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svn path=/trunk/externals/iem/iemmatrix/; revision=2638

1 files changed, 118 insertions, 0 deletions

diff --git a/src/mtx_inverse.c b/src/mtx_inverse.c
new file mode 100644
index 0000000..400f734
--- /dev/null
+++ b/src/mtx_inverse.c
@@ -0,0 +1,118 @@
+/*
+ *  iemmatrix
+ *
+ *  objects for manipulating simple matrices
+ *  mostly refering to matlab/octave matrix functions
+ *
+ * (c) IOhannes m zmölnig, forum::für::umläute
+ * 
+ * IEM, Graz
+ *
+ * this code is published under the LGPL
+ *
+ */
+#include "iemmatrix.h"
+
+/* mtx_inverse */
+static t_class *mtx_inverse_class;
+
+static void mtx_inverse_matrix(t_matrix *x, t_symbol *s, int argc, t_atom *argv)
+{
+  /* maybe we should do this in double or long double ? */
+  int row=atom_getfloat(argv);
+  int col=atom_getfloat(argv+1);
+  int i, k, row2=row*row;
+
+  t_matrixfloat *original, *inverted;
+  t_matrixfloat *a1, *a2, *b1, *b2;  // dummy pointers
+
+  int ok = 0;
+
+  if(row*col+2>argc){
+    post("mtx_print : sparse matrices not yet supported : use \"mtx_check\"");
+    return;
+  }
+  if (row!=col){
+    post("mtx_inverse: only square matrices can be inverted");
+    return;
+  }
+
+  // reserve memory for outputting afterwards
+  adjustsize(x, row, row);
+  // 1. get the 2 matrices : orig; invert (create as eye, but will be orig^(-1))
+  inverted = (t_matrixfloat *)getbytes(sizeof(t_matrixfloat)*row2);
+  // 1a extract values of A to float-buf
+  original=matrix2float(argv);
+  // 1b make an eye-shaped float-buf for B
+  i=row2;
+  b1=inverted;
+  while(i--)*b1++=0;
+  i=row;
+  b1=inverted;
+  while(i--)b1[i*(row+1)]=1;
+
+  // 2. do the Gauss-Jordan
+  for (k=0;k<row;k++) {
+    // 2. adjust current row
+    t_matrixfloat diagel = original[k*(col+1)];
+    t_matrixfloat i_diagel = diagel?1./diagel:0;
+    if (!diagel)ok++;
+
+
+    /* normalize current row (set the diagonal-element to 1 */
+    a2=original+k*col;
+    b2=inverted+k*col;
+    i=row;
+    while(i--){
+      *a2++*=i_diagel;
+      *b2++*=i_diagel;
+    }
+    /* eliminate the k-th element in each row by adding the weighted normalized row */
+
+    a2=original+k*row;
+    b2=inverted+k*row;
+    for(i=0;i<row;i++)
+      if (i-k) {
+	t_matrixfloat f=-*(original+i*row+k);
+	int j = row;
+	a1=original+i*row;
+	b1=inverted+i*row;
+	while (j--) {
+	  *(a1+j)+=f**(a2+j);
+	  *(b1+j)+=f**(b2+j);
+	}
+      }
+  }
+  // 3. output the matrix
+  // 3a convert the floatbuf to an atombuf;
+  float2matrix(x->atombuffer, inverted);
+  // 3b destroy the buffers
+  freebytes(original, sizeof(t_matrixfloat)*row2);
+
+  if (ok)post("mtx_inverse: couldn't really invert the matrix !!! %d error%c", ok, (ok-1)?'s':0);
+
+  // 3c output the atombuf;
+  matrix_bang(x);
+}
+
+static void *mtx_inverse_new(t_symbol *s, int argc, t_atom *argv)
+{
+  t_matrix *x = (t_matrix *)pd_new(mtx_inverse_class);
+  outlet_new(&x->x_obj, 0);
+  x->col=x->row=0;
+  x->atombuffer=0;
+
+  return (x);
+}
+void mtx_inverse_setup(void)
+{
+  mtx_inverse_class = class_new(gensym("mtx_inverse"), (t_newmethod)mtx_inverse_new, 
+				(t_method)matrix_free, sizeof(t_matrix), 0, A_GIMME, 0);
+  class_addbang  (mtx_inverse_class, matrix_bang);
+  class_addmethod(mtx_inverse_class, (t_method)mtx_inverse_matrix, gensym("matrix"), A_GIMME, 0);
+  class_sethelpsymbol(mtx_inverse_class, gensym("iemmatrix/mtx_inverse"));
+}
+
+void iemtx_inverse_setup(void){
+  mtx_inverse_setup();
+}