT the signal gets distorted at low frequencies. However, this does not happen if I attenuate all the bins by the same factor. Let me put a very simplified example of the output buffer of a 4-sample FFT: // Bin 0 (DC) FFTOut[0] = 0.0000610351563 FFTOut[1] = 0.0 // Bin 1 FFTOut[2] = 0.000331878662 FFTOut[3] = 0.000629425049 // Central bin FFTOut[4] = -0.0000381469727 FFTOut[5] = 0.0 // Bin 3, this is a negative frequency bin. FFTOut[6] = 0.000331878662 FFTOut[7] = -0.000629425049 The output is composed of pairs of floats, each representing the real and imaginay parts of a single bin. So, bin 0 (array indexes 0, 1) would represent the real and imaginary parts of the DC frequency. As you can see, bins 1 and 3 both have the same values, (except for the sign of the Im part), so I guess these are the negative frequency values, and finally indexes (4, 5) would be the central frequency bin. To attenuate the frequency bin 1 this is what I do: // Attenuate the 'positive' bin FFTOut[2] *= 0.5; FFTOut[3] *= 0.5; // Attenuate its corresponding negative bin. FFTOut[6] *= 0.5; FFTOut[7] *= 0.5; For the actual tests I'm using a 1024-length FFT and I always provide all the samples so no 0-padding is needed. // Attenuate var halfSize = fftWindowLength / 2; float leftFreq = 0f; float rightFreq = 22050f; for( var c = 1; c < halfSize; c++ ) { var freq = c * (44100d / halfSize); // Calc. positive and negative frequency locations. var k = c * 2; var nk = (fftWindowLength - c) * 2; // This kind of attenuation corresponds to a high-pass filter. // The attenuation at the transition band is linearly applied, could // this be the cause of the distortion of low frequencies? var attn = (freq < leftFreq) ? 0 : (freq < rightFreq) ? ((freq - leftFreq) / (rightFreq - leftFreq)) : 1; mFFTOut[ k ] *= (float)attn; mFFTOut[ k + 1 ] *= (float)attn; mFFTOut[ nk ] *= (float)attn; mFFTOut[ nk + 1 ] *= (float)attn; } Obviously I'm doing something wrong but can't figure out what or where.

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  • DSP - Filtering frequencies using DFT

    - by Trap
    I'm trying to implement a DFT-based 8-band equalizer for the sole purpose of learning. To prove that my DFT implementation works I fed an audio signal, analyzed it and then resynthesized it again with no modifications made to the frequency spectrum. So far so good. I'm using the so-called 'standard way of calculating the DFT' which is by correlation. This method calculates the real and imaginary parts both N/2 + 1 samples in length. To attenuate a frequency I'm just doing: float atnFactor = 0.6; Re[k] *= atnFactor; Im[k] *= atnFactor; where 'k' is an index in the range 0 to N/2, but what I get after resynthesis is a slighty distorted signal, especially at low frequencies. The input signal sample rate is 44.1 khz and since I just want a 8-band equalizer I'm feeding the DFT 16 samples at a time so I have 8 frequency bins to play with. Can someone show me what I'm doing wrong? I tried to find info on this subject on the internet but couldn't find any. Thanks in advance.

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  • DSP - Filtering in the frequency domain via FFT

