It looks like there was some discussion along these lines previously: http://www.jsoftware.com/pipermail/source/2016-May/000785.html
I also don't understand why gc3 is needed. It's also interesting that it changed some time between j v7 and the gpl source in j7 https://github.com/zeotrope/j7-src/blob/0fba52cac4035de6442c2716b614d7b232e91693/cp.c#L31 while(k<m&&i==nv[jv[k]]){xv[jv[k]]=z; ++k;} gc3(x,z,0L,old); https://github.com/jsoftware/jsource/blob/master/jsrc/cp.c#L97 while(k<m&&i==nv[k]){xv[k]=z; ++k; q=k<m?bv[k]:0;} if(!(i%10))gc3(x,z,0L,old); It looks like the (i%10) was added to make the gc3 run less frequently - every 10th iteration. If there was a loop of 11, then it wouldn't execute on the 11th iteration, which makes me wonder why it's even there in the first place -- maybe to free up temporary memory? That seems like an expensive operation to run every 10 iterations. I could see it making sense on memory constrained systems but seems less relevant now and actually is very costly from a CPU perspective On Tue, Jan 10, 2017 at 9:51 PM, Joe Bogner <joebog...@gmail.com> wrote: > I was investigating the slowness of this and identified a call to gc3 as > being the culprit > > > With the gc3: > > f1 =: 3 : '(>: each)^:(<y) (<0)' > > (6!:2) 'f1 100000' > 33.0624 > > Without it > > (6!:2) 'f1 100000' > 0.272726 > > > It still works: > f1 5 > +-+-+-+-+-+ > |0|1|2|3|4| > +-+-+-+-+-+ > > > Why is it doing this operation (garbage collection?) every 10 loops > > https://github.com/jsoftware/jsource/blob/e68277f408433fe34fd31f0161a31c > 96d9ccb44e/jsrc/cp.c#L97 > > > Can anyone elaborate on this? Is the 10 count too frequent? > > > Repeatedly running f1 100000 does not result in a memory leak as far as > I can tell. > cp.c > > static DF1(jtply1){PROLOG(0040);DECLFG;A b,hs,j,x,*xv,y,z;B*bv,q;I > i,k,m,n,*nv,old,p=0; > hs=sv->h; m=AN(hs); > RZ(x=ravel(hs)); RZ(y=from(j=grade1(x),x)); nv=AV(y); > GATV(x,BOX,m,1,0); xv=AAV(x); > while(p<m&&0>nv[p])p++; > if(p<m){ > RZ(z=ca(w)); > n=nv[m-1]; k=p; > while(k<m&&!nv[k]){xv[k]=z; ++k;} > RZ(b=eq(ainf,from(j,ravel(gs)))); bv=BAV(b); q=k<m?bv[k]:0; > old=jt->tnextpushx; > for(i=1;i<=n;++i){ > RZ(z=CALL1(f1,y=z,fs)); > if(q&&equ(y,z)){DO(m-k, xv[k]=z; ++k;); break;} > while(k<m&&i==nv[k]){xv[k]=z; ++k; q=k<m?bv[k]:0;} > if(!(i%10))gc3(x,z,0L,old); > }} > if(0<p){ > RZ(fs=inv(fs)); f1=VAV(fs)->f1; > RZ(z=ca(w)); > n=nv[0]; k=p-1; > RZ(b=eq(scf(-inf),from(j,ravel(gs)))); bv=BAV(b); q=bv[k]; > old=jt->tnextpushx; > for(i=-1;i>=n;--i){ > RZ(z=CALL1(f1,y=z,fs)); > if(q&&equ(y,z)){DO(1+k, xv[k]=z; --k;); break;} > while(0<=k&&i==nv[k]){xv[k]=z; --k; q=0<=k?bv[k]:0;} > # ----------------> if(!(i%10))gc3(x,z,0L,old); > }} > z=ope(reshape(shape(hs),from(grade1(j),x))); EPILOG(z); > } > > > > void jtgc3(J jt,A x,A y,A z,I old){ > if(x)ra(x); if(y)ra(y); if(z)ra(z); > tpop(old); > if(x)tpush(x); if(y)tpush(y); if(z)tpush(z); > } > > > > ---------- Forwarded message ---------- > From: Joe Bogner <joebog...@gmail.com> > Date: Tue, Jan 10, 2017 at 6:26 PM > Subject: Re: ^: slowness with boxes > To: programm...@jsoftware.com > > > For a little more color: previous discussion: http://www.jsoftwa > re.com/pipermail/programming/2014-March/035994.html > > I'm going to switch back to using i. for this > > > > On Tue, Jan 10, 2017 at 6:15 PM, Joe Bogner <joebog...@gmail.com> wrote: > >> Looks like it is due to the boxing. Please disregard >> >> http://code.jsoftware.com/wiki/Vocabulary/comma#dyadic mentions that >> append in place special code does not work for boxes >> >> f4 =: 3 : 0 >> >> a=:a: >> >> for_n. (i. y) do. a=:a,(<n) end. >> >> ) >> >> >> (6!:2) 'f4 100' >> >> 0.000336555 >> >> (6!:2) 'f4 1000' >> >> 0.0149772 >> >> (6!:2) 'f4 10000' >> >> 0.667025 >> >> (6!:2) 'f4 20000' >> >> 2.69115 >> >> (6!:2) 'f4 100000' >> >> 170.261 >> >> >> >> >> On Tue, Jan 10, 2017 at 5:26 PM, Joe Bogner <joebog...@gmail.com> wrote: >> >>> Why are these so different in execution speed? I'm surprised assembling >>> that linking boxes makes that much of a difference over an number. I need >>> it to be boxed because I'm going to something more complex with each >>> iteration. >>> >>> f1 =: 3 : '(>: each)^:(<y) (<0)' >>> >>> (6!:2) 'f1 100' >>> 6.01622e_5 >>> (6!:2) 'f1 1000' >>> 0.0012719 >>> (6!:2) 'f1 10000' >>> 0.145702 >>> (6!:2) 'f1 100000' >>> 33.0624 >>> >>> f2 =: 3 : '(>:)^:(<y) (0)' >>> >>> (6!:2) 'f2 100' >>> 4.24675e_5 >>> (6!:2) 'f2 1000' >>> 0.000189688 >>> (6!:2) 'f2 10000' >>> 0.00180487 >>> (6!:2) 'f2 100000' >>> 0.0256836 >>> >>> >>> I'm thinking of using ^: to execute something N times with an increasing >>> argument. >>> >>> I could use i. but wanted to try something different >>> >>> >>> JVERSION >>> >>> Engine: j805/j64/windows >>> >>> Release: commercial/2016-12-11T08:02:16 >>> >>> Library: 8.05.11 >>> >>> Qt IDE: 1.5.3s/5.6.2 >>> >>> Platform: Win 64 >>> >>> Installer: J805 install >>> >>> InstallPath: c:/program files/j64-805 >>> >>> Contact: www.jsoftware.com >>> >> >> > > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
