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@ -32,52 +32,6 @@
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@ingroup groupFilters
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@ingroup groupFilters
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*/
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*/
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/**
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@defgroup Corr Correlation
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Correlation is a mathematical operation that is similar to convolution.
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As with convolution, correlation uses two signals to produce a third signal.
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The underlying algorithms in correlation and convolution are identical except that one of the inputs is flipped in convolution.
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Correlation is commonly used to measure the similarity between two signals.
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It has applications in pattern recognition, cryptanalysis, and searching.
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The CMSIS library provides correlation functions for Q7, Q15, Q31 and floating-point data types.
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Fast versions of the Q15 and Q31 functions are also provided.
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@par Algorithm
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Let <code>a[n]</code> and <code>b[n]</code> be sequences of length <code>srcALen</code> and <code>srcBLen</code> samples respectively.
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The convolution of the two signals is denoted by
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<pre>
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c[n] = a[n] * b[n]
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</pre>
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In correlation, one of the signals is flipped in time
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<pre>
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c[n] = a[n] * b[-n]
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</pre>
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@par
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and this is mathematically defined as
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\image html CorrelateEquation.gif
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@par
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The <code>pSrcA</code> points to the first input vector of length <code>srcALen</code> and <code>pSrcB</code> points to the second input vector of length <code>srcBLen</code>.
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The result <code>c[n]</code> is of length <code>2 * max(srcALen, srcBLen) - 1</code> and is defined over the interval <code>n=0, 1, 2, ..., (2 * max(srcALen, srcBLen) - 2)</code>.
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The output result is written to <code>pDst</code> and the calling function must allocate <code>2 * max(srcALen, srcBLen) - 1</code> words for the result.
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@note
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The <code>pDst</code> should be initialized to all zeros before being used.
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@par Fixed-Point Behavior
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Correlation requires summing up a large number of intermediate products.
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As such, the Q7, Q15, and Q31 functions run a risk of overflow and saturation.
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Refer to the function specific documentation below for further details of the particular algorithm used.
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@par Fast Versions
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Fast versions are supported for Q31 and Q15. Cycles for Fast versions are less compared to Q31 and Q15 of correlate and the design requires
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the input signals should be scaled down to avoid intermediate overflows.
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@par Opt Versions
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Opt versions are supported for Q15 and Q7. Design uses internal scratch buffer for getting good optimisation.
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These versions are optimised in cycles and consumes more memory (Scratch memory) compared to Q15 and Q7 versions of correlate
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*/
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/**
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/**
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@addtogroup Corr
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@addtogroup Corr
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@{
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@{
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@ -209,7 +163,7 @@ void arm_correlate_f64(
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while (blockSize1 > 0U)
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while (blockSize1 > 0U)
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{
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{
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/* Accumulator is made zero for every iteration */
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/* Accumulator is made zero for every iteration */
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sum = 0.0f;
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sum = 0.;
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/* Initialize k with number of samples */
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/* Initialize k with number of samples */
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k = count;
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k = count;
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@ -274,7 +228,7 @@ void arm_correlate_f64(
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while (blkCnt > 0U)
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while (blkCnt > 0U)
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{
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{
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/* Accumulator is made zero for every iteration */
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/* Accumulator is made zero for every iteration */
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sum = 0.0f;
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sum = 0.;
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/* Initialize blkCnt with number of samples */
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/* Initialize blkCnt with number of samples */
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k = srcBLen;
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k = srcBLen;
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@ -314,7 +268,7 @@ void arm_correlate_f64(
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while (blkCnt > 0U)
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while (blkCnt > 0U)
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{
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{
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/* Accumulator is made zero for every iteration */
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/* Accumulator is made zero for every iteration */
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sum = 0.0f;
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sum = 0.;
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/* Loop over srcBLen */
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/* Loop over srcBLen */
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k = srcBLen;
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k = srcBLen;
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@ -375,7 +329,7 @@ void arm_correlate_f64(
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while (blockSize3 > 0U)
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while (blockSize3 > 0U)
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{
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{
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/* Accumulator is made zero for every iteration */
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/* Accumulator is made zero for every iteration */
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sum = 0.0f;
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sum = 0.;
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/* Initialize blkCnt with number of samples */
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/* Initialize blkCnt with number of samples */
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k = count;
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k = count;
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JbR
4 years ago
committed by
Christophe Favergeon