Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!uvaarpa!mcnc!ncsuvx!csl!harish
From: harish@csl.ncsu.edu (Harish Hiriyannaiah)
Newsgroups: comp.lang.c
Subject: Re: Style for handling matrices in C
Message-ID: <4204@ncsuvx.ncsu.edu>
Date: 17 Oct 89 02:01:27 GMT
References: <7229@cognos.UUCP> <278@dsi.COM>
Sender: news@ncsuvx.ncsu.edu
Reply-To: harish@csl.UUCP (Harish Hiriyannaiah)
Organization: North Carolina State University
Lines: 29

In article <278@dsi.COM> dave@dsi.UUCP (Dave Rifkind) writes:
-Here's one that doesn't require any special action to free up the
-matrix:
-
-     double **mat_alloc(row, col)
-     {
-	  int i;
-	  double *dp, **dpp;
-
-	  dpp = malloc(row * sizeof(double *) + row * col * sizeof(double));
-	  if (dpp != NULL) {
-	       dp = dpp + row;
-	       for (i = 0; i < row; i++)
-		    dpp[i] = dp + i * col;
-	  }
-	  return dpp;
-     }



	Here you are assuming that the pointers are word aligned, which
	can be pretty dangerous.....

	Consider, for example short pointers to floats. If we have 7 rows
	(or any odd number), then the allocated space for the first float
	will fall on a 16-bit boundary..... 

harish pu. hi.				harish@ecelet.ncsu.edu
					harish@ecebucolix.ncsu.edu