Scope storage class [Was: DMD 1.037 and 2.020 releases]

[Jesse Phillips]

On Wed, 26 Nov 2008 12:18:27 -0800, Robert Fraser wrote:

> bearophile wrote:
>> 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
> 
> Try marking all the "lazy" parameters as "scope" ("lazy" creates
> delegates).