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IA-32 Intel® Architecture Optimization
3-32
Strip Mining
Strip mining, also known as loop sectioning, is a loop transformation
technique for enabling SIMD-encodings of loops, as well as providing a
means of improving memory performance. First introduced for
vectorizers, this technique consists of the generation of code when each
vector operation is done for a size less than or equal to the maximum
vector length on a given vector machine. By fragmenting a large loop
into smaller segments or strips, this technique transforms the loop
structure twofold:
• It increases the temporal and spatial locality in the data cache if the
data are reusable in different passes of an algorithm.
• It reduces the number of iterations of the loop by a factor of the
length of each “vector,” or number of operations being performed
per SIMD operation. In the case of Streaming SIMD Extensions,
this vector or strip-length is reduced by 4 times: four floating-point
data items per single Streaming SIMD Extensions single-precision
floating-point SIMD operation are processed. Consider
Example 3-18.
Example 3-18 Pseudo-code Before Strip Mining
typedef struct _VERTEX {
float x, y, z, nx, ny, nz, u, v;
} Vertex_rec;
main()
{
Vertex_rec v[Num];
....
for (i=0; i<Num; i++) {
Transform(v[i]);
}
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