python datetime - Page 474

How to index pdf, ppt, xl files in lucene (java based or python or php any of these is fine)?

- by harsha

Also I want to know how to add meta data while indexing so that i can boost some parameters

Interpreted vs. Compiled Languages for Web Sites (PHP, ASP, Perl, Python, etc.)

I build database-driven web sites. Previously I have used Perl or PHP with MySQL. Now I am starting a big new project, and I want to do it in the way that will result in the most responsive possible site. I have seen several pages here where questions about how to optimize PHP are criticized with various versions of "it's not worth going to great lengths to optimize PHP since it's an interpreted language and it won't make that much difference". I have also heard various discussions (especiallon on the SO podcast) about the benefits of compiled vs. interpreted languages, and it seems as though it would be in my interests to use a compiled language to serve up the site instead of an interpreted language. Is this even possible in a web context? If so, what would be a reasonable language choice? In addition to speed one benefit I forsee is the possiblity of finding bugs at compile time instead of having to debug the web site. Is this reasonable to expect?

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Why should main() be short?

- by Stargazer712

I've been programming for over 9 years, and according to the advice of my first programming teacher, I always keep my main() function extremely short. At first I had no idea why. I just obeyed without understanding, much to the delight of my professors. After gaining experience, I realized that if I designed my code correctly, having a short main() function just sortof happened. Writing modularized code and following the single responsibility principle allowed my code to be designed in "bunches", and main() served as nothing more than a catalyst to get the program running. Fast forward to a few weeks ago, I was looking at Python's souce code, and I found the main() function: /* Minimal main program -- everything is loaded from the library */ ... int main(int argc, char **argv) { ... return Py_Main(argc, argv); } Yay Python. Short main() function == Good code. Programming teachers were right. Wanting to look deeper, I took a look at Py_Main. In its entirety, it is defined as follows: /* Main program */ int Py_Main(int argc, char **argv) { int c; int sts; char *command = NULL; char *filename = NULL; char *module = NULL; FILE *fp = stdin; char *p; int unbuffered = 0; int skipfirstline = 0; int stdin_is_interactive = 0; int help = 0; int version = 0; int saw_unbuffered_flag = 0; PyCompilerFlags cf; cf.cf_flags = 0; orig_argc = argc; /* For Py_GetArgcArgv() */ orig_argv = argv; #ifdef RISCOS Py_RISCOSWimpFlag = 0; #endif PySys_ResetWarnOptions(); while ((c = _PyOS_GetOpt(argc, argv, PROGRAM_OPTS)) != EOF) { if (c == 'c') { /* -c is the last option; following arguments that look like options are left for the command to interpret. */ command = (char *)malloc(strlen(_PyOS_optarg) + 2); if (command == NULL) Py_FatalError( "not enough memory to copy -c argument"); strcpy(command, _PyOS_optarg); strcat(command, "\n"); break; } if (c == 'm') { /* -m is the last option; following arguments that look like options are left for the module to interpret. */ module = (char *)malloc(strlen(_PyOS_optarg) + 2); if (module == NULL) Py_FatalError( "not enough memory to copy -m argument"); strcpy(module, _PyOS_optarg); break; } switch (c) { case 'b': Py_BytesWarningFlag++; break; case 'd': Py_DebugFlag++; break; case '3': Py_Py3kWarningFlag++; if (!Py_DivisionWarningFlag) Py_DivisionWarningFlag = 1; break; case 'Q': if (strcmp(_PyOS_optarg, "old") == 0) { Py_DivisionWarningFlag = 0; break; } if (strcmp(_PyOS_optarg, "warn") == 0) { Py_DivisionWarningFlag = 1; break; } if (strcmp(_PyOS_optarg, "warnall") == 0) { Py_DivisionWarningFlag = 2; break; } if (strcmp(_PyOS_optarg, "new") == 0) { /* This only affects __main__ */ cf.cf_flags |= CO_FUTURE_DIVISION; /* And this tells the eval loop to treat BINARY_DIVIDE as BINARY_TRUE_DIVIDE */ _Py_QnewFlag = 1; break; } fprintf(stderr, "-Q option should be `-Qold', " "`-Qwarn', `-Qwarnall', or `-Qnew' only\n"); return usage(2, argv[0]); /* NOTREACHED */ case 'i': Py_InspectFlag++; Py_InteractiveFlag++; break; /* case 'J': reserved for Jython */ case 'O': Py_OptimizeFlag++; break; case 'B': Py_DontWriteBytecodeFlag++; break; case 's': Py_NoUserSiteDirectory++; break; case 'S': Py_NoSiteFlag++; break; case 'E': Py_IgnoreEnvironmentFlag++; break; case 't': Py_TabcheckFlag++; break; case 'u': unbuffered++; saw_unbuffered_flag = 1; break; case 'v': Py_VerboseFlag++; break; #ifdef RISCOS case 'w': Py_RISCOSWimpFlag = 1; break; #endif case 'x': skipfirstline = 1; break; /* case 'X': reserved for implementation-specific arguments */ case 'U': Py_UnicodeFlag++; break; case 'h': case '?': help++; break; case 'V': version++; break; case 'W': PySys_AddWarnOption(_PyOS_optarg); break; /* This space reserved for other options */ default: return usage(2, argv[0]); /*NOTREACHED*/ } } if (help) return usage(0, argv[0]); if (version) { fprintf(stderr, "Python %s\n", PY_VERSION); return 0; } if (Py_Py3kWarningFlag && !Py_TabcheckFlag) /* -3 implies -t (but not -tt) */ Py_TabcheckFlag = 1; if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') Py_InspectFlag = 1; if (!saw_unbuffered_flag && (p = Py_GETENV("PYTHONUNBUFFERED")) && *p != '\0') unbuffered = 1; if (!Py_NoUserSiteDirectory && (p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0') Py_NoUserSiteDirectory = 1; if ((p = Py_GETENV("PYTHONWARNINGS")) && *p != '\0') { char *buf, *warning; buf = (char *)malloc(strlen(p) + 1); if (buf == NULL) Py_FatalError( "not enough memory to copy PYTHONWARNINGS"); strcpy(buf, p); for (warning = strtok(buf, ","); warning != NULL; warning = strtok(NULL, ",")) PySys_AddWarnOption(warning); free(buf); } if (command == NULL && module == NULL && _PyOS_optind < argc && strcmp(argv[_PyOS_optind], "-") != 0) { #ifdef __VMS filename = decc$translate_vms(argv[_PyOS_optind]); if (filename == (char *)0 || filename == (char *)-1) filename = argv[_PyOS_optind]; #else filename = argv[_PyOS_optind]; #endif } stdin_is_interactive = Py_FdIsInteractive(stdin, (char *)0); if (unbuffered) { #if defined(MS_WINDOWS) || defined(__CYGWIN__) _setmode(fileno(stdin), O_BINARY); _setmode(fileno(stdout), O_BINARY); #endif #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stderr, (char *)NULL, _IONBF, BUFSIZ); #else /* !HAVE_SETVBUF */ setbuf(stdin, (char *)NULL); setbuf(stdout, (char *)NULL); setbuf(stderr, (char *)NULL); #endif /* !HAVE_SETVBUF */ } else if (Py_InteractiveFlag) { #ifdef MS_WINDOWS /* Doesn't have to have line-buffered -- use unbuffered */ /* Any set[v]buf(stdin, ...) screws up Tkinter :-( */ setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); #else /* !MS_WINDOWS */ #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IOLBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IOLBF, BUFSIZ); #endif /* HAVE_SETVBUF */ #endif /* !MS_WINDOWS */ /* Leave stderr alone - it should be unbuffered anyway. */ } #ifdef __VMS else { setvbuf (stdout, (char *)NULL, _IOLBF, BUFSIZ); } #endif /* __VMS */ #ifdef __APPLE__ /* On MacOS X, when the Python interpreter is embedded in an application bundle, it gets executed by a bootstrapping script that does os.execve() with an argv[0] that's different from the actual Python executable. This is needed to keep the Finder happy, or rather, to work around Apple's overly strict requirements of the process name. However, we still need a usable sys.executable, so the actual executable path is passed in an environment variable. See Lib/plat-mac/bundlebuiler.py for details about the bootstrap script. */ if ((p = Py_GETENV("PYTHONEXECUTABLE")) && *p != '\0') Py_SetProgramName(p); else Py_SetProgramName(argv[0]); #else Py_SetProgramName(argv[0]); #endif Py_Initialize(); if (Py_VerboseFlag || (command == NULL && filename == NULL && module == NULL && stdin_is_interactive)) { fprintf(stderr, "Python %s on %s\n", Py_GetVersion(), Py_GetPlatform()); if (!Py_NoSiteFlag) fprintf(stderr, "%s\n", COPYRIGHT); } if (command != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } if (module != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' so that PySys_SetArgv correctly sets sys.path[0] to '' rather than looking for a file called "-m". See tracker issue #8202 for details. */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } PySys_SetArgv(argc-_PyOS_optind, argv+_PyOS_optind); if ((Py_InspectFlag || (command == NULL && filename == NULL && module == NULL)) && isatty(fileno(stdin))) { PyObject *v; v = PyImport_ImportModule("readline"); if (v == NULL) PyErr_Clear(); else Py_DECREF(v); } if (command) { sts = PyRun_SimpleStringFlags(command, &cf) != 0; free(command); } else if (module) { sts = RunModule(module, 1); free(module); } else { if (filename == NULL && stdin_is_interactive) { Py_InspectFlag = 0; /* do exit on SystemExit */ RunStartupFile(&cf); } /* XXX */ sts = -1; /* keep track of whether we've already run __main__ */ if (filename != NULL) { sts = RunMainFromImporter(filename); } if (sts==-1 && filename!=NULL) { if ((fp = fopen(filename, "r")) == NULL) { fprintf(stderr, "%s: can't open file '%s': [Errno %d] %s\n", argv[0], filename, errno, strerror(errno)); return 2; } else if (skipfirstline) { int ch; /* Push back first newline so line numbers remain the same */ while ((ch = getc(fp)) != EOF) { if (ch == '\n') { (void)ungetc(ch, fp); break; } } } { /* XXX: does this work on Win/Win64? (see posix_fstat) */ struct stat sb; if (fstat(fileno(fp), &sb) == 0 && S_ISDIR(sb.st_mode)) { fprintf(stderr, "%s: '%s' is a directory, cannot continue\n", argv[0], filename); fclose(fp); return 1; } } } if (sts==-1) { /* call pending calls like signal handlers (SIGINT) */ if (Py_MakePendingCalls() == -1) { PyErr_Print(); sts = 1; } else { sts = PyRun_AnyFileExFlags( fp, filename == NULL ? "<stdin>" : filename, filename != NULL, &cf) != 0; } } } /* Check this environment variable at the end, to give programs the * opportunity to set it from Python. */ if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') { Py_InspectFlag = 1; } if (Py_InspectFlag && stdin_is_interactive && (filename != NULL || command != NULL || module != NULL)) { Py_InspectFlag = 0; /* XXX */ sts = PyRun_AnyFileFlags(stdin, "<stdin>", &cf) != 0; } Py_Finalize(); #ifdef RISCOS if (Py_RISCOSWimpFlag) fprintf(stderr, "\x0cq\x0c"); /* make frontend quit */ #endif #ifdef __INSURE__ /* Insure++ is a memory analysis tool that aids in discovering * memory leaks and other memory problems. On Python exit, the * interned string dictionary is flagged as being in use at exit * (which it is). Under normal circumstances, this is fine because * the memory will be automatically reclaimed by the system. Under * memory debugging, it's a huge source of useless noise, so we * trade off slower shutdown for less distraction in the memory * reports. -baw */ _Py_ReleaseInternedStrings(); #endif /* __INSURE__ */ return sts; } Good God Almighty...it is big enough to sink the Titanic. It seems as though Python did the "Intro to Programming 101" trick and just moved all of main()'s code to a different function called it something very similar to "main". Here's my question: Is this code terribly written, or are there other reasons reasons to have a short main function? As it stands right now, I see absolutely no difference between doing this and just moving the code in Py_Main() back into main(). Am I wrong in thinking this?

