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Questions tagged [lower-bounds]

questions about lowerbounds on functions, usually the complexity of an algorithm or a problem

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Monotone complexity of s-t connectivity

In the problem CONN, we obtain a directed $n$-vertex graph (encoded as a boolean string of $n^2$ bits, one for each potential edge), and want to decide whether there is a path between all $n^2$ pairs $...
Stasys's user avatar
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32 votes
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Combinatorics of Bellman-Ford or how to make cyclic graphs acyclic?

Roughly speaking, my question is: How costly is to make a cyclic graph acyclic while preserving all simple $s$-$t$ paths? Let $K_n$ be a complete undirected graph on vertices $\{0,1,\ldots,n+1\}$. (...
Stasys's user avatar
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19 votes
0 answers
1k views

Lower bounds on single-source shortest paths in directed graphs

Are there any non-trivial lower bounds on the complexity of single-source shortest paths (SSSP) in a directed graph, where all edges have non-negative edge weights? Can we rule out the possibility of ...
D.W.'s user avatar
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17 votes
0 answers
493 views

Can short-distance connectivity be harder than connectivity?

Has anybody seen the following (or similar) question being considered: Can it be easier to determine the presence/absence of $s$-$t$ paths than to determine the presence/absence of short $s$-$t$ ...
Stasys's user avatar
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15 votes
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419 views

Set Intersection lower bounds

Consider $S_1, ...,S_n \subseteq [U]$ where size of $U$ is polylogarithmic in $n$. We allow infinite time to pre-process these sets and then ask queries of the form $S_i \cap S_j$ is empty or not. We ...
karmanaut's user avatar
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15 votes
1 answer
444 views

Characterization of read-once formulae over the full binary basis

Background A read-once formula over a set of gates (also called a basis) is a formula in which each input variable appears once. Read-once formulas are commonly studied over the De Morgan basis (...
Robin Kothari's user avatar
12 votes
0 answers
287 views

Hardness of optimal sorting

For comparison-based sorting algorithms, asymptotically optimal algorithms in worst-case $\Theta(n\log n)$ comparisons are well known. From a purely theoretical perspective, however, exactly optimal ...
Joseph Stack's user avatar
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10 votes
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317 views

Monotone circuit complexity of matroids?

Call a monotone boolean function $f$ a matroid function if its minterms are bases of some matroid. I am interested in monotone circuit complexity of such functions, even when we "tie hands" of these ...
Stasys's user avatar
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10 votes
0 answers
174 views

Hardness in P: methods to show optimality of $O(m^2n)$-like time?

In recent years, there has been exciting work in proving lower bounds for polynomial-time problems conditional on conjectures like SETH or "All-Pairs-Shortest-Paths (APSP) cannot be solved in $O(|V|^{...
Dominik Peters's user avatar
10 votes
0 answers
288 views

Lower bound method for ordered binary decision diagrams

This is an idea/question inspired by the question and answer of Boolean functions with exponential size OBDD representation in all orders except one order?: If you want to prove some exponential ...
Marc Bury's user avatar
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9 votes
0 answers
206 views

Fourth(?) moment method for minimum value

I would like to lower bound the quantity $\Pr[X\ge t, Y\ge t]=\Pr[\min(X,Y)\ge t]$ using the small moments of $X$, $Y$ and $XY$. In particular I am interested in the case where $E[X]=E[Y]=0$, but $E[X ...
Thomas Ahle's user avatar
9 votes
0 answers
547 views

How to prove "obvious" facts?

