Method of input data compression, associated computer program product, computer system and extraction method

A computer program product comprising software instructions which, when executed by a computer system, implement a method of input data compression performed by at least one core communicating with a central memory, the core being associated to an operating cache memory able to store data items, and comprising a plurality of vector registers able to store data items to be processed, each vector register presenting a predetermined register length, the operating cache memory comprising a plurality of cache lines, each cache line presenting a predetermined cache line length which is a multiple of the register length;

• the input data presents a two-dimensional input array formed by a plurality data items stored contiguously in the central memory according to a contiguous direction;
• the method comprising a step of two-dimensional wavelet transform implemented using a low band-pass filter vector of dimension N and a high band-pass filter vector of dimension N, said step comprising the following sub-steps:
• A) forming from the input array at least one tile comprising a plurality of consecutive data block columns, each data block column being formed by a plurality of lines of consecutive data items according to the contiguous direction, the length of each line being a multiple of the cache line length;
• C) for the or each tile, processing each data block column and for each data block column, computing dot products between the low band-pass or high band-pass filter vector and each group of N lines using fused multiply-add instructions for the core,
• wherein one tile is formed during the sub-step A), said tile corresponding to said two-dimensional input array,
• wherein the step of two-dimensional wavelet transform further comprises a sub-step D′) of transposing the two-dimensional input array, the sub-steps A) and C) being performed before the sub-step D′) for a non-transposed input array and then, after the sub-step D′) for a transposed input array.

A computer system for input data compression comprising a central memory and at least one core communicating with the central memory;

• the core being associated to an operating cache memory able to store data items, and comprising a plurality of vector registers able to store data items to be processed, each vector register presenting a predetermined register length, the operating cache memory comprising a plurality of cache lines, each cache line presenting a predetermined cache line length which is a multiple of the register length;
• the core being configured to carry out a method of input data compression;
• the input data presents a two-dimensional input array formed by a plurality data items stored contiguously in the central memory according to a contiguous direction;
• the method comprising a step of two-dimensional wavelet transform implemented using a low band-pass filter vector of dimension N and a high band-pass filter vector of dimension N, said step comprising the following sub-steps:
• A) forming from the input array at least one tile comprising a plurality of consecutive data block columns, each data block column being formed by a plurality of lines of consecutive data items according to the contiguous direction, the length of each line being a multiple of the cache line length;
• C) for the or each tile, processing each data block column and for each data block column, computing dot products between the low band-pass or high band-pass filter vector and each group of N lines using fused multiply-add instructions for the core,
• wherein one tile is formed during the sub-step A), said tile corresponding to said two-dimensional input array,
• wherein the step of two-dimensional wavelet transform further comprises a sub-step D′) of transposing the two-dimensional input array, the sub-steps A) and C) being performed before the sub-step D′) for a non-transposed input array and then, after the sub-step D′) for a transposed input array.