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Why should main() be short?

- by Stargazer712

I've been programming for over 9 years, and according to the advice of my first programming teacher, I always keep my main() function extremely short. At first I had no idea why. I just obeyed without understanding, much to the delight of my professors. After gaining experience, I realized that if I designed my code correctly, having a short main() function just sortof happened. Writing modularized code and following the single responsibility principle allowed my code to be designed in "bunches", and main() served as nothing more than a catalyst to get the program running. Fast forward to a few weeks ago, I was looking at Python's souce code, and I found the main() function: /* Minimal main program -- everything is loaded from the library */ ... int main(int argc, char **argv) { ... return Py_Main(argc, argv); } Yay python. Short main() function == Good code. Programming teachers were right. Wanting to look deeper, I took a look at Py_Main. In its entirety, it is defined as follows: /* Main program */ int Py_Main(int argc, char **argv) { int c; int sts; char *command = NULL; char *filename = NULL; char *module = NULL; FILE *fp = stdin; char *p; int unbuffered = 0; int skipfirstline = 0; int stdin_is_interactive = 0; int help = 0; int version = 0; int saw_unbuffered_flag = 0; PyCompilerFlags cf; cf.cf_flags = 0; orig_argc = argc; /* For Py_GetArgcArgv() */ orig_argv = argv; #ifdef RISCOS Py_RISCOSWimpFlag = 0; #endif PySys_ResetWarnOptions(); while ((c = _PyOS_GetOpt(argc, argv, PROGRAM_OPTS)) != EOF) { if (c == 'c') { /* -c is the last option; following arguments that look like options are left for the command to interpret. */ command = (char *)malloc(strlen(_PyOS_optarg) + 2); if (command == NULL) Py_FatalError( "not enough memory to copy -c argument"); strcpy(command, _PyOS_optarg); strcat(command, "\n"); break; } if (c == 'm') { /* -m is the last option; following arguments that look like options are left for the module to interpret. */ module = (char *)malloc(strlen(_PyOS_optarg) + 2); if (module == NULL) Py_FatalError( "not enough memory to copy -m argument"); strcpy(module, _PyOS_optarg); break; } switch (c) { case 'b': Py_BytesWarningFlag++; break; case 'd': Py_DebugFlag++; break; case '3': Py_Py3kWarningFlag++; if (!Py_DivisionWarningFlag) Py_DivisionWarningFlag = 1; break; case 'Q': if (strcmp(_PyOS_optarg, "old") == 0) { Py_DivisionWarningFlag = 0; break; } if (strcmp(_PyOS_optarg, "warn") == 0) { Py_DivisionWarningFlag = 1; break; } if (strcmp(_PyOS_optarg, "warnall") == 0) { Py_DivisionWarningFlag = 2; break; } if (strcmp(_PyOS_optarg, "new") == 0) { /* This only affects __main__ */ cf.cf_flags |= CO_FUTURE_DIVISION; /* And this tells the eval loop to treat BINARY_DIVIDE as BINARY_TRUE_DIVIDE */ _Py_QnewFlag = 1; break; } fprintf(stderr, "-Q option should be `-Qold', " "`-Qwarn', `-Qwarnall', or `-Qnew' only\n"); return usage(2, argv[0]); /* NOTREACHED */ case 'i': Py_InspectFlag++; Py_InteractiveFlag++; break; /* case 'J': reserved for Jython */ case 'O': Py_OptimizeFlag++; break; case 'B': Py_DontWriteBytecodeFlag++; break; case 's': Py_NoUserSiteDirectory++; break; case 'S': Py_NoSiteFlag++; break; case 'E': Py_IgnoreEnvironmentFlag++; break; case 't': Py_TabcheckFlag++; break; case 'u': unbuffered++; saw_unbuffered_flag = 1; break; case 'v': Py_VerboseFlag++; break; #ifdef RISCOS case 'w': Py_RISCOSWimpFlag = 1; break; #endif case 'x': skipfirstline = 1; break; /* case 'X': reserved for implementation-specific arguments */ case 'U': Py_UnicodeFlag++; break; case 'h': case '?': help++; break; case 'V': version++; break; case 'W': PySys_AddWarnOption(_PyOS_optarg); break; /* This space reserved for other options */ default: return usage(2, argv[0]); /*NOTREACHED*/ } } if (help) return usage(0, argv[0]); if (version) { fprintf(stderr, "Python %s\n", PY_VERSION); return 0; } if (Py_Py3kWarningFlag && !Py_TabcheckFlag) /* -3 implies -t (but not -tt) */ Py_TabcheckFlag = 1; if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') Py_InspectFlag = 1; if (!saw_unbuffered_flag && (p = Py_GETENV("PYTHONUNBUFFERED")) && *p != '\0') unbuffered = 1; if (!Py_NoUserSiteDirectory && (p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0') Py_NoUserSiteDirectory = 1; if ((p = Py_GETENV("PYTHONWARNINGS")) && *p != '\0') { char *buf, *warning; buf = (char *)malloc(strlen(p) + 1); if (buf == NULL) Py_FatalError( "not enough memory to copy PYTHONWARNINGS"); strcpy(buf, p); for (warning = strtok(buf, ","); warning != NULL; warning = strtok(NULL, ",")) PySys_AddWarnOption(warning); free(buf); } if (command == NULL && module == NULL && _PyOS_optind < argc && strcmp(argv[_PyOS_optind], "-") != 0) { #ifdef __VMS filename = decc$translate_vms(argv[_PyOS_optind]); if (filename == (char *)0 || filename == (char *)-1) filename = argv[_PyOS_optind]; #else filename = argv[_PyOS_optind]; #endif } stdin_is_interactive = Py_FdIsInteractive(stdin, (char *)0); if (unbuffered) { #if defined(MS_WINDOWS) || defined(__CYGWIN__) _setmode(fileno(stdin), O_BINARY); _setmode(fileno(stdout), O_BINARY); #endif #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stderr, (char *)NULL, _IONBF, BUFSIZ); #else /* !HAVE_SETVBUF */ setbuf(stdin, (char *)NULL); setbuf(stdout, (char *)NULL); setbuf(stderr, (char *)NULL); #endif /* !HAVE_SETVBUF */ } else if (Py_InteractiveFlag) { #ifdef MS_WINDOWS /* Doesn't have to have line-buffered -- use unbuffered */ /* Any set[v]buf(stdin, ...) screws up Tkinter :-( */ setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); #else /* !MS_WINDOWS */ #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IOLBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IOLBF, BUFSIZ); #endif /* HAVE_SETVBUF */ #endif /* !MS_WINDOWS */ /* Leave stderr alone - it should be unbuffered anyway. */ } #ifdef __VMS else { setvbuf (stdout, (char *)NULL, _IOLBF, BUFSIZ); } #endif /* __VMS */ #ifdef __APPLE__ /* On MacOS X, when the Python interpreter is embedded in an application bundle, it gets executed by a bootstrapping script that does os.execve() with an argv[0] that's different from the actual Python executable. This is needed to keep the Finder happy, or rather, to work around Apple's overly strict requirements of the process name. However, we still need a usable sys.executable, so the actual executable path is passed in an environment variable. See Lib/plat-mac/bundlebuiler.py for details about the bootstrap script. */ if ((p = Py_GETENV("PYTHONEXECUTABLE")) && *p != '\0') Py_SetProgramName(p); else Py_SetProgramName(argv[0]); #else Py_SetProgramName(argv[0]); #endif Py_Initialize(); if (Py_VerboseFlag || (command == NULL && filename == NULL && module == NULL && stdin_is_interactive)) { fprintf(stderr, "Python %s on %s\n", Py_GetVersion(), Py_GetPlatform()); if (!Py_NoSiteFlag) fprintf(stderr, "%s\n", COPYRIGHT); } if (command != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } if (module != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' so that PySys_SetArgv correctly sets sys.path[0] to '' rather than looking for a file called "-m". See tracker issue #8202 for details. */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } PySys_SetArgv(argc-_PyOS_optind, argv+_PyOS_optind); if ((Py_InspectFlag || (command == NULL && filename == NULL && module == NULL)) && isatty(fileno(stdin))) { PyObject *v; v = PyImport_ImportModule("readline"); if (v == NULL) PyErr_Clear(); else Py_DECREF(v); } if (command) { sts = PyRun_SimpleStringFlags(command, &cf) != 0; free(command); } else if (module) { sts = RunModule(module, 1); free(module); } else { if (filename == NULL && stdin_is_interactive) { Py_InspectFlag = 0; /* do exit on SystemExit */ RunStartupFile(&cf); } /* XXX */ sts = -1; /* keep track of whether we've already run __main__ */ if (filename != NULL) { sts = RunMainFromImporter(filename); } if (sts==-1 && filename!=NULL) { if ((fp = fopen(filename, "r")) == NULL) { fprintf(stderr, "%s: can't open file '%s': [Errno %d] %s\n", argv[0], filename, errno, strerror(errno)); return 2; } else if (skipfirstline) { int ch; /* Push back first newline so line numbers remain the same */ while ((ch = getc(fp)) != EOF) { if (ch == '\n') { (void)ungetc(ch, fp); break; } } } { /* XXX: does this work on Win/Win64? (see posix_fstat) */ struct stat sb; if (fstat(fileno(fp), &sb) == 0 && S_ISDIR(sb.st_mode)) { fprintf(stderr, "%s: '%s' is a directory, cannot continue\n", argv[0], filename); fclose(fp); return 1; } } } if (sts==-1) { /* call pending calls like signal handlers (SIGINT) */ if (Py_MakePendingCalls() == -1) { PyErr_Print(); sts = 1; } else { sts = PyRun_AnyFileExFlags( fp, filename == NULL ? "<stdin>" : filename, filename != NULL, &cf) != 0; } } } /* Check this environment variable at the end, to give programs the * opportunity to set it from Python. */ if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') { Py_InspectFlag = 1; } if (Py_InspectFlag && stdin_is_interactive && (filename != NULL || command != NULL || module != NULL)) { Py_InspectFlag = 0; /* XXX */ sts = PyRun_AnyFileFlags(stdin, "<stdin>", &cf) != 0; } Py_Finalize(); #ifdef RISCOS if (Py_RISCOSWimpFlag) fprintf(stderr, "\x0cq\x0c"); /* make frontend quit */ #endif #ifdef __INSURE__ /* Insure++ is a memory analysis tool that aids in discovering * memory leaks and other memory problems. On Python exit, the * interned string dictionary is flagged as being in use at exit * (which it is). Under normal circumstances, this is fine because * the memory will be automatically reclaimed by the system. Under * memory debugging, it's a huge source of useless noise, so we * trade off slower shutdown for less distraction in the memory * reports. -baw */ _Py_ReleaseInternedStrings(); #endif /* __INSURE__ */ return sts; } Good God Almighty...it is big enough to sink the Titanic. It seems as though Python did the "Intro to Programming 101" trick and just moved all of main()'s code to a different function called it something very similar to "main". Here's my question: Is this code terribly written, or are there other reasons to have a short main function? As it stands right now, I see absolutely no difference between doing this and just moving the code in Py_Main() back into main(). Am I wrong in thinking this?

