On Thursday, 28 March 2024 at 01:09:34 UTC, Salih Dincer wrote:
Good thing you're digressing; I am 45 years old and I still
cannot say that I am finished as a student! For me this is
version 4 and it looks like we don't need a 3rd variable other
than the function parameter and return value:
So we go with another digression. I discovered parallel, also
avoided the extra variable, as suggested by Salih:
```d
import std.range;
import std.parallelism;
import core.stdc.stdio: printf;
import std.datetime.stopwatch;
enum ITERS = 1_000_000_000;
enum STEPS = 31; // 5 is fine, even numbers (e.g. 10) may give
bad precision (for math reason ???)
pure double leibniz(int i) { // sum up the small values first
double r = (i == ITERS) ? 0.5 * ((i%2) ? -1.0 : 1.0) / (i * 2.0
+ 1.0) : 0.0;
for (--i; i >= 0; i-= STEPS)
r += ((i%2) ? -1.0 : 1.0) / (i * 2.0 + 1.0);
return r * 4.0;
}
void main() {
auto start = iota(ITERS, ITERS-STEPS, -1).array;
auto sw = StopWatch(AutoStart.yes);
double result = 0.0;
foreach(s; start.parallel)
result += leibniz(s);
double total_time = sw.peek.total!"nsecs";
printf("%.16f\n", result);
printf("Execution time: %f\n", total_time / 1e9);
}
```
gives:
```
3.1415926535897931
Execution time: 0.211667
```
My laptop has 6 cores and obviously 5 are used in parallel by
this.
The original question related to a comparison between C, D and
Python.
Turning back to this: Are there similarly simple libraries for C,
that allow for
parallel computation?
