Opened 12 years ago
Last modified 8 years ago
#8158 new enhancement
efficiency problem with polynomials (SymbolicRing vs PolynomialRing)
Reported by: | zimmerma | Owned by: | tbd |
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Priority: | major | Milestone: | sage-wishlist |
Component: | performance | Keywords: | |
Cc: | Merged in: | ||
Authors: | Reviewers: | ||
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description
Consider the following example:
sage: var('a,b,c') (a, b, c) sage: time d=expand((a+b+c+1)^100) CPU times: user 2.45 s, sys: 0.07 s, total: 2.52 s Wall time: 2.53 s
I thought it would be more efficient to use PolynomialRing?(), but it is not:
sage: P.<a,b,c> = PolynomialRing(QQ) sage: time d=(a+b+c+1)^100 CPU times: user 10.28 s, sys: 0.07 s, total: 10.35 s Wall time: 12.59 s
However if one wants to factor d, then PolynomialRing? is faster (SymbolicRing? seems to loop forever):
sage: time e = d.factor() CPU times: user 28.87 s, sys: 0.36 s, total: 29.23 s Wall time: 34.20 s
Change History (7)
comment:1 Changed 9 years ago by
- Milestone changed from sage-5.11 to sage-5.12
comment:2 Changed 9 years ago by
comment:3 Changed 8 years ago by
- Milestone changed from sage-6.1 to sage-6.2
comment:4 Changed 8 years ago by
I doubt there is much to do here except reduce the overhead of the singular interface (especially regarding memory management) or singular itself. On my system, ginac (1.6.2) is already faster than singular (3.1.6):
> time(expand((a+b+c+1)^100)); 1.184s
> timer=1; > ring r=0,(a,b,c),lp; > poly p=(a+b+c+1)^100; //used time: 1.95 sec
Both interfaces have comparable overhead (sage 6.2.beta4):
sage: %time _=expand((a+b+c+1)^100) CPU times: user 3.13 s, sys: 16 ms, total: 3.14 s Wall time: 3.14 s
sage: P.<a,b,c> = PolynomialRing(QQ,order='lex') sage: %time _=(a+b+c+1)^100 CPU times: user 5.59 s, sys: 8 ms, total: 5.6 s Wall time: 5.59 s
but not for the same reason—the advantage of standalone singular over libsingular called from sage seems to be due in large part to its faster memory allocator, and we can make the singular version significantly faster by forcing sage to use tcmalloc instead of the system malloc():
$ LD_PRELOAD="/usr/lib/libtcmalloc.so.4" sage ... sage: var('a,b,c') (a, b, c) sage: %time _=expand((a+b+c+1)^100) CPU times: user 2.89 s, sys: 36 ms, total: 2.92 s Wall time: 2.92 s sage: P.<a,b,c> = PolynomialRing(QQ,order='lex') sage: %time _=(a+b+c+1)^100 CPU times: user 3.4 s, sys: 12 ms, total: 3.41 s Wall time: 3.41 s
comment:5 follow-up: ↓ 7 Changed 8 years ago by
the speedup obtained with tcmalloc is impressive, could this be useful in other parts of Sage?
Paul
comment:6 Changed 8 years ago by
- Component changed from commutative algebra to performance
- Milestone changed from sage-6.2 to sage-wishlist
- Owner changed from malb to tbd
- Type changed from defect to enhancement
PolynomialRing? is still slower with Sage 5.11, even with integer coefficients:
Paul