78 lines
978 B
C++
78 lines
978 B
C++
// Compute the trace of a matrix (sum of diagonal elements)
|
|
|
|
#include "stdafx.h"
|
|
#include "defs.h"
|
|
static void ytrace(void);
|
|
|
|
void
|
|
eval_trace(void)
|
|
{
|
|
push(cadr(p1));
|
|
eval();
|
|
trace();
|
|
}
|
|
|
|
void
|
|
trace(void)
|
|
{
|
|
save();
|
|
ytrace();
|
|
restore();
|
|
}
|
|
|
|
static void
|
|
ytrace(void)
|
|
{
|
|
int i, n;
|
|
|
|
p1 = pop();
|
|
|
|
// trace of scalar is ok even though contract(scalar) is not
|
|
|
|
if (isnum(p1)) {
|
|
push(p1);
|
|
return;
|
|
}
|
|
|
|
if (!istensor(p1)) {
|
|
push_symbol(TRACE);
|
|
push(p1);
|
|
list(2);
|
|
return;
|
|
}
|
|
|
|
if (p1->u.tensor->ndim != 2 || p1->u.tensor->dim[0] != p1->u.tensor->dim[1])
|
|
stop("trace(m): m is not a square matrix");
|
|
|
|
n = p1->u.tensor->dim[0];
|
|
|
|
for (i = 0; i < n; i++)
|
|
push(p1->u.tensor->elem[n * i + i]);
|
|
|
|
addk(n);
|
|
}
|
|
|
|
static char *s[] = {
|
|
|
|
"trace(A)",
|
|
"trace(A)",
|
|
|
|
"trace(0)",
|
|
"0",
|
|
|
|
"trace(1)",
|
|
"1",
|
|
|
|
"trace(((a,b),(c,d)))",
|
|
"a+d",
|
|
|
|
"trace((a,b))",
|
|
"Stop: trace(m): m is not a square matrix",
|
|
};
|
|
|
|
void
|
|
test_trace(void)
|
|
{
|
|
test(__FILE__, s, sizeof s / sizeof (char *));
|
|
}
|