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Cost
- A block size is a property of the machine
- Doing it twice
- Memory bought with messages
- The message and the word
- The order the products are taken in
- The same arithmetic at a different price
- The last digit is the cheapest
- The recursion that was never told the memory
- A reduction that changes the order
- Where the format starts paying
- The block size a recursion still has
- The plan that was right at rank four
- A ceiling is not a target
- The search that got worse as it widened
- A beam ranked on what remains
- Widen the beam where the ranking is right
- The leaf that sits on the edge
Arithmetic
- A bound that is proved
- A coin flip that fixes the average
- A norm that overflows before it is a norm
- Eight bits, and a format that breaks the rules
- One exponent for thirty-two numbers
- Proving the answer is in the box
- The direction the error leans
- The numbers below the smallest one
- The other half of a format
- Where the box is cut
- Cancellation takes the answer, not a digit
- The order they are added in
- What a float can hold
- Nine steps of pessimism
- A bit buys an octave
- Buying the accuracy back
- The units that overflow before the answer does
- Three walks and one bound
- Where the hardware went
Spectra
- A condition number for one eigenvalue
- An eigenvalue one vector cannot see
- An eigenvalue with no value
- How wide the block should be
- The algorithm the libraries actually run
- The best approximation there is
- The form a real matrix can reach
- The form that makes it affordable
- The gap decides the eigenvector
- The plane survives what its vectors do not
- The vector was what was wanted
- Two matrices and one problem
- Two shifts that are never formed
- An eigenvalue count that cannot be slightly wrong
- Symmetry is worth more than precision
- An eigenvalue that arrives twice
- The largest gap is inside the null space
- The error the method already knows
- The same budget, spent five ways
- A function of a matrix is not a function of its entries
- A good curve and a bad verdict
- A problem with no answer
- A spectral radius that grows first
- A threshold the matrix does not set
- Accurate is not a property of a method
- Keeping the vectors, and losing the bound
- Rank is a decision
- Restarting is a filter
- Small compared to what
- The cheap rank and what it cannot see
- The eigenvalues that are not there
- The series that has to be squared back
Leastsquares
- A correction cheaper than the problem
- The observation that cannot be removed
- The projection and the right angle
- The road that squares the problem
- The valley with no bottom
- A constraint is a weight at infinity
- Influence is decided before the data
- A basis built from the points
- The two numbers a caller has
- When the matrix is wrong too
- Two observations that hide each other
- One minus a leverage is a subtraction
- The reference was a method
- The condition number that does not know
- Feasible and wrong
- The factor a sparse code keeps anyway
- The weight the factor met first
Iterative
- A direction the smoother cannot see
- Aggregating what the matrix calls strong
- A hierarchy with no grid behind it
- An operator with no entries
- A rate that does not notice the size
- Exact along one axis
- One sequence and two recurrences
- Smoothing a whole line at once
- The coarse grid the matrix chooses
- The diffusion that makes the answer exact
- The formula that was already optimal
- The number that is re-derived
- The stencil that is not symmetric
- A Krylov space for a problem that is not linear
- Changing the condition number on purpose
- The coarse problem is a different problem
- A run that is over at step five
- A smoother that stops being one
- How much direction there was to lose
- A different equation on every grid
- A parameter that is also a price
- The switch does not know which side is better
- The answer that arrives when the space runs out
- A walk needs a length
- A proof that does not ask how large the matrix is
- A rate that is known in advance
- An iterate that must be made smaller
- An orthogonalisation nobody calls one
- Coarsening in one direction only
- The certificate that arrives soonest is worth least
- The direction the diffusion does not go
- The division that cannot be done
- The error smoothing cannot reach
- The rate the condition number predicts
- The residual the method reports
- The same problem on a coarser grid
- The same zero, and nothing was found
- The spectrum that predicts nothing
- The zero that means it is finished
Structure
- A limit the matrix never reaches
- An equation whose unknown is a matrix
- The matrix that is one row
- Two dimensions, and the cluster that thins
- A perturbation that keeps the symmetry
- The elimination the matrix does not need
- A speedup with a ceiling of its own
- The number that cannot rank them
- A nearby problem of the wrong kind
- A preconditioner that changes sign
- Four orders of conditioning, and four steps
- The circulant that cannot be indefinite
- The condition number of the model
- The circulant the problem did not contain
- Two near-zeros cost less than one
- The correction lost to its own two-by-two solve
- A zero no twist can step around
Error
- An answer that is known
- The exact answer to a nearby problem
- The zero you are allowed to write