    - by Trap
    I've been playing around a little with the Exocortex implementation of the FFT, but I'm having some problems. Whenever I modify the amplitudes of the frequency bins before calling the iFFT the resulting signal contains some clicks and pops, especially when low frequencies are present in the signal (like drums or basses). However, this does not happen if I attenuate all the bins by the same factor. Let me put an example of the output buffer of a 4-sample FFT: // Bin 0 (DC) FFTOut[0] = 0.0000610351563 FFTOut[1] = 0.0 // Bin 1 FFTOut[2] = 0.000331878662 FFTOut[3] = 0.000629425049 // Bin 2 FFTOut[4] = -0.0000381469727 FFTOut[5] = 0.0 // Bin 3, this is the first and only negative frequency bin. FFTOut[6] = 0.000331878662 FFTOut[7] = -0.000629425049 The output is composed of pairs of floats, each representing the real and imaginay parts of a single bin. So, bin 0 (array indexes 0, 1) would represent the real and imaginary parts of the DC frequency. As you can see, bins 1 and 3 both have the same values, (except for the sign of the Im part), so I guess bin 3 is the first negative frequency, and finally indexes (4, 5) would be the last positive frequency bin. Then to attenuate the frequency bin 1 this is what I do: // Attenuate the 'positive' bin FFTOut[2] *= 0.5; FFTOut[3] *= 0.5; // Attenuate its corresponding negative bin. FFTOut[6] *= 0.5; FFTOut[7] *= 0.5; For the actual tests I'm using a 1024-length FFT and I always provide all the samples so no 0-padding is needed. // Attenuate var halfSize = fftWindowLength / 2; float leftFreq = 0f; float rightFreq = 22050f; for( var c = 1; c < halfSize; c++ ) { var freq = c * (44100d / halfSize); // Calc. positive and negative frequency indexes. var k = c * 2; var nk = (fftWindowLength - c) * 2; // This kind of attenuation corresponds to a high-pass filter. // The attenuation at the transition band is linearly applied, could // this be the cause of the distortion of low frequencies? var attn = (freq < leftFreq) ? 0 : (freq < rightFreq) ? ((freq - leftFreq) / (rightFreq - leftFreq)) : 1; // Attenuate positive and negative bins. mFFTOut[ k ] *= (float)attn; mFFTOut[ k + 1 ] *= (float)attn; mFFTOut[ nk ] *= (float)attn; mFFTOut[ nk + 1 ] *= (float)attn; } Obviously I'm doing something wrong but can't figure out what. I don't want to use the FFT output as a means to generate a set of FIR coefficients since I'm trying to implement a very basic dynamic equalizer. What's the correct way to filter in the frequency domain? what I'm missing? Thanks in advance.

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  • DSP - Filter sweep effect

    - by Trap
    I'm implementing a 'filter sweep' effect (I don't know if it's called like that). What I do is basically create a low-pass filter and make it 'move' along a certain frequency range. To calculate the filter cut-off frequency at a given moment I use a user-provided linear function, which yields values between 0 and 1. My first attempt was to directly map the values returned by the linear function to the range of frequencies, as in cf = freqRange * lf(x). Although it worked ok it looked as if the sweep ran much faster when moving through low frequencies and then slowed down during its way to the high frequency zone. I'm not sure why is this but I guess it's something to do with human hearing perceiving changes in frequency in a non-linear manner. My next attempt was to move the filter's cut-off frequency in a logarithmic way. It works much better now but I still feel that the filter doesn't move at a constant perceived speed through the range of frequencies. How should I divide the frequency space to obtain a constant perceived sweep speed? Thanks in advance.

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  • Are doubles faster than floats in c#?

    - by Trap
    I'm writing an application which reads large arrays of floats and performs some simple operations with them. I'm using floats because I thought it'd be faster than doubles, but after doing some research I've found that there's some confusion about this topic. Can anyone elaborate on this? Thanks.

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  • How much faster is C++ than C#?

    - by Trap
    Or is it now the other way around? From what I've heard there are some areas in which C# proves to be faster than C++, but I've never had the guts to test it by myself. Thought any of you could explain these differences in detail or point me to the right place for information on this.

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  • Is it possible to access a remote SWF without needing to download it?

    - by Trap
    We have a very large SWF hosted in a website which is just a repository of hundreds of movies/symbols. We load this SWF at the beginning with the Loader class but then the client will access a very few of them at that moment. Is it possible to tell the loader to download symbols only when they're needed? (as with applicationDomain.getDefinition(...)). Thanks in advance.

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  • performing simple stack overflow on Mac os 10.6

    - by REALFREE
    I'm trying to learn about stack base overflow and write a simple code to exploit stack. But somehow it doesn't work at all but showing only Abort trap on my machine (mac os leopard) I guess Mac os treats overflow differently, it won't allow me to overwrite memory through c code. for example, strcpy(buffer, input) // lets say char buffer[6] but input is 7 bytes on Linux machine, this code successfully overwrite next stack, but prevented on mac os (Abort trap) Anyone know how to perform a simple stack-base overflow on mac machine?