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Unable to install mod_wsgi on CentOS 5.5 VPS...

- by jasonaburton

I am trying to install mod_wsgi on my VPS, but it won't work. This is what I am doing: wget http://modwsgi.googlecode.com/files/mod_wsgi-2.5.tar.gz tar xzvf mod_wsgi-2.5.tar.gz cd mod_wsgi-2.5 ./configure --with-python=/opt/python2.5/bin/python After I run the above command, I get this error: checking for apxs2... no checking for apxs... no checking Apache version... ./configure: line 1298: apxs: command not found ./configure: line 1298: apxs: command not found ./configure: line 1299: /: is a directory ./configure: line 1461: apxs: command not found configure: creating ./config.status config.status: creating Makefile config.status: error: cannot find input file: Makefile.in Through some research I've discovered that I need to modify my command: ./configure --with-apxs=/usr/local/apache/bin/apxs \ --with-python=/usr/local/bin/python But, /usr/local/apache/ doesn't exist, or so that's what it is telling me. If it doesn't exist, how do I create it with all the files needed, or if apache is located elsewhere on my VPS where would it be located? I'd also like to mention that I ran a command to install apache before this entire deal: yum install httpd so I assumed that was all I needed but apparently not (I am very new at all this server administration stuff so please be gentle) EDIT: This is the tutorial that I have been using to get this all set up: http://binarysushi.com/blog/2009/aug/19/CentOS-5-3-python-2-5-virtualevn-mod-wsgi-and-mod-rpaf/ I got stuck at the heading "Installing mod_wsgi" Thanks for any help!

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django fcgi - call a management command with subprocess.Popen

- by user41855

Hi, I'm using an app called django-chronograph. It has a code of line which works in my dev environment and does not work in production: p = subprocess.Popen(['python', get_manage_py(), 'run_job', str(self.pk)]) This line crashes in production with: unknown command run_job Whereas when I run directly from command line: manage.py run_job It works fine. Interestingly it worked once when we exchanged 'python' with 'usr/bin/python'. then we restarted the server once more and it was back to old behaviour. Thus it seems as we have a python path issue. I'm not the guy who is running the server, its my app that should run and it would be great to get some help here. Attention: I'm a total noob regarding server-administration.. server environment: NGINX with FCGI-Daemon FCGI in prefork-mode

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Whats the best way to update Ubuntu 9.04?

- by Fu86

I have a Ubuntu 9.04 server which has no packase support anymore. If I want to update my package lists, I get th following errors: Err http://de.archive.ubuntu.com jaunty-security/multiverse Packages 404 Not Found [IP: 141.30.13.10 80] W: Failed to fetch http://de.archive.ubuntu.com/ubuntu/dists/jaunty/main/binary-amd64/Packages 404 Not Found [IP: 141.30.13.10 80] .... I read at the official Ubuntu-Support-Page, that there is a update-manager-core-Package to upgrade to a new release. Unfortunately I dont have this package installed and I am unable to install it because of the lack of package sources. EDIT: Installing the package update-manager-core from another release doesn't work because it depends on a higher version of python-apt. (Tried with 10.04) $ dpkg -i update-manager-core_0.134.7_amd64.deb Selecting previously deselected package update-manager-core. (Reading database ... 28743 files and directories currently installed.) Unpacking update-manager-core (from update-manager-core_0.134.7_amd64.deb) ... dpkg: dependency problems prevent configuration of update-manager-core: update-manager-core depends on python-apt (>= 0.7.13.4ubuntu3); however: Version of python-apt on system is 0.7.9~exp2ubuntu10. update-manager-core depends on python-gnupginterface; however: Package python-gnupginterface is not installed. dpkg: error processing update-manager-core (--install): dependency problems - leaving unconfigured Errors were encountered while processing: update-manager-core So, whats the best way to upgrade to to current Release without reinstalling the complete (virtual) server?

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Host wildcard subdomains using postfix.

- by Jack M.

I'm trying to work out how I can get postfix to accept email for any sub-domain of my main site. I don't have virtual domains, just a long list of sub-domains for local delivery. In specific, I'm feeding python@*.mydomain.com into a Python using the alias file: python: |/www/proc_email.py The Python can handle delivery from there. I envision this looking something along the lines of: mydestination = encendio, localhost.localdomain, localhost, *.mydomain.com I'm running the latest version of postfix on Ubuntu (not rightly sure how to check the version). Thanks in advance.

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yum list installed including version of all installed packages CentOS 5.4

- by Andy

I have a list of packages installed with yum on CentOS 5.4 [root@server ~]# yum list installed ... Installed Packages GConf2.x86_64 2.14.0-9.el5 installed ImageMagick.x86_64 6.2.8.0-4.el5_1.1 installed MAKEDEV.x86_64 3.23-1.2 installed MySQL-python.x86_64 1.2.1-1 installed I would like to download these rpms locally using yumdownloader --resolve MySQL-python-1.2.1-1.x86_64 etc. However the package formatting is different (MySQL-python.x86_64 1.2.1-1 vs MySQL-python-1.2.1-1.x86_64) so I am unable to download them using the above command. I don't want to have to parse the output of yum list installed, and I also don't want to use the contents of /var/log/yum.log* as I'll have to account for erased packages and version discrepancies. However /var/log/yum.log* does have the formatting I require... May 25 14:58:15 Installed: groff-1.18.1.1-11.1.x86_64 May 25 14:58:15 Installed: bzip2-1.0.3-4.el5_2.x86_64 Any suggestions?

