diff Problems/private/rowlincomb.c @ 10:207a6ae9a76f version1.0

(none)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Problems/private/rowlincomb.c	Mon Mar 22 15:06:25 2010 +0000
@@ -0,0 +1,148 @@
+/**************************************************************************
+ *
+ * File name: rowlincomb.c
+ *
+ * Ron Rubinstein
+ * Computer Science Department
+ * Technion, Haifa 32000 Israel
+ * ronrubin@cs
+ *
+ * Last Updated: 21.5.2009
+ *
+ *************************************************************************/
+
+#include "mex.h"
+
+
+/* Input Arguments */
+
+#define	X_IN	   prhs[0]
+#define A_IN     prhs[1]
+#define ROWS_IN  prhs[2]
+#define COLS_IN  prhs[3]
+
+
+/* Output Arguments */
+
+#define	Y_OUT	plhs[0]
+
+
+void mexFunction(int nlhs, mxArray *plhs[],
+int nrhs, const mxArray*prhs[])
+
+{
+  double *A, *x, *y, *rows, *cols;
+  mwSize m,n,m1,n1,m2,n2,rownum,colnum;
+  mwIndex *row_ids,*col_ids,i,j;
+  int colnumspecified=0;
+  
+  
+  /* Check for proper number of arguments */
+  
+  if (nrhs!=3 && nrhs!=4) {
+    mexErrMsgTxt("Invalid number of input arguments.");
+  } else if (nlhs > 1) {
+    mexErrMsgTxt("Too many output arguments.");
+  }
+  
+  
+  /* Check the input dimensions */
+  
+  m = mxGetM(A_IN);
+  n = mxGetN(A_IN);
+  if (!mxIsDouble(A_IN) || mxIsComplex(A_IN) || mxGetNumberOfDimensions(A_IN)>2) {
+    mexErrMsgTxt("ROWLINCOMB requires that A be a double matrix.");
+  }
+  
+  m1 = mxGetM(ROWS_IN);
+  n1 = mxGetN(ROWS_IN);
+  if (!mxIsDouble(ROWS_IN) || mxIsComplex(ROWS_IN) || (m1!=1 && n1!=1)) {
+    mexErrMsgTxt("ROWLINCOMB requires that ROWS be an index vector of type double.");
+  }
+  rownum = (m1 > n1) ? m1 : n1;   /* the number of rows in the linear combination */
+  
+  m2 = mxGetM(X_IN);
+  n2 = mxGetN(X_IN);
+  if (!mxIsDouble(X_IN) || mxIsComplex(X_IN) || ((m2!=1) && (n2!=1))) {
+    mexErrMsgTxt("ROWLINCOMB requires that X be a double vector.");
+  }
+  
+  if (m2 != rownum && n2 != rownum) {
+    mexErrMsgTxt("The length of X does not match the number of rows in ROWS.");
+  }
+  
+  if (nrhs==4) {
+    m1 = mxGetM(COLS_IN);
+    n1 = mxGetN(COLS_IN);
+    if (!mxIsDouble(COLS_IN) || mxIsComplex(COLS_IN) || (m1!=1 && n1!=1)) {
+      mexErrMsgTxt("ROWLINCOMB requires that COLS be an index vector of type double.");
+    }
+    colnum = (m1 > n1) ? m1 : n1;   /* the number of columns */
+    colnumspecified = 1;
+    cols = mxGetPr(COLS_IN);
+    
+    Y_OUT = mxCreateDoubleMatrix(1, colnum, mxREAL);
+  }
+  else {
+    cols = 0;
+    Y_OUT = mxCreateDoubleMatrix(1, n, mxREAL);
+  }
+  
+  
+  /* Assign pointers to the various parameters */
+  A = mxGetPr(A_IN);
+  rows = mxGetPr(ROWS_IN);
+  x = mxGetPr(X_IN);
+  y = mxGetPr(Y_OUT);
+  
+  
+  /* check row indices */
+  
+  row_ids = (mwIndex*)mxMalloc(rownum*sizeof(mwIndex));
+  
+  for (i=0; i<rownum; ++i) {
+    row_ids[i] = (mwIndex)(rows[i]+0.1)-1;
+    if (row_ids[i]<0 || row_ids[i]>=m) {
+      mexErrMsgTxt("Row index in ROWS is out of range.");
+    }
+  }
+  
+  
+  
+  if (colnumspecified) {
+    
+    /* check column indices */
+    col_ids = (mwIndex*)mxMalloc(colnum*sizeof(mwIndex));
+    
+    for (i=0; i<colnum; ++i) {
+      col_ids[i] = (mwIndex)(cols[i]+0.1)-1;
+      if (col_ids[i]<0 || col_ids[i]>=n) {
+        mexErrMsgTxt("Column index in COLS is out of range.");
+      }
+    }
+    
+    /* Do the actual computation */
+    for (j=0; j<colnum; ++j) {
+      for (i=0; i<rownum; ++i) {
+        y[j] += A[m*col_ids[j]+row_ids[i]]*x[i];
+      }
+    }
+    
+    mxFree(col_ids);
+  }
+  
+  else {
+    
+    /* Do the actual computation */
+    for (j=0; j<n; ++j) {
+      for (i=0; i<rownum; ++i) {
+        y[j] += A[m*j+row_ids[i]]*x[i];
+      }
+    }
+  }
+  
+  
+  mxFree(row_ids);
+  
+  return;
+}