- Three errors and one number
- A small residual is not a small error
- The condition number is an amplifier
- The tail a sample never reaches
- A tolerance is priced by the problem
- A condition number scaling cannot move
- A tensor that cannot be decomposed
- An accuracy that is a backward error
- An estimate that can be fooled
- Deciding that a zero has arrived
- The fifth author
- The number that decides nothing
- The roots are not the coefficients
- The units the matrix is measured in
- Two condition numbers of one matrix
Combination
- A parameter chosen on a smaller problem
- Four knobs and one floor
- The part of a solver that may be rounded
- An answer that changes with the seed
- An expiry date the noise does not move
- A step that is not a unit of work
- The method that cannot use a smooth answer
- A preconditioner that arrives past the answer
- A parameter that counts steps
- The step that stops mattering
- What a cheap preconditioner has to leave alone
- A stopping rule that follows the run it is given
- The rule that is wrong in the right direction
- The parameter neither knob is
- A count that marks the edge and not the pace
- The shift had an edge, and the approximation moved it
- One arc, and what each filter pays to be on it
Tensor
- A rank that is not a property of the tensor
- A compression of 10¹⁴ that still does not fit
- Five indices are cheaper than two
- A decomposition made only of SVDs
- A factorisation that is unique for once
- A nearest point that is not there
- A solve that is d decompositions
- An index that is a pair
- An iteration that walks out of the set
- The digit that costs more than the tensor
- The format that does not notice the dimension
- The orthogonality that cannot be diagonal
- The test that is a deadline
- The repair that costs exactly itself
- One term too many
- The rank a sweep can vouch for
- A fit that has an answer and cannot stop
Orthogonality
- A reflection cannot stop being one
- Orthogonal is a number
- Two Gram–Schmidts
- A test with no answer in it
- The right-hand side as one more column
- A stable block is not a stable basis
- A rotation that comes back mirrored
- An iteration that only multiplies
- The nearest orthogonal matrix
- The tree the resistances choose
- Spread resistances make the loops easy
- The basis nobody chose on purpose
- One number that has to be right
- A triangle where the scalar was
- Five precise points are five points
- A mirror decided in the thin directions
- What the appended block inherits
Elimination
- A rule that is correct and unusable
- Elimination is a sequence of choices
- The bound that is never attained
- The swap that is not optional
- The gap refinement can close
- A pivot that searches one row and one column
- A factorisation with nothing to pivot for
- The inverse that is never formed
- The pivot that reads the units
- When symmetry is not enough
- A worst case is as fragile as its margin
- The growth a boundary-value problem supplies
- Which of the choices is doing the work
- The order the greedy rule cannot choose
- Noise the growth amplifies
- A margin the factorisation records
- A threshold that holds the growth still
Sequence
- A tolerance that reads its own residual
- Stable once, and three thousand times
- The accuracy that is thrown away
- The problem that arrives again
- What a rebuild is worth
- The penalty for keeping it is a ratio
- The repair the drift did not need
- A factorisation kept past its date
- What survives one step of the barrier
- Where the drift lands
- The order a batch arrives in
- A warm start is degree zero
- A guess worth two per cent
- One line that buys a quarter of the run
- A straight path has nothing for a parabola to fit
- The degree the history chooses
- The answer the last window left
Sparsity
- Structure and stability stop being separable
- The factor is not sparse
- The order decides the memory
- The order that was right last time
- Two ends of the same arrow
- What the symbolic phase can only bound
- A threshold between fill and growth
- The cliff behind the count
- An ordering that does not wait for the numbers
- The fill that is not independent
- The least fill there is
- An ordering that buys processors, not time
- Two minima that are one minimum
- The depth that is worse than both ends
- The column that was never fixed
- How few columns the search needs
- The freedom a symmetric factorisation does not have
Regularisation
- The basis decides what a filter is
- When the answer is a choice
- Where the answer stops being in the data
- The grid was the first filter
- Thirty-two coefficients instead of a noise level
- One draw in twenty
- The corner reads the norm it is drawn in
- A second blur, narrower than the first
- Choosing without knowing
- Noise that spares the answer and fools the rules
- Where the grid hands over to λ
- A better discretisation is a weaker filter
- A rule that has to be told how good its answer will be
- A second penalty is not a second parameter
- The grid on which the discretisation stops mattering
- A corner the penalty can afford
- The data count their dimensions, not the step's
Hierarchy
- The kernel with nothing to compress
- The same matrix, numbered twice
- The size the rank does not notice
- The test that costs what it saves
- A knob calibrated in residuals
- The offset that moved the slope