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Change date in a SQL query to reference a cell in Excel

- by Adil

I have the following code that returns the needed data into excel and manually changing the date will change the returned data; however, I'd like to reference a cell with a formula that will make the query a bit more user friendly. I've tried using my limited knowledge of referencing a cell but none have worked. This information is in cell A1 and the query is placed in cell A2 with the following equation: =wwQuery("STKAP03", $A$1) SET QUOTED_IDENTIFIER OFF SELECT * FROM OPENQUERY(INSQL, "SELECT DateTime, [40_MOTORS.MI436423.CIN], [40_MOTORS.MI436425.CIN] FROM WideHistory WHERE [40_MOTORS.MI436423.CIN] IS NOT NULL AND wwRetrievalMode = 'Delta' AND wwVersion = 'Latest' AND DateTime >='20120409 07:00:00' These two dates/times I'd like to reference cells on a different sheet AND DateTime <= '20120416 07:00:00'")

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Download file from vbscript?

- by Eye of Hell

I need a script that can be run on freshly installed windows xp+ and download specified files from internet, like http://www.python.org/ftp/python/2.6.2/python-2.6.2.msi Is it any easy way to do it without hand-crafting HTTP/FTP requests or using third-party programs like wget? I can suggest that WScript.CreateObject("internetexplorer.application") will do the magic, but documentation on it is extremely huge and Google is silent, as always :).

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How to make Windows command prompt treat single quote as though it is a double quote?

- by mark

My scenario is simple - I am copying script samples from the Mercurial online book (at http://hGBook.red-bean.com) and pasting them in a Windows command prompt. The problem is that the samples in the book use single quoted strings. When a single quoted string is passed on the Windows command prompt, the latter does not recognize that everything between the single quotes belongs to one string. For example, the following command: hg commit -m 'Initial commit' cannot be pasted as is in a command prompt, because the latter treats 'Initial commit' as two strings - 'Initial and commit'. I have to edit the command after paste and it is annoying. Is it possible to instruct the Windows command prompt to treat single quotes similarly to the double one? EDIT Following the reply by JdeBP I have done a little research. Here is the summary: Mercurial entry point looks like so (it is a python program): def run(): "run the command in sys.argv" sys.exit(dispatch(request(sys.argv[1:]))) So, I have created a tiny python program to mimic the command line processing used by mercurial: import sys print sys.argv[1:] Here is the Unix console log: [hg@Quake ~]$ python 1.py "1 2 3" ['1 2 3'] [hg@Quake ~]$ python 1.py '1 2 3' ['1 2 3'] [hg@Quake ~]$ python 1.py 1 2 3 ['1', '2', '3'] [hg@Quake ~]$ And here is the respective Windows console log: C:\Workpython 1.py "1 2 3" ['1 2 3'] C:\Workpython 1.py '1 2 3' ["'1", '2', "3'"] C:\Workpython 1.py 1 2 3 ['1', '2', '3'] C:\Work One can clearly see that Windows does not treat single quotes as double quotes. And this is the essence of my question.

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No Commands are Working on Mac OS X Terminal?

- by Raiders

When I run terminal using the icon on my desktop, I get this error: -bash: export: `:/System/Library/Frameworks/Python.framework/Versions/2.6/bin:/Library/Frameworks/Python.framework/Versions/2.6/bin:/Library/Frameworks/Python.framework/Versions/2.6/bin:/usr/local/mysql/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin': not a valid identifier And subsequently, no commands are working (ls, ssh, sudo, rm, cp and so forth). What is happening???

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How to copy the value from a cell to another (using a formula), but not formula from the source cell

- by RODY ROY

I'm making use of NOW() function at many places in my spreadsheet, which is basically a checklist document. So my requirement is that for each step, it should record the datetime at which that step was completed. But whenever the Now() is being used... all the previously updated cells withe datetime are also getting updated again. Hence at the end of the day, am not able to get the detailed time at which each of those steps are completed. This is how I've created as of now: Used a Checkbox for each step. Once the step is complete, on clicking the Checkbox, it will update the cell A1 as "Completed". In the cell B1, I've put the following function which will check for the value in A1. If it is "Completed", then it will update the value of B1 with the current datetime using Now() =IF(A1="Completed";NOW();"") Please let me know a solution for this. Also if there any other alternative.

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unittest import error with virtualenv + google-app-engine-django

- by Ray Yun

I'm working with google-app-engine-django + zipped django. Just running "python manage.py test" succeeded without error. But with virtualenv, test was failed with "import unittest error". same error with Django 1.1. - OSX 10.5.6 - google-app-engine-django (r101 via svn) : r100 was failed with launcher 1.3.0 - GoogleAppLauncher 1.3.0 - Django 1.1 & 1.1.1 (zipped) : both failed - virtualenv 1.4.5 - virtualenvwrapper 1.24 Error Message: (django_appengine)Reiot:warclouds Reiot$ python manage.py test WARNING:root:Could not read datastore data from /var/folders/UZ/UZ1vQeLFH2ShHk4kIiLcFk+++TI/-Tmp-/django_google-app-engine-django.datastore INFO:root:zipimporter('/Volumes/data/Documents/warclouds/django.zip', 'django/core/serializers/') .WARNING:root:Can't open zipfile /Users/Reiot/.virtualenvs/django_appengine/lib/python2.5/site-packages/setuptools-0.6c11-py2.5.egg: IOError: [Errno 13] file not accessible: '/Users/Reiot/.virtualenvs/django_appengine/lib/python2.5/site-packages/setuptools-0.6c11-py2.5.egg' WARNING:root:Can't open zipfile /Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/setuptools-0.6c9-py2.5.egg: IOError: [Errno 13] file not accessible: '/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/setuptools-0.6c9-py2.5.egg' ERROR:root:Exception encountered handling request Traceback (most recent call last): File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 3177, in _HandleRequest self._Dispatch(dispatcher, self.rfile, outfile, env_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 3120, in _Dispatch base_env_dict=env_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 515, in Dispatch base_env_dict=base_env_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 2379, in Dispatch self._module_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 2289, in ExecuteCGI reset_modules = exec_script(handler_path, cgi_path, hook) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 2185, in ExecuteOrImportScript exec module_code in script_module.__dict__ File "/Volumes/data/Documents/warclouds/main.py", line 28, in <module> from appengine_django import InstallAppengineHelperForDjango File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1264, in Decorate return func(self, *args, **kwargs) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1914, in load_module return self.FindAndLoadModule(submodule, fullname, search_path) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1264, in Decorate return func(self, *args, **kwargs) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1816, in FindAndLoadModule description) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1264, in Decorate return func(self, *args, **kwargs) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1767, in LoadModuleRestricted description) File "/Volumes/data/Documents/warclouds/appengine_django/__init__.py", line 44, in <module> import unittest ImportError: No module named unittest INFO:root:"GET / HTTP/1.1" 500 - INFO:root:zipimporter('/Users/Reiot/.virtualenvs/django_appengine/lib/python2.5/site-packages/setuptools-0.6c11-py2.5.egg', '') INFO:root:zipimporter('/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/setuptools-0.6c9-py2.5.egg', '') F........................................................... ====================================================================== FAIL: a request to the default page works in the dev_appserver ---------------------------------------------------------------------- Traceback (most recent call last): File "/Volumes/data/Documents/warclouds/appengine_django/tests/integration_test.py", line 176, in testBasic self.assertEquals(rv.status_code, 200) AssertionError: 500 != 200 I also tried with console import but it was ok. > which python /Users/Reiot/.virtualenvs/django_appengine/bin/python > python >>> import unittest Here is my environments: $ mkvirtualenv --no-site-packages no-django $ mkvirtualenv --no-site-packages django-1.1 $ mkvirtualenv --no-site-packages django-1.1.1 (django-1.1)$ easy_install Django-1.1.tar (django-1.1.1)$ easy_install Django-1.1.1.tar $ mkdir google-app-engine-django-svn $ cp -r google-app-engine-django-svn google-app-engine-django-svn-django-1.1 // copy appropriate django.zip $ cp -r google-app-engine-django-svn google-app-engine-django-svn-django-1.1.1 // copy appropriate django.zip

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Simple C# CSV Excel export class