The title is somewhat "arrogant": say, most of us treat $P\neq NP$ as an "obvious" fact, albeit no proof is in sight. But my question is at a much, much lower level, is about a fact which "should be" ...
Stasys's user avatar
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9 votes
0 answers
217 views

References for de-amortization

I've been interested in looking into the area of de-amortization recently (i.e. finding data structures with matching worst-case and amortized running time bounds, or exhibiting lower bounds against ...
rahulmehta95's user avatar
8 votes
0 answers
151 views

What is the least compressible probability distribution? (under entropy constraint, for an expected squared error metric)

Consider a distribution $\mathcal D$ over the reals, a real parameter $H\in\mathbb R^+$, and an integer parameter $k\in\mathbb N$. The Entropy-Constrained Quantization problem asks what is the best ...
R B's user avatar
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8 votes
0 answers
118 views

Reference for a circuit lower bound for slightly superexponential time

It is known that $EXP$ doesn't have circuits of size $n^k$. On the other hand proving $10 n$ lower bound on circuit size for $E$, $NE$ or even $E^{NP}$ is a known open problem. My question is ...
ivmihajlin's user avatar
8 votes
0 answers
310 views

Grigoriev-Karpinski for the permanent

Grigoriev and Karpinski (ps.Z) showed that any depth-3 circuit over a fixed finite field computing $\mathrm{Det}_n$ requires $2^{\Omega(n)}$ size. I had the misconception(?) until recently that the ...
Ramprasad's user avatar
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8 votes
0 answers
261 views

Existence of "colouring matrices" — a generalisation

This is a generalisation of the following post: Existence of "colouring matrices". As the base case turned out to be fairly straightforward (in essence, precisely equal to the existence of Sperner ...
Jukka Suomela's user avatar
8 votes
0 answers
259 views

For median is it optimal to compare in pairs first?

Median can be done in linear time and is now down to (I think) $2.97n$. The lower bounds is (I think) $(2+\epsilon)n$ where $\epsilon$ is very small. The following theorem, if true, may help improve ...
Bill GASARCH's user avatar
7 votes
0 answers
321 views

Why is it so difficult to study Sum of Squares (SoS) algorithms with degree $d>4$?

In many publications on the computational complexity of Sum of Squares (SoS) algorithms, it is typical to study the degree-$4$ relaxation; e.g. Rounding Sum-of-Squares Relaxations Sum-of-Squares ...
Steve's user avatar
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7 votes
0 answers
158 views

Size complexity of probabilistic two-way automata for a Boolean function

I'm interested in computing Boolean functions $f:\{0,1\}^n\rightarrow\{0,1\}$ with two-way finite automata and I will measure the complexity of a Boolean function by the number of states for the ...
kbkb's user avatar
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7 votes
0 answers
245 views

Data structures lower bounds on Turing machines

Have there been any results on lower bounds for implementing data structures on Turing machines, e.g. stacks, queues, etc ? I guess that people are mostly interested in models with random access, but ...
yagrad's user avatar
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6 votes
0 answers
122 views

Proof complexity of Sudoku

Let $P$ be a $N$x$N$ Sudoku puzzle (assume $N=n^2$ for some $n\in \mathbb{N}$, e.g. standard $9$x$9$ puzzle is $n=3$). We can represent it in propositional logic as follows: Variables $p_{i,j,k}$: ...
Kaveh's user avatar
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6 votes
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165 views

Are exponential lower bounds known against $MOD_6 \circ MOD_3$ circuits computing $OR$?

Background What is currently known for depth-2 $CC^0$ circuits with restricted gate types: In [1] it is shown that $(MOD_p)^k \circ MOD_m$ circuits (that is, $k$ layers of $MOD_p$ gates at the output)...
Jake's user avatar
  • 1,214
6 votes
0 answers
153 views

$\mathbf{AC}^0$ lower bounds for $\mathsf{Gap}\text{-}\mathsf{Max3SAT}$

Various gapped maximization problems are known not to be $\mathbf{NP}$-hard under $\mathbf{AC}^0$ reductions, e.g., $\mathsf{Gap}_{1,\epsilon}\text{-}\mathsf{Max3SAT}$ (see, e.g., Proposition 4 of ...
Noah Singer's user avatar
6 votes
0 answers
166 views

Computing and maintaining the minimum of a set $S$ of integers while allowing updates on $S$

This question is about computing and maintaining the minimum of a set $S$ of integers while allowing updates on $S$. The computation model we are considering is the unit-cost RAM machine with linear ...
Louis's user avatar
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6 votes
0 answers
349 views

How hard is APPROXIMATE-#SAT?