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  • performing simple buffer overflow on Mac os 10.6

    - by REALFREE
    I'm trying to learn about stack base overflow and write a simple code to exploit stack. But somehow it doesn't work at all but showing only Abort trap on my machine (mac os leopard) I guess Mac os treats overflow differently, it won't allow me to overwrite memory through c code. for example, strcpy(buffer, input) // lets say char buffer[6] but input is 7 bytes on Linux machine, this code successfully overwrite next stack, but prevented on mac os (Abort trap) Anyone know how to perform a simple stack-base overflow on mac machine?

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  • Java MouseListener

    - by ikurtz
    I have a bunch of JLabels and i would like to trap mouse click events. at the moment i am having to use: public void mouseClicked(MouseEvent arg0) { } public void mouseExited(MouseEvent arg0) { } public void mouseEntered(MouseEvent arg0) { } public void mousePressed(MouseEvent arg0) { } public void mouseReleased(MouseEvent arg0) { System.out.println("Welcome to Java Programming!"); } I was wondering if there is a tidier way of doing this instead of having a bunch of events I do not wish trap?

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  • hp smart array lock up code 0x15, what is that? (or where can I get a list of descriptions of HP smart array controller lock up codes)

    - by user47650
    Hi, I've had a couple of Dl180 6g boxes hung over the last week, each have a P410 smart array controller. upon reboot the server has indicated that a controller failure event occurred and the previous lock up code was 0x15 - the server rebooted without issue. However there was nothing in the IML log, but the ADU report provided the following; Trap Address High Or Post Results Lockup Reason Or Post Error RIS Updates Or Post Error Detail Firmware Version Trap Address Low 0x8087 0x0015 0x0000033e 0x015e 0xd65c any suggestions on what that code is, my google fu failed. And hp support have not responded with any detail as yet.

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  • Booby Traps and Locked-in Kids: An Interview with a Safecracker

    - by Jason Fitzpatrick
    While most of our articles focus on security of the digital sort, this interview with a professional safecracker is an interesting look the physical side of securing your goods. As part of their Interviews with People Who Have Interesting or Unusual Jobs series over at McSweeney’s, they interviewed Ken Doyle, a professional a locksmithing and safecracking veteran with 30 years of industry experience. The interview is both entertaining and an interesting read. One of the more unusual aspects of safecracking he highlights: Q: Do you ever look inside? A: I NEVER look. It’s none of my business. Involving yourself in people’s private affairs can lead to being subpoenaed in a lawsuit or criminal trial. Besides, I’d prefer not knowing about a client’s drug stash, personal porn, or belly button lint collection. When I’m done I gather my tools and walk to the truck to write my invoice. Sometimes I’m out of the room before they open it. I don’t want to be nearby if there is a booby trap. Q: Why would there be a booby trap? A: The safe owner intentionally uses trip mechanisms, explosives or tear gas devices to “deter” unauthorized entry into his safe. It’s pretty stupid because I have yet to see any signs warning a would-be culprit about the danger. HTG Explains: Why Linux Doesn’t Need Defragmenting How to Convert News Feeds to Ebooks with Calibre How To Customize Your Wallpaper with Google Image Searches, RSS Feeds, and More

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  • Comparing Dates in Oracle Business Rule Decision Tables

    - by James Taylor
    I have been working with decision tables for some time but have never had a scenario where I need to compare dates. The use case was to check if a persons membership had expired. I didn't think much of it till I started to develop it. The first trap I feel into was trying to create ranges and bucket sets. The other trap I fell into was not converting the date field to a complete date. This may seem obvious to most people but my Google searches came up with nothing so I thought I would create a quick post. I assume everyone knows how to create a decision table so I'm not going to go through those steps. The prerequisite for this post is to have a decision table with a payload that has a date field. This filed must have the date in the following format YYYY-MM-DDThh:mm:ss. Create a new condition in your decision table Right-click on the condition to edit it and select the expression builder In the expression builder, select the Functions tab. Expand the CurrentDate file and select date, and click Insert Into Expression button. In the Expression Builder you need to create an expression that will return true or false, add the operation <= after the CurrentDate.date In my scenario my date field is memberExpire, Navigate to your date field and expand, select toGregorianCalendar(). Your expression will look something like this, click OK to get back to the decision table Now its just a matter of checking if the value is true or false. Simple when you know how :-)

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  • Gracefully exiting from thread in Ruby