- by Chris

Thought this might be handy for someone, this is an extremely simple CSV export class that I needed. Features: Extremely simple to use Escapes commas and quotes so excel handles them fine Exports date and datetimes in timezone-proof format Without further ado: using System; using System.Data.SqlTypes; using System.IO; using System.Text; using System.Collections.Generic; /// <summary> /// Simple CSV export /// Example: /// CsvExport myExport = new CsvExport(); /// /// myExport.AddRow(); /// myExport["Region"] = "New York, USA"; /// myExport["Sales"] = 100000; /// myExport["Date Opened"] = new DateTime(2003, 12, 31); /// /// myExport.AddRow(); /// myExport["Region"] = "Sydney \"in\" Australia"; /// myExport["Sales"] = 50000; /// myExport["Date Opened"] = new DateTime(2005, 1, 1, 9, 30, 0); /// /// Then you can do any of the following three output options: /// string myCsv = myExport.Export(); /// myExport.ExportToFile("Somefile.csv"); /// byte[] myCsvData = myExport.ExportToBytes(); /// </summary> public class CsvExport { /// <summary> /// To keep the ordered list of column names /// </summary> List<string> fields = new List<string>(); /// <summary> /// The list of rows /// </summary> List<Dictionary<string, object>> rows = new List<Dictionary<string, object>>(); /// <summary> /// The current row /// </summary> Dictionary<string, object> currentRow { get { return rows[rows.Count - 1]; } } /// <summary> /// Set a value on this column /// </summary> public object this[string field] { set { // Keep track of the field names, because the dictionary loses the ordering if (!fields.Contains(field)) fields.Add(field); currentRow[field] = value; } } /// <summary> /// Call this before setting any fields on a row /// </summary> public void AddRow() { rows.Add(new Dictionary<string, object>()); } /// <summary> /// Converts a value to how it should output in a csv file /// If it has a comma, it needs surrounding with double quotes /// Eg Sydney, Australia -> "Sydney, Australia" /// Also if it contains any double quotes ("), then they need to be replaced with quad quotes[sic] ("") /// Eg "Dangerous Dan" McGrew -> """Dangerous Dan"" McGrew" /// </summary> string MakeValueCsvFriendly(object value) { if (value == null) return ""; if (value is INullable && ((INullable)value).IsNull) return ""; if (value is DateTime) { if (((DateTime)value).TimeOfDay.TotalSeconds==0) return ((DateTime)value).ToString("yyyy-MM-dd"); return ((DateTime)value).ToString("yyyy-MM-dd HH:mm:ss"); } string output = value.ToString(); if (output.Contains(",") || output.Contains("\"")) output = '"' + output.Replace("\"", "\"\"") + '"'; return output; } /// <summary> /// Output all rows as a CSV returning a string /// </summary> public string Export() { StringBuilder sb = new StringBuilder(); // The header foreach (string field in fields) sb.Append(field).Append(","); sb.AppendLine(); // The rows foreach (Dictionary<string, object> row in rows) { foreach (string field in fields) sb.Append(MakeValueCsvFriendly(row[field])).Append(","); sb.AppendLine(); } return sb.ToString(); } /// <summary> /// Exports to a file /// </summary> public void ExportToFile(string path) { File.WriteAllText(path, Export()); } /// <summary> /// Exports as raw UTF8 bytes /// </summary> public byte[] ExportToBytes() { return Encoding.UTF8.GetBytes(Export()); } }

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MySQL "ERROR 1005 (HY000): Can't create table 'foo.#sql-12c_4' (errno: 150)"

- by Ankur Banerjee

Hi, I was working on creating some tables in database foo, but every time I end up with errno 150 regarding the foreign key. Firstly, here's my code for creating tables: CREATE TABLE Clients ( client_id CHAR(10) NOT NULL , client_name CHAR(50) NOT NULL , provisional_license_num CHAR(50) NOT NULL , client_address CHAR(50) NULL , client_city CHAR(50) NULL , client_county CHAR(50) NULL , client_zip CHAR(10) NULL , client_phone INT NULL , client_email CHAR(255) NULL , client_dob DATETIME NULL , test_attempts INT NULL ); CREATE TABLE Applications ( application_id CHAR(10) NOT NULL , office_id INT NOT NULL , client_id CHAR(10) NOT NULL , instructor_id CHAR(10) NOT NULL , car_id CHAR(10) NOT NULL , application_date DATETIME NULL ); CREATE TABLE Instructors ( instructor_id CHAR(10) NOT NULL , office_id INT NOT NULL , instructor_name CHAR(50) NOT NULL , instructor_address CHAR(50) NULL , instructor_city CHAR(50) NULL , instructor_county CHAR(50) NULL , instructor_zip CHAR(10) NULL , instructor_phone INT NULL , instructor_email CHAR(255) NULL , instructor_dob DATETIME NULL , lessons_given INT NULL ); CREATE TABLE Cars ( car_id CHAR(10) NOT NULL , office_id INT NOT NULL , engine_serial_num CHAR(10) NULL , registration_num CHAR(10) NULL , car_make CHAR(50) NULL , car_model CHAR(50) NULL ); CREATE TABLE Offices ( office_id INT NOT NULL , office_address CHAR(50) NULL , office_city CHAR(50) NULL , office_County CHAR(50) NULL , office_zip CHAR(10) NULL , office_phone INT NULL , office_email CHAR(255) NULL ); CREATE TABLE Lessons ( lesson_num INT NOT NULL , client_id CHAR(10) NOT NULL , date DATETIME NOT NULL , time DATETIME NOT NULL , milegage_used DECIMAL(5, 2) NULL , progress CHAR(50) NULL ); CREATE TABLE DrivingTests ( test_num INT NOT NULL , client_id CHAR(10) NOT NULL , test_date DATETIME NOT NULL , seat_num INT NOT NULL , score INT NULL , test_notes CHAR(255) NULL ); ALTER TABLE Clients ADD PRIMARY KEY (client_id); ALTER TABLE Applications ADD PRIMARY KEY (application_id); ALTER TABLE Instructors ADD PRIMARY KEY (instructor_id); ALTER TABLE Offices ADD PRIMARY KEY (office_id); ALTER TABLE Lessons ADD PRIMARY KEY (lesson_num); ALTER TABLE DrivingTests ADD PRIMARY KEY (test_num); ALTER TABLE Applications ADD CONSTRAINT FK_Applications_Offices FOREIGN KEY (office_id) REFERENCES Offices (office_id); ALTER TABLE Applications ADD CONSTRAINT FK_Applications_Clients FOREIGN KEY (client_id) REFERENCES Clients (client_id); ALTER TABLE Applications ADD CONSTRAINT FK_Applications_Instructors FOREIGN KEY (instructor_id) REFERENCES Instructors (instructor_id); ALTER TABLE Applications ADD CONSTRAINT FK_Applications_Cars FOREIGN KEY (car_id) REFERENCES Cars (car_id); ALTER TABLE Lessons ADD CONSTRAINT FK_Lessons_Clients FOREIGN KEY (client_id) REFERENCES Clients (client_id); ALTER TABLE Cars ADD CONSTRAINT FK_Cars_Offices FOREIGN KEY (office_id) REFERENCES Offices (office_id); ALTER TABLE Clients ADD CONSTRAINT FK_DrivingTests_Clients FOREIGN KEY (client_id) REFERENCES Clients (client_id); These are the errors that I get: mysql> ALTER TABLE Applications ADD CONSTRAINT FK_Applications_Cars FOREIGN KEY (car_id) REFERENCES Cars (car_id); ERROR 1005 (HY000): Can't create table 'foo.#sql-12c_4' (errno: 150) I ran SHOW ENGINE INNODB STATUS which gives a more detailed error description: ------------------------ LATEST FOREIGN KEY ERROR ------------------------ 100509 20:59:49 Error in foreign key constraint of table practice9/#sql-12c_4: FOREIGN KEY (car_id) REFERENCES Cars (car_id): Cannot find an index in the referenced table where the referenced columns appear as the first columns, or column types in the table and the referenced table do not match for constraint. Note that the internal storage type of ENUM and SET changed in tables created with >= InnoDB-4.1.12, and such columns in old tables cannot be referenced by such columns in new tables. See http://dev.mysql.com/doc/refman/5.1/en/innodb-foreign-key-constraints.html for correct foreign key definition. ------------ I searched around on StackOverflow and elsewhere online - came across a helpful blog post here with pointers on how to resolve this error - but I can't figure out what's going wrong. Any help would be appreciated!

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Add note model in Rails

- by dannymcc

Hi Everyone, I am following the 15 minute blog tutorial on Ruby on Rails .com: http://media.rubyonrails.org/video/rails_blog_2.mov and am stumbling into some issues. I am using the following alterations to the names in the tutorial: posts = kases comments = notes I have setup the models as follows: class Kase < ActiveRecord::Base validates_presence_of :jobno has_many :notes belongs_to :company # foreign key: company_id belongs_to :person # foreign key in join table belongs_to :surveyor, :class_name => "Company", :foreign_key => "appointedsurveyor_id" belongs_to :surveyorperson, :class_name => "Person", :foreign_key => "surveyorperson_id" def to_param jobno end and... class Note < ActiveRecord::Base belongs_to :kase end The Notes controller look like this: # POST /notes # POST /notes.xml def create @kase = Kase.find(params[:kase_id]) @note = @kase.notes.build(params[:note]) redirect_to @kase end and the database scheme for Kases looks like this: create_table "notes", :force => true do |t| t.integer "kase_id" t.text "body" t.datetime "created_at" t.datetime "updated_at" end and for kases... create_table "kases", :force => true do |t| t.string "jobno" t.date "dateinstructed" t.string "clientref" t.string "clientcompanyname" t.text "clientcompanyaddress" t.string "clientcompanyfax" t.string "casehandlername" t.string "casehandlertel" t.string "casehandleremail" t.text "casesubject" t.string "transport" t.string "goods" t.string "claimantname" t.string "claimantaddressline1" t.string "claimantaddressline2" t.string "claimantaddressline3" t.string "claimantaddresscity" t.string "claimantaddresspostcode" t.string "claimantcontact" t.string "claimanttel" t.string "claimantmob" t.string "claimantemail" t.string "claimanturl" t.string "lyingatlocationname" t.string "lyingatlocationaddressline1" t.string "lyingatlocationaddressline2" t.string "lyingatlocationaddressline3" t.string "lyingatlocationaddresscity" t.string "lyingatlocationaddresspostcode" t.string "lyingatlocationcontactname" t.string "lyingattel" t.string "lyingatmobile" t.string "lyingatlocationurl" t.text "comments" t.string "invoicenumber" t.string "netamount" t.string "vat" t.string "grossamount" t.date "dateclosed" t.date "datepaid" t.datetime "filecreated" t.string "avatar_file_name" t.string "avatar_content_type" t.integer "avatar_file_size" t.datetime "avatar_updated_at" t.datetime "created_at" t.datetime "updated_at" t.string "kase_status" t.string "invoice_date" t.integer "surveyorperson_id" t.integer "appointedsurveyor_id" t.integer "person_id" t.string "company_id" t.string "dischargeamount" t.string "dishchargeheader" t.text "highrisesubject" end Whenever I enter a note into the kase show view's note entry form: <h2>Notes</h2> <div id="sub-notes"> <%= render :partial => @kase.notes %> </div> <% form_for [@kase, Note.new] do |f| %> <p> <%= f.label :body, "New Note" %><br /> <%= f.text_area :body %> </p> <p><%= f.submit "Add Note" %></p> <% end %> partial: <% div_for note do %> <p> <strong>Created <%= time_ago_in_words(note.created_at) %> ago</strong><br /> <%= h(note.body) %> </p> <% end %> I get the following error: ActiveRecord::RecordNotFound in NotesController#create Couldn't find Kase with ID=Test Case I have tried removing the def to_param jobno end from the kase model, but the same error shows. Any ideas what I'm missing? Thanks, Danny