It is well known that the problem of counting the satisfying assignments of SAT, namely the problem #SAT, is #P-complete. It is also suspected (somewhat less widely) that even deciding SAT should ...
squiggles's user avatar
  • 203
6 votes
0 answers
186 views

Lower bound for Yao's algorithm on general addition chains?

An addition chain of size $n$ for given integers $n_1,n_2\dots ,n_p$ is a sequence of integers $k_1,k_2\dots ,k_n$ such that $k_1=1$, for all $i$ $(2\le i\le m)$ we have $k_i=k_j+k_m$ for some $1\le ...
Danny's user avatar
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6 votes
0 answers
183 views

Converse to natural proofs theorem?

Natural proofs paper shows 'if there is a natural property not possessed by any function in P/poly then there is no $2^{n^\epsilon}$-hard PRG'. Is it easy to see the converse 'if there is no $2^{n^\...
Turbo's user avatar
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6 votes
0 answers
119 views

Lower bounds for randomized frequency estimation algorithms

Consider a stream of elements $s_1s_2\ldots s_N$. A counter-based frequency estimation algorithm uses $m$ counters and is required to answer queries of the form "How many times did $x$ appear"? It ...
R B's user avatar
  • 9,458
6 votes
0 answers
277 views

The latest concerning Valiant-Vazirani

I'm wondering what the best method obtained for the Valiant-Vazirani theorem is. We can state the following criteria: (1) First and foremost, has anyone been able to derandomize it? (2) If not, ...
Matt Groff's user avatar
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6 votes
0 answers
221 views

Lowerbounds for in-situ permutation

What is the best known lowerbound for the worst case complexity of in-situ permutation (also called in-place rearrangement)? Has there been any reported progress after the 1970's article by Knuth (...
A J's user avatar
  • 161
5 votes
0 answers
72 views

Inapproximability Results for APX-hard Geometric Optimization Problems

A lot of Geometric Optimization problems are NP-hard and APX-hard to approximate (No PTAS unless P=NP). One example of the geometric set cover problem can be found here. However, it is not easy to ...
user avatar
5 votes
0 answers
147 views

How hard is it to generate a set of relatively prime numbers between two given bounds?

Informal Question How hard is it to generate a set of relatively prime numbers between two given bounds? Decision Problem Given $a$, $b$, and $k \in \mathbb{N}$. Does there exist a set $S \...
Michael Wehar's user avatar
5 votes
0 answers
102 views

Using epsilon biased sets for circuit lower bounds

I have seen instances of how the technique of epsilon biased sets can be used to construct hard functions against a circuit class - like how in the recent paper of Kane-Williams this was used to ...
gradstudent's user avatar
  • 1,453
5 votes
0 answers
255 views

What is the status of Determinantal Complexity of Permanent

Recently Landsberg and Ressayre announced an exponential lower bound for permanent's determinantal complexity assuming certain symmetry conditions. What is the status of the problem of Permanent's ...
user avatar
5 votes
0 answers
133 views

Tools to bound the singular values of a finite sum of random matrices from below?

Matrix Chernoff bounds (see also this arXiv paper) are usually used to give upper bounds on the largest eigenvalue of a finite sum of random matrices. Sometimes it can also be used to give a lower ...
olivia's user avatar
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5 votes
0 answers
293 views

Sketch of Razborov's paper "On the method of approximations"

(The following question has bothered me for many years.) Razborov seems to have obtained some of the strongest/award winning lower bounds on circuits found in the field over many years, largely ...
vzn's user avatar
  • 11k
4 votes
0 answers
225 views

Exact lower bound on matrix multiplication

The recent publication in Nature of "Discovering faster matrix multiplication algorithms with reinforcement learning" by Fawzi et al. has shown a method for discovering fewer element ...
Mitch's user avatar
  • 905
4 votes
0 answers
84 views

Universal Relation

In the paper Tight Bounds for Lp Samplers, Finding Duplicates in Streams, and Related Problems, the authors consider the universal relation problem in 2-party communication complexity, which is ...
Theo's user avatar
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4 votes
0 answers
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Is $NEXP^{NP}$ known to not be contained in $NP/poly$?

