check for invalid shapes in strassen multiplication (#208)

* check for invalid shapes in strassen multiplication
Strassen multiplication is only possible when the matrix dimensions are a power of two.

* reorder variables in assert condition

* fix indentation

Author: rakki-18

src/Math-Matrix/PMMatrix.class.st

@@ -950,8 +950,13 @@ PMMatrix >> squared [
 PMMatrix >> strassenProductWithMatrix: aMatrix [
 	"Private"
 	| matrixSplit selfSplit p1 p2 p3 p4 p5 p6 p7 |
+
 	( self numberOfRows > 2 and: [ self numberOfColumns > 2])
 		ifFalse:[ ^self class rows: ( aMatrix rowsCollect: [ :row | self columnsCollect: [ :col | row * col]])].
+	
+	self assert: [ self numberOfRows isPowerOfTwo and: self numberOfColumns isPowerOfTwo  ] description: 'Matrix size should be a power of two'.
+	self assert: [ aMatrix numberOfRows isPowerOfTwo and: aMatrix numberOfColumns isPowerOfTwo  ] description: 'Matrix size should be a power of two'.
+		
 	selfSplit := self split.
 	matrixSplit := aMatrix split.
 	p1 := ( ( selfSplit at: 2) - ( selfSplit at: 4)) strassenProductWithMatrix: ( matrixSplit at: 1).

src/Math-Tests-Matrix/PMMatrixTest.class.st

@@ -737,6 +737,29 @@ PMMatrixTest >> testSkalarMultiplication [
 	self assert: r class equals: PMSymmetricMatrix
 ]
 
+{ #category : #tests }
+PMMatrixTest >> testStrassenProductWithMatrix [
+		
+	| aPMMatrix expected strassenProduct |
+	
+	aPMMatrix := PMMatrix rows: #( (1 2 3 4) (1 0 1 2) (2 3 1 4) (4 3 2 2)).
+	expected  := PMMatrix rows: #( (30 12 27 24) (12 6 11 10) (27 11 30 27) (24 10 27 33)).
+	strassenProduct := aPMMatrix transpose strassenProductWithMatrix: aPMMatrix.
+	self assert: strassenProduct equals: expected.
+]
+
+{ #category : #tests }
+PMMatrixTest >> testStrassenProductWithMatrixWithInvalidShapes [
+		
+	| aPMMatrix |
+	
+	"all the dimension of the matrices should be a power of 2 for strassen multiplication"
+	aPMMatrix := PMMatrix rows: #( (1 2 3) (1 0 1) (2 3 1) (2 0 1)).
+	
+	self should: [ aPMMatrix strassenProductWithMatrix: aPMMatrix transpose ] raise: AssertionFailure.
+
+]
+
 { #category : #tests }
 PMMatrixTest >> testSymmetric [
 |a m|