    - by jasonbogd
    Hi, I am trying out Mongrel and using the following code: require 'rubygems' require 'mongrel' class SimpleHandler < Mongrel::HttpHandler def process(request, response) response.start(200) do |head, out| head["Content-Type"] = "text/plain" out.write("Hello World!\n") end end end h = Mongrel::HttpServer.new("0.0.0.0", "3000") h.register("/test", SimpleHandler.new) puts "Press Control-C to exit" h.run.join trap("INT") do puts "Exiting..." end Basically, this just prints out "Hello World!" when I go to localhost:3000/test. It works fine, and I can close the program with Control-C. But when I press Control-C, this gets outputted: my_web_server.rb:17:in `join': Interrupt from my_web_server.rb:17 So I tried putting that trap("INT") statement at the end, but it isn't getting called. Solution? Thanks.

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  • Trapping errors in TClientDataSet.CommandText

    - by Rob McDonell
    I have a TClientDataSet connected to a TDataSetProvider, which in turn is connected to a TAdsTable. I set the SQL command and then open the ClientDataset something like this: try CDS.CommandText := 'SELECT * FROM tablename WHERE fieldname = 1'; CDS.Open except // trap exception here - this never gets executed! end; If the SQL statement in CommandText fails, however (syntax error or whatever) I get an exception within the Advantage code, but it never gets caught in my own exception handling code. Is there any way for me to trap this error and report it nicely to the user. Alternatively is there a way to verify the syntax of an SQL query before executing it? I'm using Delphi Pro 2009, and Advantage Local Server 9.

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  • CKeditor 3.0 - How to know which toolbar button is clicked

    - by understack
    Hi, I want to update few variables when any of the toolbar button (like bold, italic etc) is clicked. I'm unable to trap 'click' event on any of these buttons. Could somebody give me an example when clicking on 'bold' button would also pop up an alert box? How can I trap 'paste' event? I've googled a lot and searched ckeditor forum but couldn't find any solution. Any pointer would be really helpful. Thanks.

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  • Stopping httpd causes a process started from perl CGI script to receive SIGTERM

    - by Pranav Pal
    I am running a shell script from a perl CGI script: #!/usr/bin/perl my $command = "./script.sh &"; my $pid = fork(); if (defined($pid) && $pid==0) { # background process system( $command ); } The shell script looks like this: #!/bin/sh trap 'echo trapped' 15 tail -f test.log When I run the CGI script from browser, and then stop httpd using /etc/init.d/httpd stop, the script receives a SIGTERM signal. I was expecting the script to run as a separate process and not be tied in anyway to httpd. Though I can trap the SIGTERM, I would like to understand why the script is receiving SIGTERM at all. What wrong am I doing here? I am running RHEL 5.8 and Apache HTTP server 2.4. Thanks, Pranav

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  • Trappings MySQL Warnings on Calls Wrapped in Classes -- Python