To the best of my knowledge, it is known that $NEXP^{NP} \nsubseteq P/poly$, but it's still not known if $NEXP \nsubseteq P/poly$. For more info, see "Superpolynomial circuits, almost sparse oracles ...
Michael Wehar's user avatar
4 votes
0 answers
97 views

Sampling Functions Efficiently vs Pseudorandom Generators

Let $X$ be a set of $n$-bit Boolean functions of the form $f:\{0,1\}^n\rightarrow \{0,1\}$. For instance, $X$ could be the set of $n$-bit monotone Boolean functions, or the set of $n$-bit functions ...
verifying's user avatar
  • 1,072
4 votes
0 answers
264 views

Algebraic decision trees and adversary arguments

In the comparison tree model, we establish lower bounds on computing $\min$ and $\max$ of $n$ numbers via the adversary argument. Are there problems on which we know lower bounds in the algebraic ...
Sadguru's user avatar
  • 83
4 votes
0 answers
140 views

Natural Problems NSPACE[n] but not in DTIME[n]

It is known that $\mathrm{DTIME}[n]\subseteq \mathrm{DSPACE}[n/\log n]$. Therefore, there are languages in $\mathrm{DSPACE}[n]$ which are not in $\mathrm{DTIME}[o(n\log n)]$. Are there examples of "...
Parachutes's user avatar
4 votes
0 answers
176 views

Nondeterministic communication complexity of Hamming distance

It is something that I think should be known: what is nondeterministic communication complexity of following task: is $H(x,y) \geq k$? There is an obvious upper bound $k \log(n)$. I would expect ...
ivmihajlin's user avatar
4 votes
0 answers
248 views

One-way randomized complexity of (variants of) Gap-Hamming-Distance?

The $\textsf{GapHammingDistance}$ problem over $\{0,1\}^n$ is defined as follows: Alice (resp. Bob) is given an input $x\in\{0,1\}^n$ (resp, $y\in\{0,1\}^n$), under the promise that their Hamming ...
Clement C.'s user avatar
  • 4,471
3 votes
0 answers
50 views

Online assignment lower bound results

I am reading the following paper which presents a $(1-\epsilon)$-competitive online algorithm for the MaxMin (similar to the makespan) problem, defined as follows: a set of requests are arriving in an ...
Doc Stories's user avatar
3 votes
0 answers
168 views

Why is it difficult for $GCT$ to prove super quadratic lower bound?

We have a quadratic lower bound for the Permanent versus Determinant problem. Why is it difficult for $GCT$ to improve it?
VS.'s user avatar
  • 539
3 votes
0 answers
117 views

Why do most 0/1 matrices need linear arithmetic circuits of size $\Omega(n^2/\log(n))$?

I am reading Alon et al.'s paper Linear Circuits over $GF(2)$ and I am having trouble seeing the counting argument showing that most matrices need a circuit of size $\Omega(n^2/\log n)$. This result ...
ralphS16's user avatar
3 votes
0 answers
97 views

Lower bound for reversing a list using queues

How do you prove (or disprove) that a list of length $n$ cannot be reversed in time $o(n \log n)$ using $O(1)$ queues? Each queue is FIFO. Time refers to the number of operations on the queues. ...
Dmytro Taranovsky's user avatar
3 votes
0 answers
168 views

Circuit's with gate computing only "simple" functions

I was curious if something like that is known or was studied. Let's call a function simple if it is computable by $AC_0$ circuit of depth $\leq d$ and size $\leq n^k$ for fixed $k,d$. Now let's ...
ivmihajlin's user avatar