diff Problems/private/sprow.c @ 15:51b76c31c93d

(none)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Problems/private/sprow.c	Thu Mar 25 14:05:27 2010 +0000
@@ -0,0 +1,94 @@
+/**************************************************************************
+ *
+ * File name: sprow.c
+ *
+ * Ron Rubinstein
+ * Computer Science Department
+ * Technion, Haifa 32000 Israel
+ * ronrubin@cs
+ *
+ * Last Updated: 24.8.2009
+ *
+ *************************************************************************/
+
+
+#include "mex.h"
+#include "mexutils.h"
+
+
+/* Input Arguments */
+
+#define	A_IN	prhs[0]
+#define J_IN  prhs[1]
+
+
+/* Output Arguments */
+
+#define	X_OUT	  plhs[0]
+#define	ID_OUT	plhs[1]
+
+
+void mexFunction(int nlhs, mxArray *plhs[], 
+		             int nrhs, const mxArray*prhs[])
+     
+{ 
+  double *pr, *x, *id, rowid;
+  mwIndex *ir, *jc;
+  mwSize m, n;
+  mwIndex i, j, k, l, rowlen;
+  
+  if (nrhs != 2) {
+    mexErrMsgTxt("GETSPROW requires two input arguments.");
+  } else if (nlhs > 2) {
+    mexErrMsgTxt("Too many output arguments.");
+  }
+  
+  checkmatrix(A_IN, "GETSPROW", "A");
+  checksparse(A_IN, "GETSPROW", "A");
+  checkscalar(J_IN, "GETSPROW", "J");
+  
+  m = mxGetM(A_IN);
+  n = mxGetN(A_IN);
+  
+  rowid = mxGetScalar(J_IN);
+  if (rowid < 0) {
+    mexErrMsgTxt("Invalid row index.");
+  }
+  j = (mwIndex)(rowid + 1e-2);
+  if (j<1 || j>m) {
+    mexErrMsgTxt("Row index is out of range.");
+  }
+  j--;
+  
+  pr = mxGetPr(A_IN);
+  ir = mxGetIr(A_IN);
+  jc = mxGetJc(A_IN);
+  
+  /* Determine length of row */
+  rowlen = 0;
+  for (i=0; i<jc[n]; ++i) {
+    rowlen += (ir[i]==j);
+  }
+  
+  /* Allocate output parameters */
+  X_OUT = mxCreateDoubleMatrix(1, rowlen, mxREAL);
+  ID_OUT = mxCreateDoubleMatrix(1, rowlen, mxREAL);
+  
+  x = mxGetPr(X_OUT);
+  id = mxGetPr(ID_OUT);
+  
+  /* Compute j-th row */
+  k=0;
+  for (l=1; l<=n; ++l) {
+    i = jc[l-1];
+    while (i<jc[l] && ir[i]<j) {
+      i++;
+    }
+    if (i<jc[l] && ir[i]==j) {
+      x[k] = pr[i];
+      id[k] = l;
+      k++;
+    }
+  }
+  
+}