prevent constructing `MatrixSliceMutMN` for which disjoint indices may alias the same linear index
Fixes #486.
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@ -37,6 +37,7 @@ generic-array = "0.12"
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rand = { version = "0.6", default-features = false }
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num-traits = { version = "0.2", default-features = false }
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num-complex = { version = "0.2", default-features = false }
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num-rational = { version = "0.2", default-features = false }
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approx = { version = "0.3", default-features = false }
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alga = { version = "0.9", default-features = false }
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matrixmultiply = { version = "0.2", optional = true }
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@ -2,6 +2,7 @@ use crate::base::dimension::{Dim, DimName, Dynamic, U1};
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use crate::base::matrix_slice::{SliceStorage, SliceStorageMut};
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use crate::base::{MatrixSliceMN, MatrixSliceMutMN, Scalar};
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use num_rational::Ratio;
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/*
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*
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* Slice constructors.
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@ -107,6 +108,37 @@ impl<'a, N: Scalar, R: Dim, C: Dim, RStride: Dim, CStride: Dim>
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"Matrix slice: input data buffer to small."
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);
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assert!({
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let nrows = nrows.value();
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let ncols = ncols.value();
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let rstride = rstride.value();
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let cstride = cstride.value();
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// `Storage::linear_index`
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let index = |i, j| (i * rstride) + (j * cstride);
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// The final condition of each arm is an expression in the form:
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// index(i₀, j₀) != index(i₁, j₁)
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// If this expression is `false`, then the values (i₀, j₀)
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// and (i₁, j₁) are concrete examples of indices that would
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// collide if the matrix was actually constructed.
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nrows * ncols <= 1 ||
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match (rstride, cstride) {
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(0, 0) => index(0, 0) != index(nrows - 1, ncols - 1),
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(0, _) => nrows <= 1 || index(0, 0) != index(nrows - 1, 0),
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(_, 0) => ncols <= 1 || index(0, 0) != index(0, ncols - 1),
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(_, _) => {
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let ratio = Ratio::new(rstride, cstride);
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let numer = *ratio.numer();
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let denom = *ratio.denom();
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nrows <= denom || ncols <= numer
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|| index(0, numer) != index(denom, 0)
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}
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}
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},
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"Matrix slice: dimensions and strides result in aliased indices.");
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unsafe {
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Self::from_slice_with_strides_generic_unchecked(data, 0, nrows, ncols, rstride, cstride)
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}
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@ -112,6 +112,7 @@ extern crate generic_array;
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extern crate matrixmultiply;
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extern crate num_complex;
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extern crate num_traits as num;
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extern crate num_rational;
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extern crate rand;
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extern crate typenum;
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