ARSC T3E Users' Newsletter 183, Nov. 24, 1999

HPC Seminars at ARSC: Dec 7-8, Preliminary Schedule

Here is the preliminary schedule of speakers and talks:

Tuesday, Dec. 7

---

• 2:00 Seminar - "Managing Tape Based Archives"
  Gene Harano, National Center for Atmospheric Research,
  Boulder, CO
  

• 3:00 Seminar - "Computational Science and Engineering Research
  at the California Institute of Technology"
  Jim Poole
  

Wednesday, Dec. 8

---

• 2:00 Seminar - "The state of HPF, OpenMP and MPI"
  Prof. Barbara Chapman, U of Houston
  

• 3:00 Seminar - "Effective Parallel Programming in Advanced ZPL"
  Prof. Larry Snyder, U of Washington
  

Eurotools Request

Eurotools is at:

http://www.eurotools.org

Top500 List

• The top 3 systems are all part of the ASCI project, with ASCI Red just taking the top position from IBM and SGI ASCI Blue.
• In the top 20 it is a mixture of government laboratory work and weather/climate centers. Although Charles-Schwab makes an interesting entry at 12 in the 'Industry Finance' category.
• The top100 is mostly MPP systems and a number of bigger SMP clusters with a few of the bigger vectors keeping pace. Oak Ridge National Laboratory still gets a mention for the Intel XP/S-MP 150 3000 processor system at 70.
• The bottom parts of the list are full of various SMP systems supporting a diverse range of needs from industries such as eBay, various airlines, numerous banks and trading houses, and image rendering companies such as Industrial Light & Magic.

New Paper on PEMCS site: Communication and Scalability

http://hpc-journals.ecs.soton.ac.uk/PEMCS/Papers/

Comparing the Communication Performance and Scalability of a SGI Origin 2000, a Cluster of Origin 2000's and a Cray T3E-1200 using SHMEM and MPI Routines, Glenn R. Luecke, Bruno Raffin and James J. Coyle, Iowa State University, Ames, Iowa, USA, October, 1999.

A: {{ Can you write a program (C or Fortran) that prints the path, 
   {{ relative or absolute, to its executable?
   {{
   {{ It should work whether you type the path to the executable
   {{ explicitly or if you type its name, and the system must search the
   {{ PATH variable to locate it.  (In other words, argv[0] won't always
   {{ hold the answer.)

• Richard Griswold sent the only shell independent solution. If argv[0] doesn't contain the path, it searches all directories in the PATH environment variable for the executable.

• Brad Chamberlain's version uses argv[0], when it contains the path, and csh's "which" function, when it doesn't. (It could be extended to check the caller's shell, and use "whence" if found to be ksh.)

• Derek Bastille's version uses a nifty Korn shell feature. The ksh environment variable, "_", is set to the absolute or relative path of a command when it is executed (and re-used later for other things). Derek's version doesn't worry about argv[0] at all, but simply grabs "_".

Here are the solutions: Richard's:

#include <dirent.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <sys/types.h>
#include <unistd.h>

#define PATH_MAX 1024

int checkpath( char *path, char *exec ) {
  int            rc;   /* Return code for strlen and access      */
  char          *str;  /* Temporary string for access()          */
  DIR           *dir;  /* Dir struct for opendir() and readdir() */
  struct dirent *ent;  /* Dir entry struct from readdir()        */

  /* Find an executable file in path that has same name as exec */
  dir = opendir( path );
  while ( ( ent = readdir( dir ) ) != NULL )
    if ( strcmp( ent->d_name, exec ) == 0 ) {
      str = ( char * ) malloc( PATH_MAX * sizeof( char ) );
      rc  = strlen( path );
      strncpy( str, path, rc );
      str[rc] = '/'; str[rc+1] = '\0';
      rc = access( strcat( str, ent->d_name ), X_OK );
      free( str ); closedir( dir );
      return rc == 0 ? 1 : 0;
    }
  closedir( dir ); return 0;
}

void printrelative( char *path, char *exec ) {
  int   len,  /* Length of cwd             */
        i;    /* Index                     */
  char *cwd;  /* Current working directory */

  cwd = ( char * ) malloc( PATH_MAX * sizeof( char ) );
  cwd = getcwd( cwd, PATH_MAX );
  len = strlen( cwd );

  if ( strcmp( cwd, path ) == 0 ) {          /* Are cwd and path the same?  */
    path[0] = '.'; path[1] = '\0';
  } else if ( len < strlen( path ) ) {       /* Remove CWD from path        */
    for ( i = 0; i < len; i++ )
      if ( cwd[i] != path[i] ) break;
    if ( i == len )                          /* CWD is in beginning of path */
      if ( i == 1 ) { path = path + i;     } /* Fix up path if cwd == '/'   */
      else          { path = path + i + 1; }
  }
  printf( "\"%s\" is in directory: %s\n", exec, path );
  free( cwd  );
}

