User talk:Retroburrowers

My response isposted here: U r critiquing alphaversions abandoned infavor of a beta which does find the answer, but may also find false positives due to lack of precision. Please test the beta on fuse, and post your versions after my beta, which I can't run not having a Next w/1.5 MB ram -- A little info why your programs did not give results.

<lang zxbasic> 5 FOR r=34 TO 5 STEP -1 10 FOR m=r TO 249 STEP 30 20 FOR w=4 TO (m-1):FOR x=3 TO (w-1):FOR y=2 TO (x-1):FOR z=1 TO (y-1) 30 LET sum=INT(w^4/m*w + x^4/m*x + y^4/m*y + z^4/m*z + 0.5) 40 LET s1=m^4 45 IF sum>s1 THEN GO TO 65 50 IF s1=sum THEN PRINT w;"^5+";x;"^5+";y;"^5+";z;"^5=";m;"^5": STOP 60 NEXT z: NEXT y: NEXT x: NEXT w 65 NEXT m: NEXT r</lang>

<lang zxbasic> 2 DIM p(249) : DIM q(249)

4 FOR i=1 TO 249 
5  LET p(i)=i*i : LET q(i)=p(i)*i
6 NEXT i
8 FOR r=34 TO 5 STEP -1

10 FOR m=r TO 249 STEP 30 20 FOR w=4 TO (m-1): FOR x=3 TO (w-1): FOR y=2 TO (x-1): FOR z=1 TO (y-1) 30 LET sum=INT(q(w)/q(m)*p(w) + q(x)/q(m)*p(x) + q(y)/q(m)*p(y) + q(z)/q(m)*p(z) +0.5) 40 LET s1=p(m) 45 IF sum>s1 THEN GO TO 65 50 IF s1=sum THEN PRINT w;"^5+";x;"^5+";y;"^5+";z;"^5=";m;"^5": STOP 60 NEXT z: NEXT y: NEXT x: NEXT w 65 NEXT m: NEXT r<lang>

<lang zxbasic> 2 DIM p(249) : DIM q(249)

4 FOR i=1 TO 249 
5  LET q(i)=LN i
6 NEXT i
8 FOR r=34 TO 5 STEP -1

10 FOR m=r TO 249 STEP 30 20 FOR w=4 TO (m-1): FOR x=3 TO (w-1): FOR y=2 TO (x-1): FOR z=1 TO (y-1) 30 LET sum=EXP(q(w)-q(m)) + EXP(q(x)-q(m)) + EXP(q(y)-q(m)) + EXP(q(z)-q(m)) 35 IF sum>1 THEN GO TO 65 50 IF sum=1 THEN PRINT w;"^5+";x;"^5+";y;"^5+";z;"^5=";m;"^5": STOP 60 NEXT z: NEXT y: NEXT x: NEXT w 65 NEXT m: NEXT r</lang>

All these versions have 1 fatal flaw. When sum it greater then a certain value they jump to <lang zxbasic>NEXT m</lang> instead they should jump to <lang zxbasic>NEXT y</lang>

Let's say that m = 10 and

 w     x     y     z
8^5 + 7^5 + 6^5 + 5^5 = 32768 + 16807 + 7776 + 3125 = 60476 
9^5 + 3^5 + 2^5 + 1^5 = 59049 +   243 +   32 +    1 = 59325

To demonstrate this let's take version and alter it a little bit in order to give a fast result.
We set m to 144, w to 133 ,x to 110, and y = 70 to speed things up.
<lang zxbasic> 2 DIM p(249) : DIM q(249)
4 FOR i=1 TO 249 
5 LET p(i)=i*i : LET q(i)=p(i)*i
6 NEXT i

10 FOR m=144 TO 144 STEP 30 : let s1=p(m) 20 FOR w=133 TO (m-1): FOR x=110 TO (w-1): FOR y=70 TO (x-1): FOR z=1 TO (y-1) 30 LET sum=INT(q(w)/q(m)*p(w) + q(x)/q(m)*p(x) + q(y)/q(m)*p(y) + q(z)/q(m)*p(z) +0.5) 45 IF sum>s1 THEN GO TO 65 50 IF s1=sum THEN PRINT w;"^5+";x;"^5+";y;"^5+";z;"^5=";m;"^5": STOP 60 NEXT z 61 NEXT y: NEXT x: NEXT w 65 NEXT m: </lang>

Run it and simple stops with out a result, since m does not increase we can check the value of y and z, y = 74, z = 73. In line 45 change <lang zxbasic>GO TO 65</lang> to <lang zxbasic>GO TO 61</lang>. Rerun it and after a while it will produce the correct answer 133^5+110^5+84^5+27^5=144^5.

Please remember that the ZX Spectrum is 38 years old and it was not designed for this kind of tasks, it was a cheap and simple computer. --Frisian (talk) 15:15, 30 April 2020 (UTC)

<lang zxbasic> 5 DIM p(249): DIM q(249): DIM r(249,249) 10 FOR i=1 TO 249: LET q(i)=5*LN i: LET p(i)=q(i)/2: NEXT i 15 FOR j=1 TO 249: FOR k=1 TO 249: LET r(j,k)=EXP(q(j)-p(k)): NEXT k: NEXT j 20 FOR w=7 TO 245 STEP 7: FOR x=5 TO 245 STEP 5: FOR y=3 TO 246 STEP 3: FOR z=2 TO 248 STEP 2 25 FOR m=8 TO 249 30 LET sum=r(w,m)+ r(x,m) + r(y,m) + r(z,m) 35 LET lnsum=LN sum 50 IF lnsum=p(m) THEN PRINT w;"^5+";x;"^5+";y;"^5+";z;"^5=";m;"^5": STOP 55 IF lnsum>p(m) THEN NEXT m 60 NEXT z: NEXT y: NEXT x: NEXT w </lang>

This code will not run on ZX Spectrum nor on Fuse. In line 5 the last dim statement uses to much memory 249*249*5 = 310005 Bytes, this is even more then the total amount of memory for a ZX Spectrum 128. Therefore it´s not a ZX Spectrum program. Also it has the same flaw as the other version it will not find the solution.

Please check [ZX Spectrum page] --Frisian (talk) 17:44, 30 April 2020 (UTC)