Pred`i*ca"tion (preh' dih kay' shuhn), n.


The conditional execution of an instruction.

In deeply pipelined architectures such as Texas Instruments' C6000 (DSPs) and Intel's P6 (Pentium III processors) and IA-64 (Itanium processors), branches and jumps have so many delay slots (or, in machines with interlocked pipeline stages, so much penalty for misprediction) that you don't want to branch except when absolutely necessary. Predication avoids many branches by executing a given instruction if and only if a given register is (non)zero, eliminating a large fraction of branches entirely and making basic blocks larger. BIG speed win.

For example, C6000-series processors can conditionally execute an instruction based on the zeroness of register A1, A2, B0, B1, or B2, denoted by a prefix in square brackets before the instruction. The common instruction

[b0] sub .s2 b0, 1, b0
uses the S2 functional unit to decrement the B0 register if it's not already 0. (To specify execution if a register IS zero, use a bang to take the logical NOT: [!b0] instead of [b0].)

A related optimization technique, speculation, executes both paths of a branch simultaneously in a branch's delay slots; the code after the branch adjusts the results as necessary, discarding "wrong" answers.

For an explanation of features that lessen the impact of branches on newer architectures, see

I - Inquiry

What is the word you use when you want to describe wanting to say something that may or may not happen in the future depending upon whether or not you want it to but you might not be entirely in control of it anyway?
What is that word?
Is it not a word?
It should be.

II - Meditation

There is a moment deeper than breathing
when the archer may become one with the bow;
the archer becomes one with the arrow; one with the target;
no more are the bow, the arrow, the target; and the archer becomes archery itself.
At such moment need the arrow be loosed from the bow upon the target?

III - History

There is a bullet fired you cannot dodge, proximity notwithstanding. Jaromir Hladik is brought into the courtyard, and, after a cigarette with which to pass the time, stands before his firing squad. Like a macabre photographer they ask him to adjust his disposition with regard to the wall behind him. His bullets might be allowed to bury themselves there, but his blood may not stain it. And yet, there is a space of time, perhaps even a complete year, before the volley is fired. In some ways, this is a Vindication of Eternity, that time was allotted to complete his drama in verse, The Enemies.

IV - Prophecy

Strains from Carmen hover at the edge of my hearing. The trumpets announce the entrance of the train: the capeadores, the mounted picadores, the brave banderilleros, and finally the lithe supple dancer's form of the toreador. My matador. The one who shall slay me. Perhaps it is already done.

Pred`i*ca"tion (?), n. [L. praedicatio: cf. F. pr'edication.]


The act of predicating, or of affirming one thing of another; affirmation; assertion.




[Obs. or Scot.]



© Webster 1913.

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