    - by chernevik
    I can't get Python's try/else blocks to catch MySQL warnings when the execution statements are wrapped in classes. I have a class that has as a MySQL connection object as an attribute, a MySQL cursor object as another, and a method that run queries through that cursor object. The cursor is itself wrapped in a class. These seem to run queries properly, but the MySQL warnings they generate are not caught as exceptions in a try/else block. Why don't the try/else blocks catch the warnings? How would I revise the classes or method calls to catch the warnings? Also, I've looked through the prominent sources and can't find a discussion that helps me understand this. I'd appreciate any reference that explains this. Please see code below. Apologies for verbosity, I'm newbie. #!/usr/bin/python import MySQLdb import sys import copy sys.path.append('../../config') import credentials as c # local module with dbase connection credentials #============================================================================= # CLASSES #------------------------------------------------------------------------ class dbMySQL_Connection: def __init__(self, db_server, db_user, db_passwd): self.conn = MySQLdb.connect(db_server, db_user, db_passwd) def getCursor(self, dict_flag=True): self.dbMySQL_Cursor = dbMySQL_Cursor(self.conn, dict_flag) return self.dbMySQL_Cursor def runQuery(self, qryStr, dict_flag=True): qry_res = runQueryNoCursor(qryStr=qryStr, \ conn=self, \ dict_flag=dict_flag) return qry_res #------------------------------------------------------------------------ class dbMySQL_Cursor: def __init__(self, conn, dict_flag=True): if dict_flag: dbMySQL_Cursor = conn.cursor(MySQLdb.cursors.DictCursor) else: dbMySQL_Cursor = conn.cursor() self.dbMySQL_Cursor = dbMySQL_Cursor def closeCursor(self): self.dbMySQL_Cursor.close() #============================================================================= # QUERY FUNCTIONS #------------------------------------------------------------------------------ def runQueryNoCursor(qryStr, conn, dict_flag=True): dbMySQL_Cursor = conn.getCursor(dict_flag) qry_res =runQueryFnc(qryStr, dbMySQL_Cursor.dbMySQL_Cursor) dbMySQL_Cursor.closeCursor() return qry_res #------------------------------------------------------------------------------ def runQueryFnc(qryStr, dbMySQL_Cursor): qry_res = {} qry_res['rows'] = dbMySQL_Cursor.execute(qryStr) qry_res['result'] = copy.deepcopy(dbMySQL_Cursor.fetchall()) qry_res['messages'] = copy.deepcopy(dbMySQL_Cursor.messages) qry_res['query_str'] = qryStr return qry_res #============================================================================= # USAGES qry = 'DROP DATABASE IF EXISTS database_of_armaments' dbConn = dbMySQL_Connection(**c.creds) def dbConnRunQuery(): # Does not trap an exception; warning displayed to standard error. try: dbConn.runQuery(qry) except: print "dbConn.runQuery() caught an exception." def dbConnCursorExecute(): # Does not trap an exception; warning displayed to standard error. dbConn.getCursor() # try/except block does catches error without this try: dbConn.dbMySQL_Cursor.dbMySQL_Cursor.execute(qry) except Exception, e: print "dbConn.dbMySQL_Cursor.execute() caught an exception." print repr(e) def funcRunQueryNoCursor(): # Does not trap an exception; no warning displayed try: res = runQueryNoCursor(qry, dbConn) print 'Try worked. %s' % res except Exception, e: print "funcRunQueryNoCursor() caught an exception." print repr(e) #============================================================================= if __name__ == '__main__': print '\n' print 'EXAMPLE -- dbConnRunQuery()' dbConnRunQuery() print '\n' print 'EXAMPLE -- dbConnCursorExecute()' dbConnCursorExecute() print '\n' print 'EXAMPLE -- funcRunQueryNoCursor()' funcRunQueryNoCursor() print '\n'

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  • Oracle Solaris Cluster 4.2 Event and its SNMP Interface