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wpf exit thread automatically when application closes

- by toni

Hi, I have a main wpf window and one of its controls is a user control that I have created. this user control is an analog clock and contains a thread that update hour, minute and second hands. Initially it wasn't a thread, it was a timer event that updated the hour, minutes and seconds but I have changed it to a thread because the application do some hard work when the user press a start button and then the clock don't update so I changed it to a thread. COde snippet of wpf window: <Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:GParts" xmlns:Microsoft_Windows_Themes="clr-namespace:Microsoft.Windows.Themes assembly=PresentationFramework.Aero" xmlns:UC="clr-namespace:GParts.UserControls" x:Class="GParts.WinMain" Title="GParts" WindowState="Maximized" Closing="Window_Closing" Icon="/Resources/Calendar-clock.png" x:Name="WMain" > <...>  <UC:AnalogClock Grid.Row="1" x:Name="AnalogClock" Background="Transparent" Margin="0" Height="Auto" Width="Auto"/> <...> </Window> My problem is when the user exits the application then the thread seems to continue executing. I would like the thread finishes automatically when main windows closes. code snippet of user control constructor: namespace GParts.UserControls { /// <summary> /// Lógica de interacción para AnalogClock.xaml /// </summary> public partial class AnalogClock : UserControl { System.Timers.Timer timer = new System.Timers.Timer(1000); public AnalogClock() { InitializeComponent(); MDCalendar mdCalendar = new MDCalendar(); DateTime date = DateTime.Now; TimeZone time = TimeZone.CurrentTimeZone; TimeSpan difference = time.GetUtcOffset(date); uint currentTime = mdCalendar.Time() + (uint)difference.TotalSeconds; christianityCalendar.Content = mdCalendar.Date("d/e/Z", currentTime, false); // this was before implementing thread //timer.Elapsed += new System.Timers.ElapsedEventHandler(timer_Elapsed); //timer.Enabled = true; // The Work to perform ThreadStart start = delegate() { // With this condition the thread exits when main window closes but // despite of this it seems like the thread continues executing after // exiting application because in task manager cpu is very busy // while ((this.IsInitialized) && (this.Dispatcher.HasShutdownFinished== false)) { this.Dispatcher.Invoke(DispatcherPriority.Normal, (Action)(() => { DateTime hora = DateTime.Now; secondHand.Angle = hora.Second * 6; minuteHand.Angle = hora.Minute * 6; hourHand.Angle = (hora.Hour * 30) + (hora.Minute * 0.5); DigitalClock.CurrentTime = hora; })); } Console.Write("Quit ok"); }; // Create the thread and kick it started! new Thread(start).Start(); } // this was before implementing thread void timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e) { this.Dispatcher.Invoke(DispatcherPriority.Normal, (Action)(() => { DateTime hora = DateTime.Now; secondHand.Angle = hora.Second * 6; minuteHand.Angle = hora.Minute * 6; hourHand.Angle = (hora.Hour * 30) + (hora.Minute * 0.5); DigitalClock.CurrentTime = hora; })); } } // end class } // end namespace How can I exit correctly from thread automatically when main window closes and then application exits? Thanks very much!

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OpenXML sdk Modify a sheet in my Excel document

- by user465202

hi! I create an empty template in excel. I would like to open the template and edit the document but I do not know how to change the existing sheet. That's the code: using (SpreadsheetDocument xl = SpreadsheetDocument.Open(filename, true)) { WorkbookPart wbp = xl.WorkbookPart; WorkbookPart workbook = xl.WorkbookPart; // Get the worksheet with the required name. // To be used to match the ID for the required sheet data // because the Sheet class and the SheetData class aren't // linked to each other directly. Sheet s = null; if (wbp.Workbook.Sheets.Elements().Count(nm = nm.Name == sheetName) == 0) { // no such sheet with that name xl.Close(); return; } else { s = (Sheet)wbp.Workbook.Sheets.Elements().Where(nm = nm.Name == sheetName).First(); } WorksheetPart wsp = (WorksheetPart)xl.WorkbookPart.GetPartById(s.Id.Value); Worksheet worksheet = new Worksheet(); SheetData sd = new SheetData(); //SheetData sd = (SheetData)wsp.Worksheet.GetFirstChild(); Stylesheet styleSheet = workbook.WorkbookStylesPart.Stylesheet; //SheetData sheetData = new SheetData(); //build the formatted header style UInt32Value headerFontIndex = util.CreateFont( styleSheet, "Arial", 10, true, System.Drawing.Color.Red); //build the formatted date style UInt32Value dateFontIndex = util.CreateFont( styleSheet, "Arial", 8, true, System.Drawing.Color.Black); //set the background color style UInt32Value headerFillIndex = util.CreateFill( styleSheet, System.Drawing.Color.Black); //create the cell style by combining font/background UInt32Value headerStyleIndex = util.CreateCellFormat( styleSheet, headerFontIndex, headerFillIndex, null); /* * Create a set of basic cell styles for specific formats... * If you are controlling your table then you can simply create the styles you need, * this set of code is still intended to be generic. */ _numberStyleId = util.CreateCellFormat(styleSheet, null, null, UInt32Value.FromUInt32(3)); _doubleStyleId = util.CreateCellFormat(styleSheet, null, null, UInt32Value.FromUInt32(4)); _dateStyleId = util.CreateCellFormat(styleSheet, null, null, UInt32Value.FromUInt32(14)); _textStyleId = util.CreateCellFormat(styleSheet, headerFontIndex, headerFillIndex, null); _percentageStyleId = util.CreateCellFormat(styleSheet, null, null, UInt32Value.FromUInt32(9)); util.AddNumber(xl, sheetName, (UInt32)3, "E", "27", _numberStyleId); util.AddNumber(xl, sheetName, (UInt32)3, "F", "3.6", _doubleStyleId); util.AddNumber(xl, sheetName, (UInt32)5, "L", "5", _percentageStyleId); util.AddText(xl, sheetName, (UInt32)5, "M", "Dario", _textStyleId); util.AddDate(xl, sheetName, (UInt32)3, "J", DateTime.Now, _dateStyleId); util.AddImage(xl, sheetName, imagePath, "Smile", "Smile", 30, 30); util.MergeCells(xl, sheetName, "D12", "F12"); //util.DeleteValueCell(spreadsheet, sheetName, "F", (UInt32)8); txtCellText.Text = util.GetCellValue(xl, sheetName, (UInt32)5, "M"); double number = util.GetCellDoubleValue(xl, sheetName, (UInt32)3, "E"); double numberD = util.GetCellDoubleValue(xl, sheetName, (UInt32)3, "F"); DateTime datee = util.GetCellDateTimeValue(xl, sheetName, (UInt32)3, "J"); //txtDoubleCell.Text = util.GetCellValue(spreadsheet, sheetName, (UInt32)3, "P"); txtPercentualeCell.Text = util.GetCellValue(xl, sheetName, (UInt32)5, "L"); string date = util.GetCellValue(xl, sheetName, (UInt32)3, "J"); double dateD = Convert.ToDouble(date); DateTime dateTime = DateTime.FromOADate(dateD); txtDateCell.Text = dateTime.ToShortDateString(); //worksheet.Append(sd); /* Columns columns = new Columns(); columns.Append(util.CreateColumnData(10, 10, 40)); worksheet.Append(columns); */ SheetProtection sheetProtection1 = new SheetProtection() { Sheet = true, Objects = true, Scenarios = true, SelectLockedCells = true, SelectUnlockedCells = true }; worksheet.Append(sheetProtection1); wsp.Worksheet = worksheet; wsp.Worksheet.Save(); xl.WorkbookPart.Workbook.Save(); xl.Close(); thanks!

