A quick post. I implemented matrix multiplication in Dart. It takes Dart 12 seconds to multiply two 500×500 matrices. In contrast, LuaJIT does the same job in less than 0.2 seconds. Perl takes 26 seconds. This means that Dart fails to JIT the critical loop even though I am trying to use explicit typing. Dart is not quite there yet to match the performance of V8 and LuaJIT. The source code is appended. It looks almost the same as C++.
mat_transpose(a)
{
int m = a.length, n = a[0].length; // m rows and n cols
var b = new List(n);
for (int j = 0; j < n; ++j) b[j] = new List<double>(m);
for (int i = 0; i < m; ++i)
for (int j = 0; j < n; ++j)
b[j][i] = a[i][j];
return b;
}
mat_mul(a, b)
{
int m = a.length, n = a[0].length, s = b.length, t = b[0].length;
if (n != s) return null;
var x = new List(m), c = mat_transpose(b);
for (int i = 0; i < m; ++i) {
x[i] = new List<double>(t);
for (int j = 0; j < t; ++j) {
double sum = 0;
var ai = a[i], cj = c[j];
for (int k = 0; k < n; ++k) sum += ai[k] * cj[k];
x[i][j] = sum;
}
}
return x;
}
mat_gen(int n)
{
var a = new List(n);
double t = 1.0 / n / n;
for (int i = 0; i < n; ++i) {
a[i] = new List<double>(n);
for (int j = 0; j < n; ++j)
a[i][j] = t * (i - j) * (i + j);
}
return a;
}
main()
{
int n = 500;
var a = mat_gen(n);
var b = mat_gen(n);
var c = mat_mul(a, b);
print(c[n~/2][n~/2]);
}
Attractive Chaos 