Scope storage class [Was: DMD 1.037 and 2.020 releases]
bearophile
bearophileHUGS at lycos.com
Wed Nov 26 04:34:54 PST 2008
To test the new scoping features of D 2.021 I have used a small stressing program, coming from this page, originally by Knuth:
http://www.rosettacode.org/wiki/Man_or_boy_test
More info:
http://en.wikipedia.org/wiki/Man_or_boy_test
My purpose is to see the D2 compiler being able to compute results up to N=25 on my PC (that has 2 GB RAM and a 32 bit operating system).
---------------------------
This is the code I have used for DMD 1.037:
import std.c.stdio: printf;
int a(int k, lazy int x1, lazy int x2, lazy int x3, lazy int x4, lazy int x5) {
int delegate() b;
b = {
k -= 1;
return a(k, b(), x1, x2, x3, x4);
};
return k <= 0 ? x4 + x5 : b();
}
void main() {
printf("%d\n", a(15, 1, -1, -1, 1, 0)); // N is 15
}
---------------------------
This is the code I have used for DMD 2.021. I was not sure how to use the scope, so if you have improvements please tell me:
import std.c.stdio: printf;
int a(scope int k, lazy int x1, lazy int x2, lazy int x3, lazy int x4, lazy int x5) {
scope int delegate() b;
b = {
k -= 1;
return a(k, b(), x1, x2, x3, x4);
};
return k <= 0 ? x4 + x5 : b();
}
void main() {
printf("%d\n", a(15, 1, -1, -1, 1, 0)); // N is 15
}
---------------------------
The results for higher values of N are:
k 21 22 23 24 25
A -389695 -865609 -1922362 -4268854 -9479595
In both cases I have compiled the code with:
dmd -O -release -inline -L/STACK:1700000000 man_or_boy.d
The results:
DMD V.1.037 (exe: 168_476: bytes):
N=24: 788 MB RAM, 3 seconds
N=25: 1.57 GB RAM, 6.42 seconds
DMD V.2.021 (exe: 99_356 bytes):
The code was too much slow in D2, so I have stopped it. Do you know if the D2 code can be improved to have performance similar to D1 ones?
Bye,
bearophile
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