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System.Threading.Timer Doesn't Trigger my TimerCallBack Delegate

- by Tom Kong

Hi, I am writing my first Windows Service using C# and I am having some trouble with my Timer class. When the service is started, it runs as expected but the code will not execute again (I want it to run every minute) Please take a quick look at the attached source and let me know if you see any obvious mistakes! TIA using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Diagnostics; using System.Linq; using System.ServiceProcess; using System.Text; using System.Threading; using System.IO; namespace CXO001 { public partial class Service1 : ServiceBase { public Service1() { InitializeComponent(); } /* * Aim: To calculate and update the Occupancy values for the different Sites * * Method: Retrieve data every minute, updating a public value which can be polled */ protected override void OnStart(string[] args) { Daemon(); } public void Daemon() { TimerCallback tcb = new TimerCallback(On_Tick); TimeSpan duetime = new TimeSpan(0, 0, 1); TimeSpan interval = new TimeSpan(0, 1, 0); Timer querytimer = new Timer(tcb, null, duetime, interval); } protected override void OnStop() { } static int[] floorplanids = new int[] { 115, 114, 107, 108 }; public static List<Record> Records = new List<Record>(); static bool firstrun = true; public static void On_Tick(object timercallback) { //Update occupancy data for the last minute //Save a copy of the public values to HDD with a timestamp string starttime; if (Records.Count > 0) { starttime = Records.Last().TS; firstrun = false; } else { starttime = DateTime.Today.AddHours(7).ToString(); firstrun = true; } DateTime endtime = DateTime.Now; GetData(starttime, endtime); } public static void GetData(string starttime, DateTime endtime) { string connstr = "Data Source = 192.168.1.123; Initial Catalog = Brickstream_OPS; User Id = Brickstream; Password = bstas;"; DataSet resultds = new DataSet(); //Get the occupancy for each Zone foreach (int zone in floorplanids) { SQL s = new SQL(); string querystr = "SELECT SUM(DIRECTIONAL_METRIC.NUM_TO_ENTER - DIRECTIONAL_METRIC.NUM_TO_EXIT) AS 'Occupancy' FROM REPORT_OBJECT INNER JOIN REPORT_OBJ_METRIC ON REPORT_OBJECT.REPORT_OBJ_ID = REPORT_OBJ_METRIC.REPORT_OBJECT_ID INNER JOIN DIRECTIONAL_METRIC ON REPORT_OBJ_METRIC.REP_OBJ_METRIC_ID = DIRECTIONAL_METRIC.REP_OBJ_METRIC_ID WHERE (REPORT_OBJ_METRIC.M_START_TIME BETWEEN '" + starttime + "' AND '" + endtime.ToString() + "') AND (REPORT_OBJECT.FLOORPLAN_ID = '" + zone + "');"; resultds = s.Go(querystr, connstr, zone.ToString(), resultds); } List<Record> result = new List<Record>(); int c = 0; foreach (DataTable dt in resultds.Tables) { Record r = new Record(); r.TS = DateTime.Now.ToString(); r.Zone = dt.TableName; if (!firstrun) { r.Occupancy = (dt.Rows[0].Field<int>("Occupancy")) + (Records[c].Occupancy); } else { r.Occupancy = dt.Rows[0].Field<int>("Occupancy"); } result.Add(r); c++; } Records = result; MrWriter(); } public static void MrWriter() { StringBuilder output = new StringBuilder("Time,Zone,Occupancy\n"); foreach (Record r in Records) { output.Append(r.TS); output.Append(","); output.Append(r.Zone); output.Append(","); output.Append(r.Occupancy.ToString()); output.Append("\n"); } output.Append(firstrun.ToString()); output.Append(DateTime.Now.ToFileTime()); string filePath = @"C:\temp\CXO.csv"; File.WriteAllText(filePath, output.ToString()); } } }

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Parallelism in .NET – Part 3, Imperative Data Parallelism: Early Termination

- by Reed

Although simple data parallelism allows us to easily parallelize many of our iteration statements, there are cases that it does not handle well. In my previous discussion, I focused on data parallelism with no shared state, and where every element is being processed exactly the same. Unfortunately, there are many common cases where this does not happen. If we are dealing with a loop that requires early termination, extra care is required when parallelizing. Often, while processing in a loop, once a certain condition is met, it is no longer necessary to continue processing. This may be a matter of finding a specific element within the collection, or reaching some error case. The important distinction here is that, it is often impossible to know until runtime, what set of elements needs to be processed. In my initial discussion of data parallelism, I mentioned that this technique is a candidate when you can decompose the problem based on the data involved, and you wish to apply a single operation concurrently on all of the elements of a collection. This covers many of the potential cases, but sometimes, after processing some of the elements, we need to stop processing. As an example, lets go back to our previous Parallel.ForEach example with contacting a customer. However, this time, we’ll change the requirements slightly. In this case, we’ll add an extra condition – if the store is unable to email the customer, we will exit gracefully. The thinking here, of course, is that if the store is currently unable to email, the next time this operation runs, it will handle the same situation, so we can just skip our processing entirely. The original, serial case, with this extra condition, might look something like the following: foreach(var customer in customers) { // Run some process that takes some time... DateTime lastContact = theStore.GetLastContact(customer); TimeSpan timeSinceContact = DateTime.Now - lastContact; // If it's been more than two weeks, send an email, and update... if (timeSinceContact.Days > 14) { // Exit gracefully if we fail to email, since this // entire process can be repeated later without issue. if (theStore.EmailCustomer(customer) == false) break; customer.LastEmailContact = DateTime.Now; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, we’re processing our loop, but at any point, if we fail to send our email successfully, we just abandon this process, and assume that it will get handled correctly the next time our routine is run. If we try to parallelize this using Parallel.ForEach, as we did previously, we’ll run into an error almost immediately: the break statement we’re using is only valid when enclosed within an iteration statement, such as foreach. When we switch to Parallel.ForEach, we’re no longer within an iteration statement – we’re a delegate running in a method. This needs to be handled slightly differently when parallelized. Instead of using the break statement, we need to utilize a new class in the Task Parallel Library: ParallelLoopState. The ParallelLoopState class is intended to allow concurrently running loop bodies a way to interact with each other, and provides us with a way to break out of a loop. In order to use this, we will use a different overload of Parallel.ForEach which takes an IEnumerable<T> and an Action<T, ParallelLoopState> instead of an Action<T>. Using this, we can parallelize the above operation by doing: Parallel.ForEach(customers, (customer, parallelLoopState) => { // Run some process that takes some time... DateTime lastContact = theStore.GetLastContact(customer); TimeSpan timeSinceContact = DateTime.Now - lastContact; // If it's been more than two weeks, send an email, and update... if (timeSinceContact.Days > 14) { // Exit gracefully if we fail to email, since this // entire process can be repeated later without issue. if (theStore.EmailCustomer(customer) == false) parallelLoopState.Break(); else customer.LastEmailContact = DateTime.Now; } }); There are a couple of important points here. First, we didn’t actually instantiate the ParallelLoopState instance. It was provided directly to us via the Parallel class. All we needed to do was change our lambda expression to reflect that we want to use the loop state, and the Parallel class creates an instance for our use. We also needed to change our logic slightly when we call Break(). Since Break() doesn’t stop the program flow within our block, we needed to add an else case to only set the property in customer when we succeeded. This same technique can be used to break out of a Parallel.For loop. That being said, there is a huge difference between using ParallelLoopState to cause early termination and to use break in a standard iteration statement. When dealing with a loop serially, break will immediately terminate the processing within the closest enclosing loop statement. Calling ParallelLoopState.Break(), however, has a very different behavior. The issue is that, now, we’re no longer processing one element at a time. If we break in one of our threads, there are other threads that will likely still be executing. This leads to an important observation about termination of parallel code: Early termination in parallel routines is not immediate. Code will continue to run after you request a termination. This may seem problematic at first, but it is something you just need to keep in mind while designing your routine. ParallelLoopState.Break() should be thought of as a request. We are telling the runtime that no elements that were in the collection past the element we’re currently processing need to be processed, and leaving it up to the runtime to decide how to handle this as gracefully as possible. Although this may seem problematic at first, it is a good thing. If the runtime tried to immediately stop processing, many of our elements would be partially processed. It would be like putting a return statement in a random location throughout our loop body – which could have horrific consequences to our code’s maintainability. In order to understand and effectively write parallel routines, we, as developers, need a subtle, but profound shift in our thinking. We can no longer think in terms of sequential processes, but rather need to think in terms of requests to the system that may be handled differently than we’d first expect. This is more natural to developers who have dealt with asynchronous models previously, but is an important distinction when moving to concurrent programming models. As an example, I’ll discuss the Break() method. ParallelLoopState.Break() functions in a way that may be unexpected at first. When you call Break() from a loop body, the runtime will continue to process all elements of the collection that were found prior to the element that was being processed when the Break() method was called. This is done to keep the behavior of the Break() method as close to the behavior of the break statement as possible. We can see the behavior in this simple code: var collection = Enumerable.Range(0, 20); var pResult = Parallel.ForEach(collection, (element, state) => { if (element > 10) { Console.WriteLine("Breaking on {0}", element); state.Break(); } Console.WriteLine(element); }); If we run this, we get a result that may seem unexpected at first: 0 2 1 5 6 3 4 10 Breaking on 11 11 Breaking on 12 12 9 Breaking on 13 13 7 8 Breaking on 15 15 What is occurring here is that we loop until we find the first element where the element is greater than 10. In this case, this was found, the first time, when one of our threads reached element 11. It requested that the loop stop by calling Break() at this point. However, the loop continued processing until all of the elements less than 11 were completed, then terminated. This means that it will guarantee that elements 9, 7, and 8 are completed before it stops processing. You can see our other threads that were running each tried to break as well, but since Break() was called on the element with a value of 11, it decides which elements (0-10) must be processed. If this behavior is not desirable, there is another option. Instead of calling ParallelLoopState.Break(), you can call ParallelLoopState.Stop(). The Stop() method requests that the runtime terminate as soon as possible , without guaranteeing that any other elements are processed. Stop() will not stop the processing within an element, so elements already being processed will continue to be processed. It will prevent new elements, even ones found earlier in the collection, from being processed. Also, when Stop() is called, the ParallelLoopState’s IsStopped property will return true. This lets longer running processes poll for this value, and return after performing any necessary cleanup. The basic rule of thumb for choosing between Break() and Stop() is the following. Use ParallelLoopState.Stop() when possible, since it terminates more quickly. This is particularly useful in situations where you are searching for an element or a condition in the collection. Once you’ve found it, you do not need to do any other processing, so Stop() is more appropriate. Use ParallelLoopState.Break() if you need to more closely match the behavior of the C# break statement. Both methods behave differently than our C# break statement. Unfortunately, when parallelizing a routine, more thought and care needs to be put into every aspect of your routine than you may otherwise expect. This is due to my second observation: Parallelizing a routine will almost always change its behavior. This sounds crazy at first, but it’s a concept that’s so simple its easy to forget. We’re purposely telling the system to process more than one thing at the same time, which means that the sequence in which things get processed is no longer deterministic. It is easy to change the behavior of your routine in very subtle ways by introducing parallelism. Often, the changes are not avoidable, even if they don’t have any adverse side effects. This leads to my final observation for this post: Parallelization is something that should be handled with care and forethought, added by design, and not just introduced casually.