- The count that is not the budget
- A block nobody can call sparse
- A rank that is a number of digits
- The accuracy worth paying for
- The knob that moved two things
- The rounding that was not the problem
- Which pairs are allowed to be small
- The partition that does not move
- Two knobs on one number
- A geometry setting that is a second accuracy
- A second objective that is the first one doubled
- A prediction that arrives a decade late
Randomised
- The sketch that is not the answer
- The sketch that is spent
- The half of a problem a sketch may touch
- Counting what is inside a circle
- The dimension does not appear
- What a single draw cannot report
- A bound that holds with probability
- A rate that belongs to the matrix
- Built from products alone
- Counting what cannot be looked at
- Randomisation does not create structure
- Sketching what is never unfolded
- A rule that reads only its own probes
- The split nobody is in a position to choose
- The rank a certificate charges
- A sketch that finds the columns it can see
- The miss a normal table already priced
Constraint
- The zero that is not a missing entry
- Two ways to remove a constraint
- Three eigenvalues, and two are the golden ratio
- A preconditioner that need not know the constraint
- A condition number sent to infinity
- A minimum the Hessian cannot see
- The active set before the digits
- One eigenvalue and two steps
- Where the augmentation puts the cost
- The regularisation that legalises every order
- A shift that certifies a saddle
- The perturbation that does the work
- Two repairs for one symptom
- A test with no tolerance in it
- The shift that stops at the first right count
- A constraint the count stops seeing
- A loop that asks the null space why
Polynomial
- A matrix that depends on its own eigenvalue
- The scaling that buys ten orders
- Six routes to one spectrum
- A spectrum that comes in reciprocal pairs
- A problem with infinitely many eigenvalues
- The problem the solver was actually given
- An error committed before the arithmetic
- The eigenvalues that are answers to nothing
- The points the algorithm chose
- A backward-stable answer to a problem nobody asked
- One mass removed, and one eigenvalue gone
- The number that moves when the problem does
- Where a contour's budget should go
- A ceiling with a knob on it
- A class a longer chain takes away
- A perturbation that moves every coefficient
- An estimate that does not move
- Every eigenvalue real, and a test that says so
- The conditioning that rises with the ceiling
- Two approximants and one matrix size
Reduction
- A model that is a rational function
- The bound that is known in advance
- The product nobody had to form
- Exact at the points that were named
- A basis that is the same subspace and not the same thing
- Interpolating at the model’s own poles
- Where to put the poles of a rational function
- A model that cannot be run
- A model with no matrices behind it
- The state that is removed is not a mode
- The definition asks for more of what defeats it
- Bracketing an error nobody can measure
- A condition number that is not the model's
- Why a Gramian can be truncated at all
- Half the conditions and a certificate
- A certificate written in coordinates
- The inner product the mesh already computed
Machine
- The same program, twice
- A bound every answer satisfies
- Where the disagreement comes from
- The vector that hides it
- The sum that cannot be wrong
- What determinism costs
- Accuracy and agreement are different properties
- A matrix that is definite on one machine
- A square that evaluates negative
- A rank that depends on the thread count
- The length that changes the kernel
- What a regression test can ask for
- An inner product with no fixed sign
- The variation that comes with a seed
- Two machines, one certificate
- One multiply the compiler removed
- The licence is not the boundary
- The reading that never moves
- A stopping test is a race
- The tolerance that buys no agreement
Graph
- A matrix with no numbers in it
- The vertex nobody solves for
- A partition decided in the last digit
- A ranking that is an eigenvector
- The rate is the second eigenvalue
- A chain with no stationary vector
- An eigenvector that must not change sign
- A ranking whose order is not determined
- A distance computed by a solve
- A graph with a tenth of the edges
- Eliminating a vertex is a graph operation
- A count that comes out of a determinant
- The spectrum is not the graph
- A conductance the arcs do not measure
- Two Laplacians of one graph
- A bound with a square root in it
- A Laplacian that is not symmetric
- A preconditioner that is a tree
- The vector that has to be rounded
Exact
- An answer with no error in it
- Every intermediate is a minor
- How many primes the answer needs
- A prime that divides the answer
- A fraction recovered from one remainder
- The rank depends on the ring
- An exact answer to a measured problem
- The answer is longer than the question
- A basis that describes its lattice badly
- What a determinant does not determine
- Rounding a coordinate in the wrong basis
- The knob and the rounding
- A relation among digits that were not there
- A bound on every intermediate at once
- Three orders and one last entry
- The room a relation has to stand out
- Two precisions guard the other edge