Difference between revisions of "CodeCompositionIneffective"
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| + | [[Category:Performance Pattern]] | ||
== Description == | == Description == | ||
| + | The pattern "Code composition - inefficient instructions" describes the usage of one kind of instructions although there exists a better kind, e.g. scalar vs. vectorized FP instructions. | ||
== Symptoms == | == Symptoms == | ||
| + | Like [[InstructionOverhead|Instruction Overhead]]. | ||
| + | |||
| + | For a piece of high-level code, the compiler outputs a lot of instructions although is could be done in less. One common example are non-vectorized instructions. | ||
== Detection == | == Detection == | ||
| + | For code with FP arithmetic, check whether scalar instructions are dominating in data parallel loops. | ||
| + | |||
| + | LIKWID groups: FLOPS_DP, FLOPS_SP (see vectorization ratio) | ||
== Possible optimizations and/or fixes == | == Possible optimizations and/or fixes == | ||
| + | * Try to give hints to the compiler so that it can use the more efficient instructions. (E.g. <code>#pragma simd</code>) | ||
| + | * Reorganize access pattern | ||
| + | * Avoid loop carried dependecies | ||
== Applicable applications or algorithms or kernels == | == Applicable applications or algorithms or kernels == | ||
Latest revision as of 16:17, 3 September 2019
Description
The pattern "Code composition - inefficient instructions" describes the usage of one kind of instructions although there exists a better kind, e.g. scalar vs. vectorized FP instructions.
Symptoms
Like Instruction Overhead.
For a piece of high-level code, the compiler outputs a lot of instructions although is could be done in less. One common example are non-vectorized instructions.
Detection
For code with FP arithmetic, check whether scalar instructions are dominating in data parallel loops.
LIKWID groups: FLOPS_DP, FLOPS_SP (see vectorization ratio)
Possible optimizations and/or fixes
- Try to give hints to the compiler so that it can use the more efficient instructions. (E.g.
#pragma simd) - Reorganize access pattern
- Avoid loop carried dependecies