    - by user12609115
    Background The cluster event SNMP interface was first introduced in Oracle Solaris Cluster 3.2 release. The details of the SNMP interface are described in the Oracle Solaris Cluster System Administration Guide and the Cluster 3.2 SNMP blog. Prior to the Oracle Solaris Cluster 4.2 release, when the event SNMP interface was enabled, it would take effect on WARNING or higher severity events. The events with WARNING or higher severity are usually for the status change of a cluster component from ONLINE to OFFLINE. The interface worked like an alert/alarm interface when some components in the cluster were out of service (changed to OFFLINE). The consumers of this interface could not get notification for all status changes and configuration changes in the cluster. Cluster Event and its SNMP Interface in Oracle Solaris Cluster 4.2 The user model of the cluster event SNMP interface is the same as what was provided in the previous releases. The cluster event SNMP interface is not enabled by default on a freshly installed cluster; you can enable it by using the cluster event SNMP administration commands on any cluster nodes. Usually, you only need to enable it on one of the cluster nodes or a subset of the cluster nodes because all cluster nodes get the same cluster events. When it is enabled, it is responsible for two basic tasks. • Logs up to 100 most recent NOTICE or higher severity events to the MIB. • Sends SNMP traps to the hosts that are configured to receive the above events. The changes in the Oracle Solaris Cluster 4.2 release are1) Introduction of the NOTICE severity for the cluster configuration and status change events.The NOTICE severity is introduced for the cluster event in the 4.2 release. It is the severity between the INFO and WARNING severity. Now all severities for the cluster events are (from low to high) • INFO (not exposed to the SNMP interface) • NOTICE (newly introduced in the 4.2 release) • WARNING • ERROR • CRITICAL • FATAL In the 4.2 release, the cluster event system is enhanced to make sure at least one event with the NOTICE or a higher severity will be generated when there is a configuration or status change from a cluster component instance. In other words, the cluster events from a cluster with the NOTICE or higher severities will cover all status and configuration changes in the cluster (include all component instances). The cluster component instance here refers to an instance of the following cluster componentsnode, quorum, resource group, resource, network interface, device group, disk, zone cluster and geo cluster heartbeat. For example, pnode1 is an instance of the cluster node component, and oracleRG is an instance of the cluster resource group. With the introduction of the NOTICE severity event, when the cluster event SNMP interface is enabled, the consumers of the SNMP interface will get notification for all status and configuration changes in the cluster. A thrid-party system management platform with the cluster SNMP interface integration can generate alarms and clear alarms programmatically, because it can get notifications for the status change from ONLINE to OFFLINE and also from OFFLINE to ONLINE. 2) Customization for the cluster event SNMP interface • The number of events logged to the MIB is 100. When the number of events stored in the MIB reaches 100 and a new qualified event arrives, the oldest event will be removed before storing the new event to the MIB (FIFO, first in, first out). The 100 is the default and minimum value for the number of events stored in the MIB. It can be changed by setting the log_number property value using the clsnmpmib command. The maximum number that can be set for the property is 500. • The cluster event SNMP interface takes effect on the NOTICE or high severity events. The NOTICE severity is also the default and lowest event severity for the SNMP interface. The SNMP interface can be configured to take effect on other higher severity events, such as WARNING or higher severity events by setting the min_severity property to the WARNING. When the min_severity property is set to the WARNING, the cluster event SNMP interface would behave the same as the previous releases (prior to the 4.2 release). Examples, • Set the number of events stored in the MIB to 200 # clsnmpmib set -p log_number=200 event • Set the interface to take effect on WARNING or higher severity events. # clsnmpmib set -p min_severity=WARNING event Administering the Cluster Event SNMP Interface Oracle Solaris Cluster provides the following three commands to administer the SNMP interface. • clsnmpmib: administer the SNMP interface, and the MIB configuration. • clsnmphost: administer hosts for the SNMP traps • clsnmpuser: administer SNMP users (specific for SNMP v3 protocol) Only clsnmpmib is changed in the 4.2 release to support the aforementioned customization of the SNMP interface. Here are some simple examples using the commands. Examples: 1. Enable the cluster event SNMP interface on the local node # clsnmpmib enable event 2. Display the status of the cluster event SNMP interface on the local node # clsnmpmib show -v 3. Configure my_host to receive the cluster event SNMP traps. # clsnmphost add my_host Cluster Event SNMP Interface uses the common agent container SNMP adaptor, which is based on the JDMK SNMP implementation as its SNMP agent infrastructure. By default, the port number for the SNMP MIB is 11161, and the port number for the SNMP traps is 11162. The port numbers can be changed by using the cacaoadm. For example, # cacaoadm list-params Print all changeable parameters. The output includes the snmp-adaptor-port and snmp-adaptor-trap-port properties. # cacaoadm set-param snmp-adaptor-port=1161 Set the SNMP MIB port number to 1161. # cacaoadm set-param snmp-adaptor-trap-port=1162 Set the SNMP trap port number to 1162. The cluster event SNMP MIB is defined in sun-cluster-event-mib.mib, which is located in the /usr/cluster/lib/mibdirectory. Its OID is 1.3.6.1.4.1.42.2.80, that can be used to walk through the MIB data. Again, for more detail information about the cluster event SNMP interface, please see the Oracle Solaris Cluster 4.2 System Administration Guide. - Leland Chen 

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  • Lessons from rewriting POP Forums for MVC, open source-like