int main( int argc, char *argv[] ) {
  int   s,    /* Start of a path in PATH envvar */
        len,  /* Length of PATH envvar          */
        i;    /* Index                          */
  char *str;  /* PATH envvar or executable name */

  if ( ( str = rindex( argv[0], '/' ) ) != NULL ) {
    str[0] = '\0';
    printf( "\"%s\" is in directory: %s\n", str+1, argv[0] );
  } else {
    str = getenv( "PATH" ); len = strlen( str );
    for ( i = 0, s = 0; i < len; i++ )
      if ( str[i] == ':' ) {
        str[i] = '\0';
        if ( checkpath( str + s, argv[0] ) ) break;
        else                                 s = i + 1;
      }
    printrelative( str + s, argv[0] );
  }
  return 0;
}

// A few assumptions:
//
//  * /tmp/.findme.pathname can be written to
//  * path names will not be longer than 255 characters
//  * executable's name will not be longer than ~220 characters


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// someplace to store the output of a shell "which" command
static const char* const tmpfilename = "/tmp/.findme.pathname";

void main(int argc,char* argv[]) {
  char* lastslash;    // pointer to rightmost slash in string
  char* progname;     // pointer to program name
  char* pathname;     // pointer to path name
  char command[256];  // buffer for sprintf()ing commands
  FILE* infile;       // file pointer for reading shell "which" command output
  char fullpath[256]; // buffer for storing full path

  lastslash = strrchr(argv[0],'/');  // see if path is on argv[0]
  if (lastslash != NULL) {           // if so...
    *lastslash = '\0';               // cap string there
    progname = lastslash + 1;        // set pointers to filename, pathname
    pathname = argv[0];
  } else {
    progname = argv[0];              // else argv[0] holds program name

    sprintf(command,"which %s > %s",argv[0],tmpfilename); // setup a which
    system(command);                                      // & execute it

    infile = fopen(tmpfilename,"r");                      // read the output
    fscanf(infile,"%s",fullpath);
    fclose(infile);

    sprintf(command,"rm %s",tmpfilename);                 // remove tmp file
    system(command);

    pathname = fullpath;                                  // search for slash
    lastslash = strrchr(pathname,'/');                    // cap string
    *lastslash = '\0';
  }
  printf("\"%s\" is in directory: %s\n",progname,pathname);  // output results
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[]) {

/*
 * This code is ksh specific.  It works because ksh keeps a reference to the
 * last command in the "_" environment variable.  Since it does this after
 * doing aliases and pattern matching, "_" happens to hold the path to
 * whatever was executed.
 */

        char *myPath;  // holds ptr to the "_" variable contents
        char *myName;  // holds ptr to name of executable
        char *temp;    // holds temporary stuff (D'oh :-)

        temp = strrchr(argv[0],'/');  // set temp to last occur. of '/'
        if (temp != NULL) {           // if '/'s exist
                myName = temp + 1;    // set myName to remainder of string
        } else {                      // otherwise
                myName = argv[0];     // set myName to first arg.
        }

        myPath = getenv("_");        // get "_" variable from environment
        temp = strrchr(myPath,'/');  // set temp to last occur. of '/'
        *temp = '\0';                // strip off the executable name

        printf("\"%s\" is in directory: %s\n",myName,myPath);  // print

        return 0;
}

Q: My colleague finally sent me some critical files, but now he's off
   to Roswell for a millennium vigil, and I can't untar them!

   It looks like he gave absolute paths when he tar'ed the files, 
   but the system won't let me recreate the paths:

     c-yukon<36> tar tf progs.tar
     /tmp/vgt_tmp/progs/ellips.c
     /tmp/vgt_tmp/progs/genseq.c

     c-yukon<37> tar xf progs.tar
     cmd-3749 tar: mkdir '/tmp/vgt_tmp/progs' failed: Permission denied
     cmd-1004 tar: Cannot create '/tmp/vgt_tmp/progs/ellips.c'.
     cmd-3749 tar: mkdir '/tmp/vgt_tmp/progs' failed: Permission denied
     cmd-1004 tar: Cannot create '/tmp/vgt_tmp/progs/genseq.c'.

   How can I extract these files?

[ Answers, questions, and tips graciously accepted. ]

Thomas J. Baring	ARSC Web Specialist	ph: 907-450-8619
Donald Bahls	ARSC User Consultant	ph: 907-450-8674
Arctic Region Supercomputing Center
University of Alaska Fairbanks
PO Box 756020
Fairbanks AK 99775-6020

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