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Parallelism in .NET – Part 2, Simple Imperative Data Parallelism

- by Reed

In my discussion of Decomposition of the problem space, I mentioned that Data Decomposition is often the simplest abstraction to use when trying to parallelize a routine. If a problem can be decomposed based off the data, we will often want to use what MSDN refers to as Data Parallelism as our strategy for implementing our routine. The Task Parallel Library in .NET 4 makes implementing Data Parallelism, for most cases, very simple. Data Parallelism is the main technique we use to parallelize a routine which can be decomposed based off data. Data Parallelism refers to taking a single collection of data, and having a single operation be performed concurrently on elements in the collection. One side note here: Data Parallelism is also sometimes referred to as the Loop Parallelism Pattern or Loop-level Parallelism. In general, for this series, I will try to use the terminology used in the MSDN Documentation for the Task Parallel Library. This should make it easier to investigate these topics in more detail. Once we’ve determined we have a problem that, potentially, can be decomposed based on data, implementation using Data Parallelism in the TPL is quite simple. Let’s take our example from the Data Decomposition discussion – a simple contrast stretching filter. Here, we have a collection of data (pixels), and we need to run a simple operation on each element of the pixel. Once we know the minimum and maximum values, we most likely would have some simple code like the following: for (int row=0; row < pixelData.GetUpperBound(0); ++row) { for (int col=0; col < pixelData.GetUpperBound(1); ++col) { pixelData[row, col] = AdjustContrast(pixelData[row, col], minPixel, maxPixel); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This simple routine loops through a two dimensional array of pixelData, and calls the AdjustContrast routine on each pixel. As I mentioned, when you’re decomposing a problem space, most iteration statements are potentially candidates for data decomposition. Here, we’re using two for loops – one looping through rows in the image, and a second nested loop iterating through the columns. We then perform one, independent operation on each element based on those loop positions. This is a prime candidate – we have no shared data, no dependencies on anything but the pixel which we want to change. Since we’re using a for loop, we can easily parallelize this using the Parallel.For method in the TPL: Parallel.For(0, pixelData.GetUpperBound(0), row => { for (int col=0; col < pixelData.GetUpperBound(1); ++col) { pixelData[row, col] = AdjustContrast(pixelData[row, col], minPixel, maxPixel); } }); Here, by simply changing our first for loop to a call to Parallel.For, we can parallelize this portion of our routine. Parallel.For works, as do many methods in the TPL, by creating a delegate and using it as an argument to a method. In this case, our for loop iteration block becomes a delegate creating via a lambda expression. This lets you write code that, superficially, looks similar to the familiar for loop, but functions quite differently at runtime. We could easily do this to our second for loop as well, but that may not be a good idea. There is a balance to be struck when writing parallel code. We want to have enough work items to keep all of our processors busy, but the more we partition our data, the more overhead we introduce. In this case, we have an image of data – most likely hundreds of pixels in both dimensions. By just parallelizing our first loop, each row of pixels can be run as a single task. With hundreds of rows of data, we are providing fine enough granularity to keep all of our processors busy. If we parallelize both loops, we’re potentially creating millions of independent tasks. This introduces extra overhead with no extra gain, and will actually reduce our overall performance. This leads to my first guideline when writing parallel code: Partition your problem into enough tasks to keep each processor busy throughout the operation, but not more than necessary to keep each processor busy. Also note that I parallelized the outer loop. I could have just as easily partitioned the inner loop. However, partitioning the inner loop would have led to many more discrete work items, each with a smaller amount of work (operate on one pixel instead of one row of pixels). My second guideline when writing parallel code reflects this: Partition your problem in a way to place the most work possible into each task. This typically means, in practice, that you will want to parallelize the routine at the “highest” point possible in the routine, typically the outermost loop. If you’re looking at parallelizing methods which call other methods, you’ll want to try to partition your work high up in the stack – as you get into lower level methods, the performance impact of parallelizing your routines may not overcome the overhead introduced. Parallel.For works great for situations where we know the number of elements we’re going to process in advance. If we’re iterating through an IList<T> or an array, this is a typical approach. However, there are other iteration statements common in C#. In many situations, we’ll use foreach instead of a for loop. This can be more understandable and easier to read, but also has the advantage of working with collections which only implement IEnumerable<T>, where we do not know the number of elements involved in advance. As an example, lets take the following situation. Say we have a collection of Customers, and we want to iterate through each customer, check some information about the customer, and if a certain case is met, send an email to the customer and update our instance to reflect this change. Normally, this might look something like: foreach(var customer in customers) { // Run some process that takes some time... DateTime lastContact = theStore.GetLastContact(customer); TimeSpan timeSinceContact = DateTime.Now - lastContact; // If it's been more than two weeks, send an email, and update... if (timeSinceContact.Days > 14) { theStore.EmailCustomer(customer); customer.LastEmailContact = DateTime.Now; } } Here, we’re doing a fair amount of work for each customer in our collection, but we don’t know how many customers exist. If we assume that theStore.GetLastContact(customer) and theStore.EmailCustomer(customer) are both side-effect free, thread safe operations, we could parallelize this using Parallel.ForEach: Parallel.ForEach(customers, customer => { // Run some process that takes some time... DateTime lastContact = theStore.GetLastContact(customer); TimeSpan timeSinceContact = DateTime.Now - lastContact; // If it's been more than two weeks, send an email, and update... if (timeSinceContact.Days > 14) { theStore.EmailCustomer(customer); customer.LastEmailContact = DateTime.Now; } }); Just like Parallel.For, we rework our loop into a method call accepting a delegate created via a lambda expression. This keeps our new code very similar to our original iteration statement, however, this will now execute in parallel. The same guidelines apply with Parallel.ForEach as with Parallel.For. The other iteration statements, do and while, do not have direct equivalents in the Task Parallel Library. These, however, are very easy to implement using Parallel.ForEach and the yield keyword. Most applications can benefit from implementing some form of Data Parallelism. Iterating through collections and performing “work” is a very common pattern in nearly every application. When the problem can be decomposed by data, we often can parallelize the workload by merely changing foreach statements to Parallel.ForEach method calls, and for loops to Parallel.For method calls. Any time your program operates on a collection, and does a set of work on each item in the collection where that work is not dependent on other information, you very likely have an opportunity to parallelize your routine.

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HTML5 Semantics - H1 or H2 for ARTICLE titles in a SECTION

- by Matt

It's my understanding (based from this chapter of Dive into HTML5: http://goo.gl/9zliD) that it can be considered semantically appropriate to use H1 tags in multiple areas of the page, as a method of setting the most important title for that particular content. If I'm using this methodology, and I have a SECTION which I've assigned an H1 of 'Articles', should I use H1 or H2 to define the titles for ARTICLEs in that SECTION? This is a bit confusing to me as the article titles are the most important heading for their ARTICLE, but are also 'children' of the SECTION's title. Example code: <section class="article-list"> <header> <h1>Articles</h1> </header> <article> <header> <h2>Article Title</h2> <time datetime="201-02-01">Today</time> </header> <p>Article text...</p> </article> <article> <header> <h2>Article Title</h2> <time datetime="2011-01-31">Yesterday</time> </header> <p>Article text...</p> </article> <article> <header> <h2>Article Title</h2> <time datetime="2011-01-30">The Day Before Yesterday</time> </header> <p>Article text...</p> </article> </section>

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Formatting Dates, Times and Numbers in ASP.NET

Formatting is the process of converting a variable from its native type into a string representation. Anytime you display a DateTime or numeric variables in an ASP.NET page, you are formatting that variable from its native type into some sort of string representation. How a DateTime or numeric variable is formatted depends on the culture settings and the format string. Because dates and numeric values are formatted differently across cultures, the .NET Framework bases its formatting on the specified culture settings. By default, the formatting routines use the culture settings defined on the web server, but you can indicate that a particular culture be used anytime you format. In addition to the culture settings, formatting is also affected by a format string, which spells out the formatting details to apply. The .NET Framework contains a bounty of format strings. There are standard format strings, which are typically a single letter that applies detailed formatting logic. For example, the "C" format specifier will format a numeric type as a currency value; the "Y" format specifier displays the month name and four-digit year of the specified DateTime value. There are also custom format strings, which display a apply a very specific formatting rule. These custom format strings can be put together to build more intricate formats. For instance, the format string "dddd, MMMM d" displays the full day of the week name followed by a comma followed by the full name of the month followed by the day of the month. For more involved formatting scenarios, where neither the standard or custom format strings cut the mustard, you can always create your own formatting extension methods. This article explores the standard format strings for dates, times and numbers and includes a number of custom formatting methods I've created and use in my own projects. There's also a demo application you can download that lets you specify a culture and then shows you the output for the standard format strings for the selected culture. Read on to learn more! Read More >

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