    - by Jeff
    It has been a ton of work, interrupted over the last two years by unemployment, moving, a baby, failing to sell houses and other life events, but it's really exciting to see POP Forums v9 coming together. I'm not even sure when I decided to really commit to it as an open source project, but working on the same team as the CodePlex folks probably had something to do with it. Moving along the roadmap I set for myself, the app is now running on a quasi-production site... we launched MouseZoom last weekend. (That's a post-beta 1 build of the forum. There's also some nifty Silverlight DeepZoom goodness on that site.)I have to make a point to illustrate just how important starting over was for me. I started this forum thing for my sites in old ASP more than ten years ago. What a mess that stuff was, including SQL injection vulnerabilities and all kinds of crap. It went to ASP.NET in 2002, but even then, it felt a little too much like script. More than a year later, in 2003, I did an honest to goodness rewrite. If you've been in this business of writing code for any amount of time, you know how much you hate what you wrote a month ago, so just imagine that with seven years in between. The subsequent versions still carried a fair amount of crap, and that's why I had to start over, to make a clean break. Mind you, much of that crap is still running on some of my production sites in a stable manner, but it's a pain in the ass to maintain.So with that clean break, there is much that I have learned. These are a few of those lessons, in no particular order...Avoid shiny object syndromeOver the years, I've embraced new things without bothering to ask myself why. I remember spending the better part of a year trying to adapt this app to use the membership and profile API's in ASP.NET, just because they were there. They didn't solve any known problem. Early on in this version, I dabbled in exotic ORM's, even though I already had the fundamental SQL that I knew worked. I bloated up the client side code with all kinds of jQuery UI and plugins just because, and it got in the way. All the new shiny can be distracting, and I've come to realize that I've allowed it to be a distraction most of my professional life.Just query what you needI've spent a lot of time over-thinking how to query data. In the SQL world, this means exotic joins, special caches, the read-update-commit loop of ORM's, etc. There are times when you have to remind yourself that you aren't Facebook, you'll never be Facebook, and that databases are in fact intended to serve data. In a lot of projects, back in the day, I used to have these big, rich data objects and pass them all over the place, through various application tiers, when in reality, all I needed was some ID from the entity. I try to be mindful of how many queries hit the database on a given request, but I don't obsess over it. I just get what I need.Don't spend too much time worrying about your unit testsIf you've looked at any of the tests for POP Forums, you might offer an audible WTF. That's OK. There's a whole lot of mocking going on. In some cases, it points out where you're doing too much, and that's good for improving your design. In other cases it shows where your design sucks. But the biggest trap of unit testing is that you worry it should be prettier. That's a waste of time. When you write a test, in many cases before the production code, the important part is that you're testing the right thing. If you have to mock up a bunch of stuff to test the outcome, so be it, but it's not wasted time. You're still doing up the typical arrange-action-assert deal, and you'll be able to read that later if you need to.Get back to your HTTP rootsASP.NET Webforms did a reasonably decent job at abstracting us away from the stateless nature of the Web. A lot of people criticize it, but I think it all worked pretty well. These days, with MVC, jQuery, REST services, and what not, we've gone back to thinking about the wire. The nuts and bolts passing between our Web browser and server matters. This doesn't make things harder, in my opinion, it makes them easier. There is something incredibly freeing about how we approach development of Web apps now. HTTP is a really simple protocol, and the stuff we push through it, in particular HTML and JSON, are pretty simple too. The debugging points are really easy to trap and trace.Premature optimization is prematureI'll go back to the data thing for a moment. I've been known to look at a particular action or use case and stress about the number of calls that are made to the database. I'm not suggesting that it's a bad thing to keep these in mind, but if you worry about it outside of the context of the actual impact, you're wasting time. For example, I query the database for last read times in a forum separately of the user and the list of forums. The impact on performance barely exists. If I put it under load, exceeding the kind of load I expect, it still barely has an impact. Then consider it only counts for logged in users. The context of this "inefficient" action is that it doesn't matter. Did I mention I won't be Facebook?Solve your own problems firstThis is another trap I've fallen into. I've often thought about what other people might need for some feature or aspect of the app. In other words, I was willing to make design decisions based on non-existent data. How stupid is that? When I decided to truly open source this thing, building for myself first was a stated design goal. This app has to server the audiences of CoasterBuzz, MouseZoom and other sites first. In this development scenario, you don't have access to mountains of usability studies or user focus groups. You have to start with what you know.I'm sure there are other points I could make too. It has been a lot of fun to work on, and I look forward to evolving the UI as time goes on. That's where I hope to see more magic in the future.

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  • The Complexities to Creating Real Electronic Health Records

    <b>Linux Journal:</b> "But with all of this focus on streamlining and digitally electrifying health records, I began to wonder where did the Open Source community stand and where is its input? There is certainly a lot of money sitting out there for someone who wants to try to build the better mouse trap."

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